Bean Validation specification

Bean Validation Expert Group

Emmanuel Bernard

Red Hat, Inc.

1.1 Final

2013-04-10


Table of Contents

1. Introduction
1.1. Expert group
1.2. Specification goals
1.3. Required Java version
1.4. How this document is organized
1.5. How to comment
2. What's new in 1.1
2.1. Openness
2.2. Dependency injection
2.3. Method validation
2.4. Integration with Context and Dependency Injection
2.5. Group conversion
2.6. Message interpolation via the unified expression language
2.7. Others
3. Constraint Definition
3.1. Constraint annotation
3.1.1. Constraint definition properties
3.1.1.1. message
3.1.1.2. groups
3.1.1.3. payload
3.1.1.4. validationAppliesTo
3.1.1.5. Constraint specific parameter
3.1.2. Examples
3.2. Applying multiple constraints of the same type
3.3. Constraint composition
3.4. Constraint validation implementation
3.4.1. Examples
3.5. The ConstraintValidatorFactory
4. Constraint declaration and validation process
4.1. Requirements on classes to be validated
4.1.1. Object validation
4.1.2. Field and property validation
4.1.3. Graph validation
4.2. Constraint declaration
4.3. Inheritance (interface and superclass)
4.4. Group and group sequence
4.4.1. Group inheritance
4.4.2. Group sequence
4.4.3. Redefining the Default group for a class
4.4.4. Implicit grouping
4.4.5. Group conversion
4.4.5.1. Group conversion examples
4.4.6. Formal group definitions
4.5. Method and constructor constraints
4.5.1. Requirements on methods to be validated
4.5.2. Declaring parameter constraints
4.5.2.1. Cross-parameter constraints
4.5.2.2. Naming parameters
4.5.3. Declaring return value constraints
4.5.4. Marking parameters and return values for cascaded validation
4.5.5. Method constraints in inheritance hierarchies
4.5.5.1. Examples
4.6. Validation routine
4.6.1. Object graph validation
4.6.2. Method and constructor validation
4.6.3. Traversable property
4.6.3.1. Examples
4.6.4. ConstraintValidator resolution algorithm
4.7. Examples
5. Validation APIs
5.1. Validator API
5.1.1. Validation methods
5.1.1.1. Examples
5.1.2. Methods for validating method and constructor constraints
5.1.2.1. Examples
5.1.3. groups
5.1.3.1. Examples
5.2. ConstraintViolation
5.2.1. Examples
5.2.2. Examples for method and constructor constraint violations
5.3. Message interpolation
5.3.1. Default message interpolation
5.3.1.1. Default message interpolation algorithm
5.3.1.2. Locale for default message interpolation
5.3.1.3. Message expressions using Expression Language (EL)
5.3.2. Custom message interpolation
5.3.3. Examples
5.4. Triggering method validation
5.5. Bootstrapping
5.5.1. Examples
5.5.2. ValidatorFactory
5.5.3. Configuration
5.5.4. ValidationProvider and ValidationProviderResolver
5.5.4.1. ValidationProviderResolver
5.5.4.2. ValidationProvider
5.5.5. Validation
5.5.6. XML configuration: META-INF/validation.xml
5.5.7. Bootstrapping considerations
6. Constraint metadata request APIs
6.1. Validator
6.2. ElementDescriptor
6.3. BeanDescriptor
6.4. CascadableDescriptor
6.5. GroupConversionDescriptor
6.6. PropertyDescriptor
6.7. ExecutableDescriptor, MethodDescriptor and ConstructorDescriptor
6.8. ParameterDescriptor
6.9. CrossParameterDescriptor
6.10. ReturnValueDescriptor
6.11. ConstraintDescriptor
6.12. Example
7. Built-in Constraint definitions
8. XML deployment descriptor
8.1. Constraint definition and declaration
8.1.1. Constraint declaration in XML
8.1.1.1. Class-level overriding
8.1.1.2. Field-level overriding
8.1.1.3. Property-level overriding
8.1.1.4. Constructor-level overriding
8.1.1.5. Method-level overriding
8.1.1.6. Constraint declaration
8.1.1.7. Declaration of group conversions
8.1.2. Overriding constraint definitions in XML
8.1.3. Converting the string representation of a value
8.1.4. XML Schema
8.2. Configuration schema
9. Exception model
9.1. Error report: ConstraintViolationException
9.2. Constraint definition: ConstraintDefinitionException
9.3. Constraint declaration: ConstraintDeclarationException and UnexpectedTypeException
9.4. Group definition: GroupDefinitionException
10. Integration
10.1. General requirements
10.1.1. Objects lifecycle
10.1.2. Method and constructor validation
10.1.2.1. Examples
10.2. Java EE
10.3. Context and Dependency Injection (CDI) integration
10.3.1. ValidatorFactory and Validator
10.3.2. ConstraintValidatorFactory, MessageInterpolator, ParameterNameProvider and TraversableResolver
10.3.3. Method and constructor validation
10.4. Java Persistence 2.0 integration
10.5. Java Server Faces 2.0 integration
10.6. JAX-RS 2 integration
A. Terminology
B. Standard ResourceBundle messages
C. Java Persistence 2.0 and schema generation
D. Changelog

Chapter 1. Introduction

This document is the specification of the Java API for JavaBean validation in Java EE and Java SE. The technical objective of this work is to provide an object level constraint declaration and validation facility for the Java application developer, as well as a constraint metadata repository and query API.

It also offers method and constructor validation facilities to ensure constraints on their parameters and return values.

1.1. Expert group

This work has been conducted as part of JSR 349 and formerly JSR 303 under the Java Community Process Program. This specification is the result of the collaborative work of the members of the JSR 349 Expert Group and the community at large. The following persons have actively contributed to Bean Validation 1.1 in alphabetical order:

  • Matt Benson

  • Paul Benedict

  • Emmanuel Bernard (Red Hat, Inc.) - Specification Lead

  • Edward Burns (Oracle)

  • Peter Davis

  • Linda DeMichiel (Oracle)

  • Hardy Ferentschik (Red Hat, Inc.)

  • Antonio Goncalves

  • Cemalettin Koç

  • Rich Midwinter

  • Gunnar Morling (individual then Red Hat, Inc.)

  • Pete Muir (Red Hat, Inc.)

  • Michael Nascimento Santos

  • Gerhard Petracek

  • Kevin Pollet (SERLI)

  • Jagadish Prasath Ramu (Oracle)

  • Bill Shannon (Oracle)

  • Sebastian Thomschke

Former expert group members of JSR-303 in alphabetical order are:

  • Geert Bevin

  • Emmanuel Bernard (Red Hat, Inc.) - Specification Lead

  • Uri Boness

  • Erik Brakkee (Ericsson AB)

  • Ed Burns (Sun Microsystems, Inc.)

  • Jason Carreira

  • Robert Clevenger (Oracle - retired)

  • Linda DeMichiel (Sun Microsystems, Inc.)

  • Tim Fennel

  • Bharath Ganesh (Pramati Technologies)

  • Romain Guy (Google Inc.)

  • Robert Harrop

  • Jacob J. Hookom

  • Bob Lee (Google Inc.)

  • Craig R. McClanahan (Sun Microsystems, Inc.)

  • Niall K. Pemberton

  • Steve Peterson

  • Dhanji R. Prasanna (Google Inc., formerly individual)

  • Gerhard Petracek

  • Matt Raible

  • Michael Nascimento Santos

  • Sebastian Thomschke

  • Jon Wetherbee (Oracle)

1.2. Specification goals

Validating data is a common task that occurs throughout an application, from the presentation layer to the persistence layer. Often the same validation logic is implemented in each layer, proving to be time consuming and error-prone. To avoid duplication of these validations in each layer, developers often bundle validation logic directly into the domain model, cluttering domain classes with validation code that is, in fact, metadata about the class itself.

This JSR defines a metadata model and API for JavaBean validation. The default metadata source is annotations, with the ability to override and extend the meta-data through the use of XML validation descriptors.

The validation API developed by this JSR is not intended for use in any one tier or programming model. It is specifically not tied to either the web tier or the persistence tier, and is available for both server-side application programming, as well as rich client Swing application developers. This API is seen as a general extension to the JavaBeans object model, and as such is expected to be used as a core component in other specifications. Ease of use and flexibility have influenced the design of this specification.

As of version 1.1, Bean Validation constraints can also be applied to the parameters and return values of methods of arbitrary Java types. Thus the Bean Validation API can be used to describe and validate the contract (comprising pre- and postconditions) applying to a given method ("Programming by Contract", PbC). Note that it is not the goal of this specification to develop a fully-fledged PbC solution but rather an easy-to-use facility satisfying the most common needs related to applying constraints to method parameters and return values, based on the proven concepts of the Bean Validation API.

1.3. Required Java version

The specification uses Java 6.0 language features. There is no requirement that implementations be compatible with Java language versions prior to 6.0.

1.4. How this document is organized

This document describes each aspect of the bean validation specification in a separate chapter. One should remember that the specification is a consistent whole.

Chapter 3, Constraint Definition describes how constraints are defined.

Chapter 4, Constraint declaration and validation process describes how a JavaBean class is decorated with annotations to describe constraints.

Chapter 5, Validation APIs describes how to programmatically validate a JavaBean.

Chapter 6, Constraint metadata request APIs describes how the metadata query API works.

Chapter 7, Built-in Constraint definitions list all the built-in constraints.

Chapter 8, XML deployment descriptor describes the XML deployment descriptors for the configuration and the mapping.

Chapter 9, Exception model describes the exception model and hierarchy used by Bean Validation.

Chapter 10, Integration describes the different integration points of Bean Validation with other technologies. In some cases one has to refer to the to the respective specifications for the up-to-date integration rules.

In Appendix A, Terminology, key concepts are summarized. Some reviewers have found that reading the terminology section first helps to better understand the specification.

The changelog can be found at Appendix D, Changelog.

1.5. How to comment

The expert group is eager to receive feedback from readers. Feel free to contact us. You can get all the details at http://beanvalidation.org/contribute/.

Chapter 2. What's new in 1.1

Bean Validation 1.1 improves and build upon Bean Validation 1.0. The expert group and the community have been working on a few specific areas.

2.1. Openness

All of Bean Validation 1.1 work has been done in the open and in an open source way. Source code for the API, reference implementation, test compatibility kit as well as the specification and the website sources are available in the open. All discussions are done in the open in the publicly available development mailing list. Road map and proposals are also published on the website.

You can find all the details (mailing lists, source repositories etc.) at http://beanvalidation.org.

2.2. Dependency injection

Bean Validation uses a few components MessageInterpolator, TraversableResolver, ParameterNameProvider, ConstraintValidatorFactory and ConstraintValidator. Bean Validation 1.1 standardizes how these objects are managed by a container and how these objects can benefit from container services. In particular, CDI support within Java EE is being defined.

2.3. Method validation

Bean Validation 1.1 allows to put constraints to the parameters and return values of arbitrary methods and constructors. That way the Bean Validation API can be used to describe and validate the contract applying to a given method or constructor, that is:

  • the preconditions that must be met by the caller before the method or constructor may be invoked and

  • the postconditions that are guaranteed to the caller after a method or constructor invocation returns.

This enables a programming style known as "Programming by Contract" (PbC). Compared to traditional means of checking the sanity of argument and return values this approach has several advantages:

  • These checks are expressed declaratively and don't have to be performed manually, which results in less code to write, read and maintain.

  • The pre- and postconditions applying for a method or constructor don't have to be expressed again in the documentation, since any of its annotations will automatically be included in the generated JavaDoc. This reduces redundancies, thus avoiding efforts and inconsistencies between implementation and documentation.

2.4. Integration with Context and Dependency Injection

The integration points with Context and Dependency Injection (CDI) have been increased and reworked. This opens up for a more natural and standard integration both in Java EE and Java SE and encompass dependency injection, component lifecycle management and interception for method validation.

2.5. Group conversion

The specification offers a way to alter the targeted group when validation cascading in happening. This feature is particularly useful to reuse a given object (graph) and to avoid leaking groups between various object subgraphs. It also makes for more readable constraints.

2.6. Message interpolation via the unified expression language

Constraint violation messages can now use EL expressions for a much more flexible rendering and string formatting. In particular a formatter object is injected in the EL context to convert numbers dates etc. into the locale specific string representation. Likewise, the validated value is also available in the EL context.

2.7. Others

Many more minor changes have been done. Check out the change log for more details at Appendix D, Changelog.

Chapter 3. Constraint Definition

Constraints are defined by the combination of a constraint annotation and a list of constraint validation implementations. The constraint annotation is applied on types, fields, methods, constructors, parameters or other constraint annotations in case of composition.

Unless stated otherwise the default package name for the Bean Validation APIs is javax.validation.

3.1. Constraint annotation

A constraint on a JavaBean is expressed through one or more annotations. An annotation is considered a constraint definition if its retention policy contains RUNTIME and if the annotation itself is annotated with javax.validation.Constraint.

/**
 * Marks an annotation as being a Bean Validation constraint.
 * <p/>
 * A given constraint annotation must be annotated by a {@code @Constraint}
 * annotation which refers to its list of constraint validation implementations.
 * <p/>
 * Each constraint annotation must host the following attributes:
 * <ul>
 *     <li>{@code String message() default [...];} which should default to an error
 *     message key made of the fully-qualified class name of the constraint followed by
 *     {@code .message}. For example {@code "{com.acme.constraints.NotSafe.message}"}</li>
 *     <li>{@code Class<?>[] groups() default {};} for user to customize the targeted
 *     groups</li>
 *     <li>{@code Class<? extends Payload>[] payload() default {};} for
 *     extensibility purposes</li>
 * </ul>
 * <p/>
 * When building a constraint that is both generic and cross-parameter, the constraint
 * annotation must host the {@code validationAppliesTo()} property.
 * A constraint is generic if it targets the annotated element and is cross-parameter if
 * it targets the array of parameters of a method or constructor.
 * <pre>
 *     ConstraintTarget validationAppliesTo() default ConstraintTarget.IMPLICIT;
 * </pre>
 * This property allows the constraint user to choose whether the constraint
 * targets the return type of the executable or its array of parameters.
 *
 * A constraint is both generic and cross-parameter if
 * <ul>
 *     <li>two kinds of {@code ConstraintValidator}s are attached to the
 *     constraint, one targeting {@link ValidationTarget#ANNOTATED_ELEMENT}
 *     and one targeting {@link ValidationTarget#PARAMETERS},</li>
 *     <li>or if a {@code ConstraintValidator} targets both
 *     {@code ANNOTATED_ELEMENT} and {@code PARAMETERS}.</li>
 * </ul>
 *
 * Such dual constraints are rare. See {@link SupportedValidationTarget} for more info.
 * <p/>
 * Here is an example of constraint definition:
 * <pre>
 * &#64;Documented
 * &#64;Constraint(validatedBy = OrderNumberValidator.class)
 * &#64;Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
 * &#64;Retention(RUNTIME)
 * public &#64;interface OrderNumber {
 *     String message() default "{com.acme.constraint.OrderNumber.message}";
 *     Class<?>[] groups() default {};
 *     Class<? extends Payload>[] payload() default {};
 * }
 * </pre>
 *
 * @author Emmanuel Bernard
 * @author Gavin King
 * @author Hardy Ferentschik
 */
@Documented
@Target({ ANNOTATION_TYPE })
@Retention(RUNTIME)
public @interface Constraint {

    /**
     * {@link ConstraintValidator} classes must reference distinct target types
     * for a given {@link ValidationTarget}
     * If two {@code ConstraintValidator}s refer to the same type,
     * an exception will occur.
     * <p/>
     * At most one {@code ConstraintValidator} targeting the array of parameters of
     * methods or constructors (aka cross-parameter) is accepted. If two or more
     * are present, an exception will occur.
     *
     * @return array of (@code ConstraintValidator} classes implementing the constraint
     */
    Class<? extends ConstraintValidator<?, ?>>[] validatedBy();
}

A constraint is said to be generic if it has at least one constraint validator targeting the element annotated i.e. targeting the (returned) element annotated by the constraint (a bean, a field, a getter, a method/constructor return value or a method/constructor parameter). A constraint is said to be cross-parameter if it has one constraint validator targeting the array of parameters of a method or constructor (to validate the consistency of several method/constructor parameters). A Bean Validation constraint is most of the time either a generic constraint or a cross-parameter constraint. In rare situations, a constraint can be both.

Generic constraint annotations can target any of the following ElementTypes:

  • FIELD for constrained attributes

  • METHOD for constrained getters and constrained method return values

  • CONSTRUCTOR for constrained constructor return values

  • PARAMETER for constrained method and constructor parameters

  • TYPE for constrained beans

  • ANNOTATION_TYPE for constraints composing other constraints

Cross-parameter constraint annotations can target any of the following ElementTypes:

  • METHOD

  • CONSTRUCTOR

  • ANNOTATION_TYPE for cross-parameter constraints composing other cross-parameter constraints

A constraint annotation that is both can target the union of the generic and cross-parameter constraint annotations targets.

While other ElementTypes are not forbidden, the provider does not have to recognize and process constraints placed on such types.

Since a given constraint definition applies to one or more specific Java types, the JavaDoc for the constraint annotation should clearly state which types are supported. Applying a constraint annotation to an incompatible type will raise an UnexpectedTypeException. Care should be taken on defining the list of ConstraintValidators. The type resolution algorithm (see Section 4.6.4, “ConstraintValidator resolution algorithm”) could lead to exceptions if the ConstraintValidator list leads to ambiguities.

At most one ConstraintValidator supporting cross-parameter validation must be present for a given constraint. A ConstraintDefinitionException is raised otherwise. The JavaDoc should clearly state if the constraint is a generic and / or a cross-parameter constraint.

If a constraint definition is not valid, a ConstraintDefinitionException is raised either at validation time or when the metadata is requested. Invalid constraint definitions causes are multiple but include missing or illegal message or groups elements (see Section 3.1.1, “Constraint definition properties”).

Note

Bean Validation defines rules for applying constraint annotations in inheritance hierarchies, described in Section 4.3, “Inheritance (interface and superclass)” and Section 4.5.5, “Method constraints in inheritance hierarchies”. It is therefore not recommended to specify the meta annotation java.lang.annotation.Inherited at constraint annotation types, as it is not relevant in the context of Bean Validation and would conflict with the proposed rules.

3.1.1. Constraint definition properties

A constraint definition may have attributes that are specified at the time the constraint is applied to a JavaBean. The properties are mapped as annotation elements. The annotation element names message, groups, validationAppliesTo and payload are considered reserved names; annotation elements starting with valid are not allowed; a constraint may use any other element name for its attributes.

3.1.1.1. message

Every constraint annotation must define a message element of type String.

String message() default "{com.acme.constraint.MyConstraint.message}";

The message element value is used to create the error message. See Section 5.3, “Message interpolation” for a detailed explanation. It is recommended to default message values to resource bundle keys to enable internationalization. It is also recommended to use the following convention: the resource bundle key should be the fully qualified class name of the constraint annotation concatenated to .message as shown in the previous program listing.

Built-in Bean Validation constraints follow this convention.

3.1.1.2. groups

Every constraint annotation must define a groups element that specifies the processing groups with which the constraint declaration is associated. The type of the groups parameter is Class<?>[].

Class<?>[] groups() default {};

The default value must be an empty array.

If no group is specified when declaring the constraint on an element, the Default group is considered declared.

See Section 5.1.3, “groups” for more information.

Groups are typically used to control the order in which constraints are evaluated, or to perform validation of the partial state of a JavaBean.

3.1.1.3. payload

Constraint annotations must define a payload element that specifies the payload with which the constraint declaration is associated. The type of the payload parameter is Payload[].

Class<? extends Payload>[] payload() default {};

The default value must be an empty array.

Each attachable payload extends Payload.

/**
 * Payload type that can be attached to a given
 * constraint declaration.
 * <p/>
 * Payloads are typically used to carry on metadata information
 * consumed by a validation client.
 * </p>
 * Use of payloads is not considered portable.
 *
 * @author Emmanuel Bernard
 * @author Gerhard Petracek
 */
public interface Payload {
}

Payloads are typically used by validation clients to associate some metadata information with a given constraint declaration. Payloads are typically non-portable. Describing payloads as interface extensions as opposed to a string-based approach allows an easier and more type-safe approach.

One use case for payload shown in Example 3.1, “Use of payload to associate severity to a constraint” is to associate a severity to a constraint. This severity can be exploited by a presentation framework to adjust how a constraint failure is displayed.

Example 3.1. Use of payload to associate severity to a constraint

package com.acme.severity;

public class Severity {
    public static class Info implements Payload {};
    public static class Error implements Payload {};
}

public class Address {
    @NotNull(message="would be nice if we had one", payload=Severity.Info.class)
    public String getZipCode() { [...] }

    @NotNull(message="the city is mandatory", payload=Severity.Error.class) 
    String getCity() { [...] }
}

The payload information can be retrieved from error reports via the ConstraintDescriptor either accessed through the ConstraintViolation objects (see Section 5.2, “ConstraintViolation”) or through the metadata API (see Section 6.11, “ConstraintDescriptor”).

3.1.1.4. validationAppliesTo

validationAppliesTo is used at constraint declaration time to clarify what the constraint targets (i.e. the annotated element, the method return value or the method parameters).

The element validationAppliesTo must only be present for constraints that are both generic and cross-parameter, it is mandatory in this situation. A ConstraintDefinitionException is raised if these rules are violated.

The type of the validationAppliesTo parameter is ConstraintTarget. The default value must be ConstraintTarget.IMPLICIT.

Example 3.2. validationAppliesTo and ConstraintTarget

ConstraintTarget validationAppliesTo() default ConstraintTarget.IMPLICIT;
/**
 * Defines the constraint target.
 *
 * @author Emmanuel Bernard
 * @since 1.1
 */
public enum ConstraintTarget {

    /**
     * Discover the type when no ambiguity is present
     * <ul>
     *     <li>if neither on a method nor a constructor, it implies the annotated element
     *     (type, field etc),</li>
     *     <li>if on a method or constructor with no parameter, it implies
     *     {@code RETURN_VALUE},</li>
     *     <li>if on a method with no return value ({@code void}), it implies
     *     {@code PARAMETERS}.</li>
     * </ul>
     * Otherwise, {@code IMPLICIT} is not accepted and either {@code RETURN_VALUE} or
     * {@code PARAMETERS} is required. This is the case for constructors with parameters
     * and methods with parameters and return value.
     */
    IMPLICIT,

    /**
     * Constraint applies to the return value of a method or a constructor.
     */
    RETURN_VALUE,

    /**
     * Constraint applies to the parameters of a method or a constructor
     */
    PARAMETERS
}

If a ConstraintTarget is used in an illegal situation, a ConstraintDeclarationException is raised either at validation time or when the metadata is requested. Examples of illegal situations are:

  • using IMPLICIT in a situation that cannot be inferred (see the JavaDoc for the detailed rules),

  • using PARAMETERS on a constructor or method that has no parameter,

  • using RETURN_VALUE on a method with no return value,

  • using PARAMETERS or RETURN_VALUE on a type - class or interface - or on a field.

Constraint users are encouraged to explicitly set the ConstraintTarget target when using a constraint supporting both on a method or constructor as it improves readability.

3.1.1.5. Constraint specific parameter

The constraint annotation definitions may define additional elements to parameterize the constraint. For example, a constraint that validates the length of a string can use an annotation element named length to specify the maximum length at the time the constraint is declared.

3.1.2. Examples

Example 3.3. Simple constraint definition

//assuming OrderNumberValidator is a generic constraint validator

package com.acme.constraint;

/**
 * Mark a String as representing a well formed order number
 */
@Documented
@Constraint(validatedBy = OrderNumberValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface OrderNumber {
    String message() default "{com.acme.constraint.OrderNumber.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

Example 3.3, “Simple constraint definition” marks a String as a well-formed order number. The constraint validator is implemented by OrderNumberValidator.

Example 3.4. Simple cross-parameter constraint definition

//assuming DateParametersConsistentValidator is a cross-parameter
//constraint validator

package com.acme.constraint;

/**
 * Cross-parameter constraint ensuring that two date parameters
 * of a method are in the correct order.
 */
@Documented
@Constraint(validatedBy = DateParametersConsistentValidator.class)
@Target({ METHOD, CONSTRUCTOR, ANNOTATION_TYPE })
@Retention(RUNTIME)
public @interface DateParametersConsistent {
    String message() default "{com.acme.constraint.DateParametersConsistent.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

Example 3.4, “Simple cross-parameter constraint definition” shows a cross-parameter constraint which ensures that two date parameters of a method are in the correct order. The constraint validator is implemented by DateParametersConsistentValidator.

Example 3.5. Constraint that is both generic and cross parameter

//assuming ELAssertValidator is both a generic and cross-parameter
//constraint validator

package com.acme.constraint;

/**
 * EL expression to be validated.
 * This constraint accepts any type and can validate both the
 * annotated type or apply restrictions across parameters.
 */
@Documented
@Constraint(validatedBy=ELAssertValidator.class)
@Target({ METHOD, FIELD, TYPE, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface ELAssert {
    String message() default "{com.acme.constraint.DateParametersConsistent.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
    ConstraintTarget validationAppliesTo() default ConstraintTarget.IMPLICIT;

    String expression();
}
@ELAssert(
    message="Please check that your passwords match and try again.",
    expression="param[1]==param[2]", 
    validationAppliesTo=ConstraintType.PARAMETERS
)
public User createUser(String email, String password, String repeatPassword) { [...] }

Example 3.5, “Constraint that is both generic and cross parameter” shows a constraint that can be applied both on the annotated element and across parameters of a method or a constructor. Note in this case the presence of validationAppliesTo.

Example 3.6. Constraint definition with default parameter

package com.acme.constraint;

/**
 * A frequency in Hz as audible to human ear.
 * Adjustable to the age of the person.
 * Accept Numbers.
 */
@Documented
@Constraint(validatedBy = AudibleValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface Audible {
    Age age() default Age.YOUNG;
    String message() default "{com.acme.constraint.Audible.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    public enum Age {
        YOUNG,
        WONDERING
        OLD
    }
}

Example 3.6, “Constraint definition with default parameter” ensures that a given frequency is within the scope of human ears. The constraint definition includes an optional parameter that may be specified when the constraint is applied.

Example 3.7. Constraint definition with mandatory parameter

package com.acme.constraint;

/**
 * Defines the list of values accepted
 * Accepts int or Integer objects
 */
@Documented
@Constraint(validatedBy = DiscreteListOfIntegerValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface Acceptable {
    int[] value();
    String message() default "{com.acme.constraint.Acceptable.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

Example 3.7, “Constraint definition with mandatory parameter” defines a list of acceptable values expressed as an array: the value property must be specified when the constraint is applied.

3.2. Applying multiple constraints of the same type

It is often useful to declare the same constraint more than once to the same target, with different properties. A common example is the @Pattern constraint, which validates that its target matches a specified regular expression. Other constraints have this requirement as well. The same constraint type can belong to different groups and have specific error messages depending on the targeted group.

To support this requirement, the bean validation provider treats regular annotations (annotations not annotated by @Constraint) whose value element has a return type of an array of constraint annotations in a special way. Each element in the value array are processed by the Bean Validation implementation as regular constraint annotations. This means that each constraint specified in the value element is applied to the target. The annotation must have retention RUNTIME and can be applied on a type, field, property, executable parameter, executable return value, executable cross-parameter or another annotation. It is recommended to use the same set of targets as the initial constraint.

Note to constraint designers: each constraint annotation should be coupled with its corresponding multi-valued annotation. The specification recommends, though does not mandate, the definition of an inner annotation named List.

Example 3.8. Multi-valued constraint definition

/**
 * Validate a zipcode for a given country 
 * The only supported type is String
 */
@Documented
@Constraint(validatedBy = ZipCodeValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface ZipCode {

    String countryCode();

    String message() default "{com.acme.constraint.ZipCode.message}";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};

    /**
     * Defines several @ZipCode annotations on the same element
     * @see (@link ZipCode}
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        ZipCode[] value();
    }    
}

Example 3.9. Multi-valued constraint declaration

public class Address {
    @ZipCode.List( {
            @ZipCode(countryCode="fr", groups=Default.class
                     message = "zip code is not valid"),
            @ZipCode(countryCode="fr", groups=SuperUser.class
                     message = "zip code invalid. Requires overriding before saving.")
            } )
    private String zipcode;
}

In this example, both constraints apply to the zipcode field but with different groups and with different error messages.

Using two different multi-constraint annotations for the same underlying constraint type on the same target (i.e. class or property) is not considered portable and is discouraged.

3.3. Constraint composition

This specification allows you to compose constraints to create higher level constraints.

Constraint composition is useful in several ways:

  • Avoid duplication and facilitate reuse of more primitive constraints.

  • Expose primitive constraints as part of a composed constraint in the metadata API and enhance tool awareness.

Composition is done by annotating a constraint annotation with the composing constraint annotations.

Example 3.10. Composition is done by annotating the composed constraint

@Pattern(regexp="[0-9]*")
@Size(min=5, max=5)
@Constraint(validatedBy = FrenchZipcodeValidator.class)
@Documented
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface FrenchZipcode {
    String message() default "Wrong zipcode";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        FrenchZipcode[] value();
    }
}

Annotating an element with @FrenchZipcode (the composed annotation) is equivalent to annotating it with @Pattern(regexp="[0-9]*"), @Size(min=5, max=5) (the composing annotations) and @FrenchZipcode. More formally, each constraint annotation hosted on a constraint annotation is applied to the target element and this is done recursively. Note that the main annotation and its constraint validation implementation is also applied. By default, each failing constraint generates an error report. Groups from the main constraint annotation are inherited by the composing annotations. Any groups definition on a composing annotation is ignored. Payload from the main constraint annotation is inherited by the composing annotations. Any payload definition on a composing annotation is ignored. The constraint target from the main constraint annotation is inherited by the composing annotations. Any validationAppliesTo definition on a composing annotation is ignored.

The type upon which composed constraint is placed must be compatible with all constraints (composing and composed). A constraint designer should ensure that such a type exists and lists in the JavaDoc all the compatible types.

All composed and composing constraints must have a constraint type in common. In particular, it is not legal to mix a pure generic constraint and a pure cross-parameter constraint.

It is possible to ensure that composing annotations do not raise individual error reports. In this scenario, if one or more composing annotations are invalid, the main constraint is automatically considered invalid and the corresponding error report is generated. To mark a constraint as raising a single constraint error report if either the composed or one of the composing constraints fail, use the @ReportAsSingleViolation annotation.

Example 3.11. If any of the composing constraints fail, the error report corresponding to @FrenchZipcode is raised and none other.

@Pattern(regexp="[0-9]*")
@Size(min=5, max=5)
@ReportAsSingleViolation
@Constraint(validatedBy = FrenchZipcodeValidator.class)
@Documented
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface FrenchZipcode {
    String message() default "Wrong zipcode";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        FrenchZipcode[] value();
    }
}

The definition of @ReportAsSingleViolation is as follows.

/**
 * A constraint annotation hosting this annotation will return the
 * composed annotation error report if any of the composing annotations fail.
 * The error reports of each individual composing constraint are ignored.
 * <p/>
 * Note: Evaluation of composed constraints stops on the first validation
 * error in case the composing constraint is annotated with
 * {@code @ReportAsSingleViolation}.
 *
 * @author Emmanuel Bernard
 */
@Target({ ANNOTATION_TYPE })
@Retention(RUNTIME)
public @interface ReportAsSingleViolation {
}

More specifically, if a composed constraint is marked as @ReportAsSingleViolation, the evaluation of the composing constraints stops at the first failing constraint and the error report corresponding to the composed constraint is generated and returned.

Composing annotations can define the value of message and custom attributes (excluding groups, payload and validationAppliesTo) but these are fixed in the composed constraint definition.

Example 3.12. Composing annotations can use attributes. They are fixed for a given main annotation. All @FrenchZipcode constraints have a @Size restricted to 5.

@Pattern(regexp="[0-9]*")
@Size(min=5, max=5)
@Constraint(validatedBy = FrenchZipcodeValidator.class)
@Documented
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface FrenchZipcode {
    String message() default "Wrong zipcode";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        FrenchZipcode[] value();
    }
}

It is possible to override attributes and messages defined on a composing annotation. An attribute from the main annotation is used to override one or more attributes of the composing annotations. Such an attribute is annotated with the @OverridesAttribute annotation or its multivalued equivalent @OverridesAttribute.List.

Example 3.13. Attributes from composing annotations can be overridden by attributes from the composed annotation.

@Pattern(regexp="[0-9]*")
@Size
@Constraint(validatedBy = FrenchZipcodeValidator.class)
@Documented
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface FrenchZipcode {
    String message() default "Wrong zipcode";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    @OverridesAttribute.List( {
        @OverridesAttribute(constraint=Size.class, name="min"),
        @OverridesAttribute(constraint=Size.class, name="max") } )
    int size() default 5;

    @OverridesAttribute(constraint=Size.class, name="message")
    String sizeMessage() default "{com.acme.constraint.FrenchZipcode.zipcode.size}";

    @OverridesAttribute(constraint=Pattern.class, name="message")
    String numberMessage() default "{com.acme.constraint.FrenchZipcode.number.size}";

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        FrenchZipcode[] value();
    }
}

The value of the composed constraint attribute annotated with @OverridesAttribute (@FrenchZipcode.sizeMessage) is applied to the composing constraint attribute named after OverridesAttribute.name and hosted on the composing constraint of type OverridesAttribute.constraint (@Size.message). Similarly, @FrenchZipcode.numberMessage value is mapped to @Pattern.message.

If left undefined, the default value for @OverridesAttribute.name is the name of the composed constraint attribute hosting the @OverridesAttribute annotation.

The types of the overridden and overriding attributes must be identical.

Note

A composing constraint can itself be a composed constraint. In this case, attribute values are overridden recursively according to the described rules. Note however, that a forwarding rule (as defined by @OverridesAttribute) is only applied to the direct composing constraints.

Using Example 3.13, “Attributes from composing annotations can be overridden by attributes from the composed annotation.”,

@FrenchZipcode(size=9, sizeMessage="Zipcode should be of size {max}")

is equivalent to

@FrenchZipcode

if @FrenchZipcode is defined as

@Pattern(regexp="[0-9]*")
@Size(min=9, max=9, message="Zipcode should be of size {max}")
@Constraint(validatedBy = FrenchZipcodeValidator.class)
@Documented
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface FrenchZipcode {
    String message() default "Wrong zipcode";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        FrenchZipcode[] value();
    }
}

If a constraint is used more than once as a composing constraint, the multi value constraints model as described in Section 3.2, “Applying multiple constraints of the same type” is used. To select a specific composing constraint, OverridesAttribute.constraintIndex is used. It represents the constraint index in the value array. If index is undefined, the single constraint declaration is targeted.

Example 3.14. Use of constraintIndex in @OverridesAttribute

@Pattern.List( {
    @Pattern(regexp="[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}"), //email
    @Pattern(regexp=".*?emmanuel.*?") //emmanuel
} )
@Constraint(validatedBy={})
@Documented
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface EmmanuelsEmail {
    String message() default "Not emmanuel's email";

    @OverridesAttribute(constraint=Pattern.class, name="message", constraintIndex=0)
    String emailMessage() default "Not an email";

    @OverridesAttribute(constraint=Pattern.class, name="message", constraintIndex=1)
    String emmanuelMessage() default "Not Emmanuel";

    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        EmmanuelsEmail[] value();
    }
}

@OverridesAttribute definition is as follows:

/**
 * Marks an attribute as overriding the attribute of a composing constraint.
 * Both attributes must share the same type.
 *
 * @author Emmanuel Bernard
 */
@Retention(RUNTIME)
@Target({ METHOD })
public @interface OverridesAttribute {

    /**
     * @return constraint type the attribute is overriding
     */
    Class<? extends Annotation> constraint();

    /**
     * Name of the Constraint attribute overridden.
     * Defaults to the name of the attribute hosting {@code @OverridesAttribute}.
     *
     * @return name of constraint attribute overridden
     */
    String name();

    /**
     * The index of the targeted constraint declaration when using
     * multiple constraints of the same type.
     * <p/>
     * The index represents the index of the constraint in the
     * {@code value()} array.
     * <p/>
     * By default, no index is defined and the single constraint declaration
     * is targeted.
     *
     * @return constraint declaration index if multivalued annotation is used
     */
    int constraintIndex() default -1;

    /**
     * Defines several {@link OverridesAttribute} annotations on the same element
     *
     * @see javax.validation.OverridesAttribute
     */
    @Documented
    @Target({ METHOD })
    @Retention(RUNTIME)
    public @interface List {

        OverridesAttribute[] value();
    }
}

The following elements uniquely identify an overridden constraint attribute:

  • OverridesAttribute.constraint

  • OverridesAttribute.name

  • OverridesAttribute.constraintIndex

If the composition is invalid, e.g.

  • infinitely recursive composition

  • wrong attribute overriding

  • a single attribute mapped to more than one source attribute

  • a composing and composed constraint marked as different constraint types (i.e., generic and cross-parameter)

  • etc.

a ConstraintDefinitionException is raised either at validation time or when the metadata is requested.

Constraint designers are encouraged to make use of composition (recursively or not) based on the built-in constraints defined by the specification. The composing constraints are exposed through the Bean Validation metadata API (Section 6.11, “ConstraintDescriptor”). This metadata is particularly useful for third-party metadata consumers like persistence frameworks generating database schemas (such as Java Persistence) or presentation frameworks.

3.4. Constraint validation implementation

A constraint validation implementation performs the validation of a given constraint annotation for a given type. The implementation classes are specified by the validatedBy element of the @Constraint annotation that decorates the constraint definition. The constraint validation implementation implements the ConstraintValidator interface.

/**
 * Defines the logic to validate a given constraint {@code A}
 * for a given object type {@code T}.
 * <p/>
 * Implementations must comply to the following restriction:
 * <ul>
 *     <li>{@code T} must resolve to a non parameterized type</li>
 *     <li>or generic parameters of {@code T} must be unbounded
 *     wildcard types</li>
 * </ul>
 * <p/>
 * The annotation {@link SupportedValidationTarget} can be put on a
 * {@code ConstraintValidator} implementation to mark it as supporting
 * cross-parameter constraints. Check out {@link SupportedValidationTarget}
 * and {@link Constraint} for more information.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 */
public interface ConstraintValidator<A extends Annotation, T> {

    /**
     * Initializes the validator in preparation for
     * {@link #isValid(Object, ConstraintValidatorContext)} calls.
     * The constraint annotation for a given constraint declaration
     * is passed.
     * <p/>
     * This method is guaranteed to be called before any use of this instance for
     * validation.
     *
     * @param constraintAnnotation annotation instance for a given constraint declaration
     */
    void initialize(A constraintAnnotation);

    /**
     * Implements the validation logic.
     * The state of {@code value} must not be altered.
     * <p/>
     * This method can be accessed concurrently, thread-safety must be ensured
     * by the implementation.
     *
     * @param value object to validate
     * @param context context in which the constraint is evaluated
     *
     * @return {@code false} if {@code value} does not pass the constraint
     */
    boolean isValid(T value, ConstraintValidatorContext context);
}

Some restrictions apply on the generic type T (used in the isValid() method). T must

  • resolve to a non parameterized type (i.e. because the type is not using generics or because the raw type is used instead of the generic version)

  • or generic parameters of T must be unbounded wildcard types (i.e. <?>).

Note

This restriction is not a theoretical limitation and a future version of the specification might allow it.

By default, a ConstraintValidator targets the (returned) element annotated by the constraint. You can make a ConstraintValidator target the array of parameters of a method or constructor (aka cross-parameter) by annotating the validator implementation with @SupportedValidationTarget.

Example 3.15. @SupportedValidationTarget annotation and ValidationTarget enum

package javax.validation.constraintvalidation;

/**
 * Defines the target(s) a {@link ConstraintValidator} can validate.
 * <p/>
 * A {@code ConstraintValidator} can target the (returned) element
 * annotated by the constraint, the array of parameters of a method
 * or constructor (aka cross-parameter) or both.
 * <p/>
 * If {@code @SupportedValidationTarget} is not present, the
 * {@code ConstraintValidator} targets the (returned) element annotated
 * by the constraint.
 * <p/>
 * A {@code ConstraintValidator} targeting cross-parameter must accept
 * {@code Object[]} (or {@code Object}) as the type of object it validates.
 *
 * @author Emmanuel Bernard
 * @since 1.1
 */
@Documented
@Target({ TYPE })
@Retention(RUNTIME)
public @interface SupportedValidationTarget {

    ValidationTarget[] value();
}
package javax.validation.constraintvalidation;

/**
 * List of possible targets for a {@link ConstraintValidator}.
 *
 * @author Emmanuel Bernard
 * @since 1.1
 */
public enum ValidationTarget {

    /**
     * (Returned) element annotated by the constraint.
     */
    ANNOTATED_ELEMENT,

    /**
     * Array of parameters of the annotated method or constructor (aka cross-parameter).
     */
    PARAMETERS
}

A ConstraintValidator implementation can target both annotated elements and array of parameters.

If a ConstraintValidator targets array of parameters (cross-parameter), T must resolve to Object[] (or Object) in order to have the array of parameter values passed to the isValid() method. A ConstraintDefinitionException is raised otherwise.

Example 3.16. Example of cross parameter ConstraintValidator

@SupportedValidationTarget(ValidationTarget.PARAMETERS)
public class ScriptAssertValidator implements ConstraintValidator<ScriptAssert,Object[]> {
    @Override
    public void initialize(ScriptAssert constraintAnnotation) {
        [...]
    }

    @Override
    public boolean isValid(Object[] value, ConstraintValidatorContext context) {
        [...]
    }
}

Example 3.17, “Valid ConstraintValidator definitions” shows some examples of valid definitions.

Example 3.17. Valid ConstraintValidator definitions

//String is not making use of generics
public class SizeValidatorForString implements ConstraintValidator<Size, String> {
    [...]
}

//Collection uses generics but the raw type is used
public class SizeValidatorForCollection implements ConstraintValidator<Size, Collection> {
    [...]
}

//Collection uses generics and unbounded windcard type
public class SizeValidatorForCollection implements ConstraintValidator<Size, Collection<?>> {
    [...]
}

//Validator for cross-parameter constraint
@SupportedValidationTarget(ValidationTarget.PARAMETERS)
public class DateParametersConsistentValidator 
    implements ConstraintValidator<DateParametersConsistent, Object[]> {
    [...]
}

//Validator for both annotated elements and executable parameters
@SupportedValidationTarget({ValidationTarget.ANNOTATED_ELEMENT, ValidationTarget.PARAMETERS})
public class ELScriptValidator implements ConstraintValidator<ELScript, Object> {
    [...]
}

And some invalid definitions in Example 3.18, “Invalid ConstraintValidator definitions”.

Example 3.18. Invalid ConstraintValidator definitions

//parameterized type
public class SizeValidatorForString implements<Size, Collection<String>> {
    [...]
}

//parameterized type using bounded wildcard
public class SizeValidatorForCollection implements<Size, Collection<? extends Address>> {
    [...]
}

//cross-parameter validator accepting the wrong type
@SupportedValidationTarget(ValidationTarget.PARAMETERS)
public class NumberPositiveValidator implements ConstraintValidator<NumberPositive, Number> {
    [...]
}

The life cycle of a constraint validation implementation instance is undefined. Bean Validation providers are allowed to cache ConstraintValidator instances retrieved from the ConstraintValidatorFactory.

The initialize() method is called by the Bean validation provider prior to any use of the constraint implementation.

The isValid() method is evaluated by the Bean Validation provider each time a given value is validated. It returns false if the value is not valid, true otherwise. isValid() implementations must be thread-safe.

If the property is of an unanticipated type, an UnexpectedTypeException is raised. ConstraintValidator implementations raise this exception themselves if they receive an unsupported type. However, constraint designers are encouraged to make use of specialized ConstraintValidator implementations and delegate the type resolution to the Bean Validation provider (see the type matching algorithm described in Section 4.6.4, “ConstraintValidator resolution algorithm”).

If an exception occurs either in the initialize() or isValid() method, the runtime exception is wrapped into a ValidationException by the Bean Validation engine.

The constraint validation implementation is not allowed to change the state of the value passed to isValid().

Note

While not mandatory, it is considered a good practice to split the core constraint validation from the not null constraint validation (for example, an @Email constraint will return true on a null object, i.e. will not take care of the @NotNull validation).

null can have multiple meanings but is commonly used to express that a value does not make sense, is not available or is simply unknown. Those constraints on the value are orthogonal in most cases to other constraints. For example a String, if present, must be an email but can be null. Separating both concerns is a good practice.

The ConstraintValidatorContext object passed to the isValid() method carries information and operations available in the context the constraint is validated to.

/**
 * Provides contextual data and operation when applying a given constraint validator.
 *
 * At least one {@link ConstraintViolation} must be defined (either the default one,
 * of if the default {@code ConstraintViolation} is disabled, a custom one).
 *
 * @author Emmanuel Bernard
 */
public interface ConstraintValidatorContext {

    /**
     * Disables the default {@link ConstraintViolation} object generation (which
     * is using the message template declared on the constraint).
     * <p/>
     * Useful to set a different violation message or generate a {@code ConstraintViolation}
     * based on a different property.
     */
    void disableDefaultConstraintViolation();

    /**
     * @return the current un-interpolated default message
     */
    String getDefaultConstraintMessageTemplate();

    /**
     * Returns a constraint violation builder building a violation report
     * allowing to optionally associate it to a sub path.
     * The violation message will be interpolated.
     * <p/>
     * To create the {@link ConstraintViolation}, one must call either one of
     * the {@code addConstraintViolation()} methods available in one of the
     * interfaces of the fluent API.
     * If another method is called after {@code addConstraintViolation()} on
     * {@code ConstraintViolationBuilder} or any of its associated nested interfaces
     * an {@code IllegalStateException} is raised.
     * <p/>
     * If {@link ConstraintValidator#isValid(Object, ConstraintValidatorContext)} returns
     * {@code false}, a {@code ConstraintViolation} object will be built per constraint
     * violation report including the default one (unless
     * {@link #disableDefaultConstraintViolation()} has been called).
     * <p/>
     * {@code ConstraintViolation} objects generated from such a call
     * contain the same contextual information (root bean, path and so on) unless
     * the path has been overridden.
     * <p/>
     * To create a different {@code ConstraintViolation}, a new constraint violation builder
     * has to be retrieved from {@code ConstraintValidatorContext}
     *
     * Here are a few usage examples:
     * <pre>
     * //assuming the following domain model
     * public class User {
     *     public Map<String,Address> getAddresses() { ... }
     * }
     *
     * public class Address {
     *     public String getStreet() { ... }
     *     public Country getCountry() { ... }
     * }
     *
     * public class Country {
     *     public String getName() { ... }
     * }
     *
     * //From a property-level constraint on User.addresses
     * //Build a constraint violation on the default path - i.e. the "addresses" property
     * context.buildConstraintViolationWithTemplate( "this detail is wrong" )
     *             .addConstraintViolation();
     *
     * //From a class level constraint on Address
     * //Build a constraint violation on the default path + "street"
     * //i.e. the street property of Address
     * context.buildConstraintViolationWithTemplate( "this detail is wrong" )
     *             .addPropertyNode( "street" )
     *             .addConstraintViolation();
     *
     * //From a property-level constraint on  User.addresses
     * //Build a constraint violation on the default path + the bean stored
     * //under the "home" key in the map
     * context.buildConstraintViolationWithTemplate( "Incorrect home address" )
     *             .addBeanNode()
     *                 .inIterable().atKey( "home" )
     *             .addConstraintViolation();
     *
     * //From a class level constraint on User
     * //Build a constraint violation on the default path + addresses["home"].country.name
     * //i.e. property "country.name" on the object stored under "home" in the map
     * context.buildConstraintViolationWithTemplate( "this detail is wrong" )
     *             .addPropertyNode( "addresses" )
     *             .addPropertyNode( "country" )
     *                 .inIterable().atKey( "home" )
     *             .addPropertyNode( "name" )
     *             .addConstraintViolation();
     * </pre>
     * <p/>
     * Cross-parameter constraints on a method can create a node specific
     * to a particular parameter if required. Let's explore a few examples:
     * <p/>
     * <pre>
     * //Cross-parameter constraint on method createUser(String password, String passwordRepeat)
     * //Build a constraint violation on the default path + "passwordRepeat"
     * context.buildConstraintViolationWithTemplate("Passwords do not match")
     *             .addParameterNode(1)
     *             .addConstraintViolation();
     *
     * //Cross-parameter constraint on a method
     * //mergeAddresses(Map<String,Address> addresses, Map<String,Address> otherAddresses)
     * //Build a constraint violation on the default path + "otherAddresses["home"]
     * //i.e. the Address bean hosted in the "home" key of the "otherAddresses" map parameter
     * context.buildConstraintViolationWithTemplate(
     *         "Map entry home present in both and does not match")
     *             .addParameterNode(1)
     *             .addBeanNode()
     *                 .inIterable().atKey("home")
     *             .addConstraintViolation();
     *
     * //Cross-parameter constraint on a method
     * //mergeAddresses(Map<String,Address> addresses, Map<String,Address> otherAddresses)
     * //Build a constraint violation on the default path + "otherAddresses["home"].city
     * //i.e. on the "city" property of the Address bean hosted in
     * //the "home" key of the "otherAddresses" map
     * context.buildConstraintViolationWithTemplate(
     *         "Map entry home present in both but city does not match")
     *             .addParameterNode(1)
     *             .addPropertyNode("city")
     *                 .inIterable().atKey("home")
     *             .addConstraintViolation();
     * </pre>
     *
     * @param messageTemplate new un-interpolated constraint message
     * @return returns a constraint violation builder
     */
    ConstraintViolationBuilder buildConstraintViolationWithTemplate(String messageTemplate);

    /**
     * Returns an instance of the specified type allowing access to
     * provider-specific APIs. If the Bean Validation provider
     * implementation does not support the specified class,
     * {@link ValidationException} is thrown.
     *
     * @param type the class of the object to be returned
     * @return an instance of the specified class
     * @throws ValidationException if the provider does not support the call
     *
     * @since 1.1
     */
    <T> T unwrap(Class<T> type);

    /**
     * {@link ConstraintViolation} builder allowing to optionally associate
     * the violation report to a sub path.
     * <p/>
     * To create the {@code ConstraintViolation}, one must call either one of
     * the {@code addConstraintViolation()} methods available in one of the
     * interfaces of the fluent API.
     * <p/>
     * If another method is called after {@code addConstraintViolation()} on
     * {@code ConstraintViolationBuilder} or any of its associated objects
     * an {@code IllegalStateException} is raised.
     */
    interface ConstraintViolationBuilder {

        /**
         * Adds a node to the path the {@link ConstraintViolation} will be associated to.
         * <p/>
         * {@code name} describes a single property. In particular,
         * dot (.) is not allowed.
         *
         * @param name property name
         * @return a builder representing node {@code name}
         * @deprecated since 1.1 - replaced by {@link #addPropertyNode(String)},
         *             {@link #addBeanNode()} and {@link #addParameterNode(int)}
         */
        NodeBuilderDefinedContext addNode(String name);

        /**
         * Adds a property node to the path the {@link ConstraintViolation}
         * will be associated to.
         * <p/>
         * {@code name} describes a single property. In particular,
         * dot (.) is not allowed.
         *
         * @param name property name
         * @return a builder representing node {@code name}
         * @throws IllegalArgumentException if the name is null
         *
         * @since 1.1
         */
        NodeBuilderCustomizableContext addPropertyNode(String name);

        /**
         * Adds a bean node (class-level) to the path the {@link ConstraintViolation}
         * will be associated to.
         * Note that bean nodes are always leaf nodes.
         *
         * @return a builder representing the bean node
         *
         * @since 1.1
         */
        LeafNodeBuilderCustomizableContext addBeanNode();

        /**
         * Adds a method parameter node to the path the {@link ConstraintViolation}
         * will be associated to.
         * The parameter index must be valid (i.e. within the boundaries of the method
         * parameter indexes). May only be called from within cross-parameter validators.
         *
         * @param index the parameter index
         * @return a builder representing the index-th parameter node
         * @throws IllegalArgumentException if the index is not valid
         *
         * @since 1.1
         */
        NodeBuilderDefinedContext addParameterNode(int index);

        /**
         * Adds the new {@link ConstraintViolation} to be generated if the
         * constraint validator marks the value as invalid.
         * <p/>
         * Methods of this {@code ConstraintViolationBuilder} instance and its nested
         * objects throw {@code IllegalStateException} from now on.
         *
         * @return the {@code ConstraintValidatorContext} instance the
         *         {@code ConstraintViolationBuilder} comes from
         */
        ConstraintValidatorContext addConstraintViolation();

        /**
         * Represents a node whose context is known
         * (i.e. index, key and isInIterable)
         * and that is a leaf node (i.e. no subnode can be added).
         *
         * @since 1.1
         */
        interface LeafNodeBuilderDefinedContext {

            /**
             * Adds the new {@link ConstraintViolation} to be generated if the
             * constraint validator marks the value as invalid.
             * <p/>
             * Methods of the {@code ConstraintViolationBuilder} instance this object
             * comes from and the constraint violation builder nested
             * objects throw {@code IllegalStateException} after this call.
             *
             * @return {@code ConstraintValidatorContext} instance the
             *         {@code ConstraintViolationBuilder} comes from
             */
            ConstraintValidatorContext addConstraintViolation();
        }

        /**
         * Represents a node whose context is
         * configurable (i.e. index, key and isInIterable)
         * and that is a leaf node (i.e. no subnode can be added).
         *
         * @since 1.1
         */
        interface LeafNodeBuilderCustomizableContext {

            /**
             * Marks the node as being in an {@code Iterable} or a {@code Map}.
             * 
             * @return a builder representing iterable details
             */
            LeafNodeContextBuilder inIterable();

            /**
             * Adds the new {@link ConstraintViolation} to be generated if the
             * constraint validator mark the value as invalid.
             * <p/>
             * Methods of the {@code ConstraintViolationBuilder} instance this object
             * comes from and the constraint violation builder nested
             * objects throw {@code IllegalStateException} after this call.
             *
             * @return {@code ConstraintValidatorContext} instance the
             *         {@code ConstraintViolationBuilder} comes from
             */
            ConstraintValidatorContext addConstraintViolation();
        }

        /**
         * Represents refinement choices for a node which is
         * in an {@code Iterator} or {@code Map}.
         * <p/>
         * If the iterator is an indexed collection or a map,
         * the index or the key should be set.
         * <p/>
         * The node is a leaf node (i.e. no subnode can be added).
         *
         * @since 1.1
         */
        interface LeafNodeContextBuilder {

            /**
             * Defines the key the object is into the {@code Map}.
             *
             * @param key map key
             * @return a builder representing the current node
             */
            LeafNodeBuilderDefinedContext atKey(Object key);

            /**
             * Defines the index the object is into the {@code List} or array
             *
             * @param index index
             * @return a builder representing the current node
             */
            LeafNodeBuilderDefinedContext atIndex(Integer index);

            /**
             * Adds the new {@link ConstraintViolation} to be generated if the
             * constraint validator mark the value as invalid.
             * <p/>
             * Methods of the {@code ConstraintViolationBuilder} instance this object
             * comes from and the constraint violation builder nested
             * objects throw {@code IllegalStateException} after this call.
             *
             * @return {@code ConstraintValidatorContext} instance the
             *           {@code ConstraintViolationBuilder} comes from
             */
            ConstraintValidatorContext addConstraintViolation();
        }

        /**
         * Represents a node whose context is known
         * (i.e. index, key and isInIterable)
         * and that is not necessarily a leaf node (i.e. subnodes can
         * be added).
         */
        interface NodeBuilderDefinedContext {

            /**
             * Adds a node to the path the {@link ConstraintViolation} will be associated to.
             * <p/>
             * {@code name} describes a single property. In particular,
             * dot (.) is not allowed.
             *
             * @param name property name
             * @return a builder representing node {@code name}
             * @deprecated since 1.1 - replaced by {@link #addPropertyNode(String)}
             *             and {@link #addBeanNode()}
             */
            NodeBuilderCustomizableContext addNode(String name);

            /**
             * Adds a property node to the path the {@link ConstraintViolation}
             * will be associated to.
             * <p/>
             * {@code name} describes a single property. In particular,
             * dot (.) is not allowed.
             *
             * @param name property name
             * @return a builder representing node {@code name}
             * @throws IllegalArgumentException if the name is null
             *
             * @since 1.1
             */
            NodeBuilderCustomizableContext addPropertyNode(String name);

            /**
             * Adds a bean node (class-level) to the path the {@link ConstraintViolation}
             * will be associated to.
             * Note that bean nodes are always leaf nodes.
             *
             * @return a builder representing the bean node
             *
             * @since 1.1
             */
            LeafNodeBuilderCustomizableContext addBeanNode();

            /**
             * Adds the new {@link ConstraintViolation} to be generated if the
             * constraint validator marks the value as invalid.
             * <p/>
             * Methods of the {@code ConstraintViolationBuilder} instance this object
             * comes from and the constraint violation builder nested
             * objects throw {@code IllegalStateException} after this call.
             *
             * @return {@code ConstraintValidatorContext} instance the
             *           {@code ConstraintViolationBuilder} comes from
             */
            ConstraintValidatorContext addConstraintViolation();
        }

        /**
         * Represents a node whose context is
         * configurable (i.e. index, key and isInIterable)
         * and that is not necessarily a leaf node (i.e. subnodes can
         * be added).
         */
        interface NodeBuilderCustomizableContext {

            /**
             * Marks the node as being in an {@code Iterable} or a {@code Map}.
             *
             * @return a builder representing iterable details
             */
            NodeContextBuilder inIterable();

            /**
             * Adds a node to the path the {@link ConstraintViolation} will be associated to.
             *
             * {@code name} describes a single property. In particular,
             * dot (.) is not allowed.
             *
             * @param name property name
             * @return a builder representing node {@code name}
             * @deprecated since 1.1 - replaced by {@link #addPropertyNode(String)}
             *             and {@link #addBeanNode()}
             */
            NodeBuilderCustomizableContext addNode(String name);

            /**
             * Adds a property node to the path the {@link ConstraintViolation}
             * will be associated to.
             *
             * {@code name} describes a single property. In particular,
             * dot (.) is not allowed.
             *
             * @param name property name
             * @return a builder representing node {@code name}
             * @throws IllegalArgumentException if the name is null
             *
             * @since 1.1
             */
            NodeBuilderCustomizableContext addPropertyNode(String name);

            /**
             * Adds a bean node (class-level) to the path the {@link ConstraintViolation}
             * will be associated to.
             * Note that bean nodes are always leaf nodes.
             *
             * @return a builder representing the bean node
             *
             * @since 1.1
             */
            LeafNodeBuilderCustomizableContext addBeanNode();

            /**
             * Adds the new {@link ConstraintViolation} to be generated if the
             * constraint validator mark the value as invalid.
             * <p/>
             * Methods of the {@code ConstraintViolationBuilder} instance this object
             * comes from and the constraint violation builder nested
             * objects throw {@code IllegalStateException} after this call.
             *
             * @return {@code ConstraintValidatorContext} instance the
             *           {@code ConstraintViolationBuilder} comes from
             */
            ConstraintValidatorContext addConstraintViolation();
        }

        /**
         * Represents refinement choices for a node which is
         * in an {@code Iterator} or {@code Map}.
         * <p/>
         * If the iterator is an indexed collection or a map,
         * the index or the key should be set.
         * <p/>
         * The node is not necessarily a leaf node (i.e. subnodes can
          * be added).
         */
        interface NodeContextBuilder {
            
            /**
             * Defines the key the object is into the {@code Map}.
             *
             * @param key map key
             * @return a builder representing the current node
             */
            NodeBuilderDefinedContext atKey(Object key);

            /**
             * Defines the index the object is into the {@code List} or array.
             *
             * @param index index
             * @return a builder representing the current node
             */
            NodeBuilderDefinedContext atIndex(Integer index);

            /**
             * Adds a node to the path the {@code ConstraintViolation} will be associated to.
             *
             * {@code name} describes a single property. In particular,
             * dot (.) is not allowed.
             *
             * @param name property name
             * @return a builder representing node {@code name}
             * @deprecated since 1.1 - replaced by {@link #addPropertyNode(String)}
             *             and {@link #addBeanNode()}
             */
            NodeBuilderCustomizableContext addNode(String name);

            /**
             * Adds a property node to the path the {@link ConstraintViolation}
             * will be associated to.
             *
             * {@code name} describes a single property. In particular,
             * dot (.) is not allowed.
             *
             * @param name property name
             * @return a builder representing node {@code name}
             * @throws IllegalArgumentException if the name is null
             *
             * @since 1.1
             */
            NodeBuilderCustomizableContext addPropertyNode(String name);

            /**
             * Adds a bean node (class-level) to the path the {@link ConstraintViolation}
             * will be associated to.
             * <p/>
             * Note that bean nodes are always leaf nodes.
             *
             * @return a builder representing the bean node
             *
             * @since 1.1
             */
            LeafNodeBuilderCustomizableContext addBeanNode();

            /**
             * Adds the new {@link ConstraintViolation} to be generated if the
             * constraint validator mark the value as invalid.
             * <p/>
             * Methods of the {@code ConstraintViolationBuilder} instance this object
             * comes from and the constraint violation builder nested
             * objects throw {@code IllegalStateException} after this call.
             *
             * @return {@code ConstraintValidatorContext} instance the
             *         {@code ConstraintViolationBuilder} comes from
             */
            ConstraintValidatorContext addConstraintViolation();
        }
    }
}

The ConstraintValidatorContext interface allows redefinition of the default constraint message generated when a constraint is not valid. By default, each invalid constraint leads to the generation of one error object represented by a ConstraintViolation object. This object is built from the default constraint message template as defined by the constraint declaration and the context in which the constraint declaration is placed (bean, property, executable parameter, cross-parameter or executable return value).

The ConstraintValidatorContext methods let the constraint implementation disable the default ConstraintViolation generation and create one or more custom ones. The non-interpolated message passed as a parameter is used to build the ConstraintViolation message (the message interpolation operation is applied to it).

By default, the Path exposed on the ConstraintViolation represents the path to the bean, property, parameter, cross-parameter or return value hosting the constraint (see Section 5.2, “ConstraintViolation” for more information). You can point it to a subpath of this default path by using the constraint violation builder fluent API.

Example 3.19, “Using the fluent API to build custom constraint violations” shows a few examples.

Example 3.19. Using the fluent API to build custom constraint violations

//assuming the following domain model
public class User {
    public Map<String,Address> getAddresses() { [...] }
}

public class Address {
    public String getStreet() { [...] }
    public Country getCountry() { [...] }
}

public class Country {
   public String getName() { [...] }
}

//From a property-level constraint on User.addresses
//Build a constraint violation on the default path - i.e. the "addresses" property
context.buildConstraintViolationWithTemplate( "this detail is wrong" )
            .addConstraintViolation();

//From a class level constraint on Address
//Build a constraint violation on the default path + "street"
//i.e. the street property of Address
context.buildConstraintViolationWithTemplate( "this detail is wrong" )
            .addPropertyNode( "street" )
            .addConstraintViolation();

//From a property-level constraint on  User.addresses
//Build a constraint violation on the default path + the bean stored
//under the "home" key in the map
context.buildConstraintViolationWithTemplate( "Incorrect home address" )
            .addBeanNode()
                .inIterable().atKey( "home" )
            .addConstraintViolation();

//From a class level constraint on User
//Build a constraint violation on the default path + addresses["home"].country.name
//i.e. property "country.name" on the object stored under "home" in the map
context.buildConstraintViolationWithTemplate( "this detail is wrong" )
            .addPropertyNode( "addresses" )
            .addPropertyNode( "country" )
                .inIterable().atKey( "home" )
            .addPropertyNode( "name" )
            .addConstraintViolation();

//To create a subnode representing a method parameter from a cross-parameter constraint violation

//Cross-parameter constraint on method createUser(String password, String passwordRepeat)
//Build a constraint violation on the default path + "passwordRepeat"
context.buildConstraintViolationWithTemplate("Passwords do not match")
            .addParameterNode(1)
            .addConstraintViolation();

//Cross-parameter constraint on a method
//mergeAddresses(Map<String,Address> addresses, Map<String,Address> otherAddresses)
//Build a constraint violation on the default path + "otherAddresses["home"]
//i.e. the Address bean hosted in the "home" key of the "otherAddresses" map parameter
context.buildConstraintViolationWithTemplate(
        "Map entry home present in both and does not match" )
            .addParameterNode( 1 )
            .addBeanNode()
                .inIterable().atKey( "home" )
            .addConstraintViolation();

//Cross-parameter constraint on a method
//mergeAddresses(Map<String,Address> addresses, Map<String,Address> otherAddresses)
//Build a constraint violation on the default path + "otherAddresses["home"].city
//i.e. on the "city" property of the Address bean hosted in
//the "home" key of the "otherAddresses" map
context.buildConstraintViolationWithTemplate(
        "Map entry home present in both but city does not match" )
            .addParameterNode( 1 )
            .addPropertyNode( "city" )
                .inIterable().atKey( "home" )
            .addConstraintViolation();

If disableDefaultConstraintViolation() is called, no custom error is added (using the error builder) and if the constraint is not valid, a ValidationException is raised.

3.4.1. Examples

Example 3.20. ConstraintValidator implementation

/**
 * Check that a text is within the authorized syntax
 */
public class SyntaxValidator implements ConstraintValidator<Syntax, String> {
    private Set<Format> allowedFormats;

    /**
     * Configure the constraint validator based on the elements
     * specified at the time it was defined.
     * @param constraint the constraint definition
     */
    public void initialize(Syntax constraint) {
        allowedFormats = new HashSet( Arrays.asList( constraint.value() ) );
    }

    /**
     * Validate a specified value.
     * returns false if the specified value does not conform to the definition
     */
    public boolean isValid(String value, ConstraintValidatorContext context) {
        if ( value == null ) return true;

        return allowedFormats.size() == 0 
            || (! Collections.disjoint( guessFormat(value), allowedFormats ) );
    }

    Set<Format> guessFormats(String text) { [...] }
}

This ConstraintValidator checks that a text is within the accepted syntax. It also demonstrates an interesting best practice: return true on a null parameter.

The following listing shows a validator implementing the validation logic for a cross-parameter constraint.

Example 3.21. Cross-parameter validator implementation

/**
 * Check that two date parameters of a method are in the expected order. Expects the
 * 2nd and 3rd parameter of the validated method to be of type java.util.Date.
 */
@SupportedValidationTarget(ValidationTarget.PARAMETERS)
public class DateParametersConsistentValidator implements<DateParametersConsistent, Object[]> {

    /**
     * Configure the constraint validator based on the elements
     * specified at the time it was defined.
     * @param constraint the constraint definition
     */
    public void initialize(DateParametersConsistent constraint) {
    }

    /**
     * Validate a specified value.
     * returns false if the specified value does not conform to the definition
     */
    public boolean isValid(Object[] value, ConstraintValidatorContext context) {
        if ( value.length != 3 ) {
            throw new IllegalStateException( "Unexpected method signature" );
        }
        // one or both limits are unbounded => always consistent
        if ( value[1] == null || value[2] == null ) return true;
        return ( (Date) value[1] ).before( (Date) value[2] );
    }
}

The following listing shows a validator implementing the validation logic for a constraint that is both generic and cross-parameter.

Example 3.22. Generic and cross-parameter validator implementation

/**
 * Checks that an object passes the Expression Language expression
 * provided by the constraint.
 */
@SupportedValidationTarget({ValidationTarget.ANNOTATED_ELEMENT, ValidationTarget.PARAMETERS})
public class ELScriptValidator implements<ELScript, Object> {

    public void initialize(ELScript constraint) {
        [...]
    }

    public boolean isValid(Object value, ConstraintValidatorContext context) {
        [...]
    }
}

The next example shows how to use ConstraintValidatorContext.

Example 3.23. Use of ConstraintValidatorContext

/**
 * Check that a text is within the authorized syntax
 * Error messages are using either key:
 *  - com.acme.constraint.Syntax.unknown if no particular syntax is detected
 *  - com.acme.constraint.Syntax.unauthorized if the syntax is not allowed
 */
public class FineGrainedSyntaxValidator implements ConstraintValidator<Syntax, String> {
    private Set<Format> allowedFormats;

    /**
     * Configure the constraint validator based on the elements
     * specified at the time it was defined.
     * @param constraint the constraint definition
     */
    public void initialize(Syntax constraint) {
        allowedFormats = new HashSet( Arrays.asList( constraint.value() ) );
    }

    /**
     * Validate a specified value.
     * returns false if the specified value does not conform to the definition
     */
    public boolean isValid(String value, ConstraintValidatorContext context) {
        if ( value == null ) return true;
        Set<Format> guessedFormats = guessFormats(value);

        context.disableDefaultConstraintViolation();
        if ( guessedFormats.size() == 0 ) {
            String unknown = "{com.acme.constraint.Syntax.unknown}";
            context.buildConstraintViolationWithTemplate(unknown)
                       .addConstraintViolation();
            return false;
        }
        if ( allowedFormats.size() != 0 
            && Collections.disjoint( guessedFormats, allowedFormats ) ) {

            String unauthorized = "{com.acme.constraint.Syntax.unauthorized}";
            context.buildConstraintViolationWithTemplate(unauthorized)
                       .addConstraintViolation();
            return false;
        }
        return true;
    }

    Set<Format> guessFormats(String text) { [...] }
}

The default error message is disabled and replaced by a specific error message depending on the type of constraint violation detected. In this case, only one error report is returned at a given time but a constraint validation implementation can return several error reports.

3.5. The ConstraintValidatorFactory

Constraint validation implementation instances are created by a ConstraintValidatorFactory.

The life cycle of ConstraintValidator instances is fully dependent of the Bean Validation provider and piloted by the ConstraintValidatorFactory methods. Therefore, ConstraintValidatorFactory implementations (such as dependency injection frameworks) must consider these instances as belonging to a dependent scope. Bean Validation providers must release each instance retrieved. The ConstraintValidatorFactory instance that has created a ConstraintValidator instance must be the one that releases it. In other words, passing an instance of ConstraintValidator to a ConstraintValidatorFactory that has not created it is an error.

Note

ConstraintValidator instances created by the ValidatorFactory-level ConstraintValidatorFactory can be released when the ValidatorFactory is being closed.

Example 3.24. ConstraintValidatorFactory interface

/**
 * Instantiates a {@link ConstraintValidator} instance based off its class.
 * The {@code ConstraintValidatorFactory} is <b>not</b> responsible
 * for calling {@link ConstraintValidator#initialize(java.lang.annotation.Annotation)}.
 *
 * @author Dhanji R. Prasanna
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 */
public interface ConstraintValidatorFactory {

    /**
     * @param key The class of the constraint validator to instantiate
     *
     * @return A new constraint validator instance of the specified class
     */
    <T extends ConstraintValidator<?, ?>> T getInstance(Class<T> key);

    /**
     * Signals {@code ConstraintValidatorFactory} that the instance is no longer
     * being used by the Bean Validation provider.
     *
     * @param instance validator being released
     *
     * @since 1.1
     */
    void releaseInstance(ConstraintValidator<?, ?> instance);
}

The default ConstraintValidatorFactory provided by the Bean Validation provider implementation uses the public no-arg constructor of the ConstraintValidator class. A custom ConstraintValidatorFactory can be provided; for example it may benefit from dependency injection control in constraint implementations (see Section 5.5.7, “Bootstrapping considerations”). Any constraint implementation relying on ConstraintValidatorFactory behaviors specific to an implementation (dependency injection, no no-arg constructor and so on) are not portable, hence great care should be given before walking that path. Make sure to configure the Bean Validation provider to honor any specific needs your ConstraintValidator has. As constraint designer and writer, make sure to document any specific non compliant requirements.

ConstraintValidatorFactory should not cache instances as the state of each instance can be altered in the initialize() method.

If an exception occurs in the factory while retrieving the ConstraintValidator instance, the runtime exception is wrapped in a ValidationException. If the instance returned by the factory is null, a ValidationException is raised.

Chapter 4. Constraint declaration and validation process

The Bean Validation specification defines a framework for declaring constraints on JavaBean classes, fields and properties. Constraints are declared on types and evaluated against instances or graphs of instances.

Bean Validation also offers a way to declare constructor and method constraints where parameters and return values are the constrained elements. We will discuss method constraints declaration in detail in Section 4.5, “Method and constructor constraints”.

4.1. Requirements on classes to be validated

Objects hosting constraints and expecting to be validated by Bean Validation providers must fulfill the following requirements:

  • Properties to be validated must follow the method signature conventions for JavaBeans read properties, as defined by the JavaBeans specification. These properties are commonly referred as getters.

  • Static fields and static methods are excluded from validation.

  • Constraints can be applied to interfaces and superclasses.

What is a getter?

The JavaBeans specification specifies that a getter is a method whose

  • name starts with get and has a return type but no parameter

  • name starts with is, has no parameter and is returning boolean

The target of an annotation definition can be a field, property, type, constructor or method return value, constructor or method parameter or constructor or method cross-parameter provided that:

  • the constraint definition supports the specified target (java.lang.annotation.Target)

  • one of the ConstraintValidators declared on the constraint supports the declared type of the target or in the case of cross-parameter, one cross-parameter ConstraintValidator is present (see Section 4.6.4, “ConstraintValidator resolution algorithm” to learn about ConstraintValidator resolution).

4.1.1. Object validation

Constraint declarations can be applied to a class or an interface. Applying a constraint to a class or interface expresses a validation over the state of the class or the class implementing the interface.

4.1.2. Field and property validation

Constraint declarations can be applied on both fields and properties for the same object type. The same constraint should however not be duplicated between a field and its associated property (the constraint validation would be applied twice). It is recommended for objects holding constraint declarations to adhere to a single state access strategy (either annotated fields or properties).

Java Persistence and Bean Validation

For maximum portability, persistent properties hosting Bean Validation constraints should use the same access strategy used in Java Persistence. In other words, place your Bean Validation constraint annotations on the same element (field or getter) as your Java Persistence annotations.

When a field is annotated with a constraint declaration, field access strategy is used to access the state validated by such constraint.

When a property is annotated with a constraint declaration, property access strategy is used to access the state validated by such constraint.

When using field access strategy, the bean validation provider accesses the instance variable directly. When using the property access strategy, the bean validation provider accesses the state via the property accessor method. It is required that the class follows the method signature conventions for JavaBeans read properties (as defined by the JavaBeans Introspector class) for constrained properties when constrained properties are used. In this case, for every constraint property of type T, there is a getter method named get<Property-name>. The method must have no parameters. For boolean properties, is<Property-name> is an alternative name for the getter method. Specifically, if getX is the name of the getter method, where X is a string, the name of the persistent property is defined by the result of java.beans.Introspector.decapitalize(X).

The fields or methods visibility are not constrained.

4.1.3. Graph validation

In addition to supporting instance validation, validation of graphs of object is also supported. The result of a graph validation is returned as a unified set of constraint violations. @Valid is used to express validation traversal of an association.

Example 4.1. @Valid annotation

/**
 * Marks a property, method parameter or method return type for validation cascading.
 * <p/>
 * Constraints defined on the object and its properties are be validated when the
 * property, method parameter or method return type is validated.
 * <p/>
 * This behavior is applied recursively.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 */
@Target({ METHOD, FIELD, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface Valid {
}

Consider the situation where bean X contains a field of type Y. By annotating field Y with the @Valid annotation, the Validator will validate Y (and its properties) when X is validated. The exact type Z of the value contained in the field declared of type Y (subclass, implementation) is determined at runtime. The constraint definitions of Z are used. This ensures proper polymorphic behavior for associations marked @Valid.

Collection-valued, array-valued and generally Iterable fields and properties may also be decorated with the @Valid annotation. This causes the contents of the iterator to be validated. Any object implementing java.lang.Iterable is supported. This includes specifically:

  • arrays of objects

  • java.util.Collection

  • java.util.Set

  • java.util.List

  • java.util.Map (special treatment see below)

Each object provided by the iterator is validated. For Map, the value (retrieved by getValue) of each Map.Entry is validated (the key is not validated).

Like regular references, its type is determined at runtime and the constraint definitions for this particular type are used.

The @Valid annotation is applied recursively. A conforming implementation avoids infinite loops according to the rules described in Section 4.6.1, “Object graph validation”.

4.2. Constraint declaration

Constraint declarations are placed on classes or interfaces primarily through annotations. A constraint annotation (see Section 3.1, “Constraint annotation”), can be applied to a type, on any of the type's fields or on any of the JavaBeans-compliant properties.

When a constraint is defined on a class, the class instance being validated is passed to the ConstraintValidator. When a constraint is defined on a field, the value of the field is passed to the ConstraintValidator. When a constraint is defined on a getter, the result of the getter invocation is passed to the ConstraintValidator.

Section 4.5, “Method and constructor constraints” discusses in detail constraints on methods and constructors.

4.3. Inheritance (interface and superclass)

A constraint declaration can be placed on an interface. For a given class, constraint declarations held on superclasses as well as interfaces are evaluated by the Bean Validation provider. Rules are formally described in Section 4.4.6, “Formal group definitions”.

The effect of constraint declarations is cumulative. Constraints declared on a superclass getter will be validated along with any constraints defined on an overridden version of the getter according to the Java Language Specification visibility rules.

4.4. Group and group sequence

A group defines a subset of constraints. Instead of validating all constraints for a given object graph, only a subset is validated. This subset is defined by the group or groups targeted. Each constraint declaration defines the list of groups it belongs to. If no group is explicitly declared, a constraint belongs to the Default group.

Groups are represented by interfaces.

Example 4.2. Definition of groups

/**
 * Validation group verifing that a user is billable
 */
public interface Billable {}

/**
 * Customer can buy without any harrassing checking process
 */
public interface BuyInOneClick {
}

A constraint can belong to one or more groups.

Example 4.3. Assign groups to constraints

/**
 * User representation
 */
public class User {
    @NotNull
    private String firstname;

    @NotNull(groups = Default.class)
    private String lastname;

    @NotNull(groups = {Billable.class, BuyInOneClick.class})
    private CreditCard defaultCreditCard;
}

During the validation call, one or more groups are validated. All the constraints belonging to this set of group is evaluated on the object graph. In Example 4.3, “Assign groups to constraints”, @NotNull is checked on defaultCreditCard when either the Billable or BuyInOneClick group is validated. @NotNull on firstname and lastname are validated when the Default group is validated. Reminder: constraints held on superclasses and interfaces are considered.

Default is a group predefined by the specification

package javax.validation.groups;

/**
 * Default Bean Validation group.
 * <p/>
 * Unless a list of groups is explicitly defined:
 * <ul>
 *     <li>constraints belong to the {@code Default} group</li>
 *     <li>validation applies to the {@code Default} group</li>
 * </ul>
 * Most structural constraints should belong to the default group.
 *
 * @author Emmanuel Bernard
 */
public interface Default {
}

4.4.1. Group inheritance

In some situations, a group is a superset of one or more groups. This can be described by Bean Validation. A group may inherit one or more groups by using interface inheritance.

Example 4.4. Groups can inherit other groups

/**
 * Customer can buy without harrassing checking process
 */
public interface BuyInOneClick extends Default, Billable {}

For a given interface Z, constraints marked as belonging to the group Z (i.e. where the annotation element groups contains the interface Z) or any of the super interfaces of Z (inherited groups) are considered part of the group Z.

In the following example:

Example 4.5. Use of a inherited group

/**
 * User representation
 */
public class User {
    @NotNull
    private String firstname;

    @NotNull(groups = Default.class)
    private String lastname;

    @NotNull(groups = Billable.class)
    private CreditCard defaultCreditCard;
}

validating the group BuyInOneClick will lead to the following constraints checking:

  • @NotNull on firstname and lastname

  • @NotNull on defaultCreditCard

because Default and Billable are superinterfaces of BuyInOneClick.

4.4.2. Group sequence

By default, constraints are evaluated in no particular order regardless of which groups they belong to. It is however useful in some situations to control the order of constraints evaluation. There are often scenarios where a preliminary set of constraints should be evaluated prior to other constraints. Here are two examples:

  • The second group depends on a stable state to run properly. This stable state is verified by the first group.

  • The second group is a heavy consumer of time, CPU or memory and its evaluation should be avoided if possible.

To implement such ordering, a group can be defined as a sequence of other groups. Each group in a group sequence must be processed sequentially in the order defined by @GroupSequence.value when the group defined as a sequence is requested. Note that a group member of a sequence can itself be composed of several groups via inheritance or sequence definition. In this case, each composed group must respect the sequence order as well.

Processing a group is defined in Section 4.6, “Validation routine” ; if one of the groups processed in the sequence generates one or more constraint violations, the groups following in the sequence must not be processed. This ensures that a set of constraint is evaluated only if another set of constraint is valid.

Groups defining a sequence and groups composing a sequence must not be involved in a cyclic dependency:

  • either directly or indirectly

  • either through cascaded sequence definitions or group inheritance

If a group containing such a circularity is evaluated, a GroupDefinitionException is raised.

Groups defining a sequence should not directly inherit other groups. In other words, the interface hosting the group sequence should not have any super interface.

Groups defining a sequence should not be used directly in constraint declarations. In other words, the interface hosting the group sequence should not be used in a constraint declaration.

To define a group as a sequence, the interface must be annotated with the @GroupSequence annotation.

/**
 * Defines group sequence.
 * <p/>
 * The interface hosting {@code @GroupSequence} is representing
 * the group sequence.
 * When hosted on a class, represents the {@link Default} group
 * for that class.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 */
@Target({ TYPE })
@Retention(RUNTIME)
public @interface GroupSequence {

    Class<?>[] value();
}

Here is a usage example:

Example 4.6. Make use of group sequence

@ZipCodeCoherenceChecker(groups = Address.HighLevelCoherence.class)
public class Address {
    @NotNull @Size(max = 50)
    private String street1;

    @NotNull @ZipCode
    private String zipcode;

    @NotNull @Size(max = 30)
    private String city;

    /**
     * check coherence on the overall object
     * Needs basic checking to be green first
     */
    public interface HighLevelCoherence {}

    /**
     * check both basic constraints and high level ones.
     * high level constraints are not checked if basic constraints fail
     */
    @GroupSequence({Default.class, HighLevelCoherence.class})
    public interface Complete {}
}

In Example 4.6, “Make use of group sequence”, when the Address.Complete group is validated, all constraints belonging to the Default group are validated. If any of them fail, the validation skips the HighLevelCoherence group. If all Default constraints pass, HighLevelCoherence constraints are evaluated.

Note

A given constraint can belong to two or more groups ordered by a sequence. In this case, the constraint is evaluated as part of the first group and ignored in the subsequent group(s). See Section 4.6, “Validation routine” for more information.

4.4.3. Redefining the Default group for a class

In Example 4.6, “Make use of group sequence”, validating the Default group does not validate HighLevelCoherence constraints. To ensure a complete validation, a user must use the Complete group. This breaks some of the encapsulation you could expect. You can work around this by redefining what the Default group means for a given class. To redefine Default for a class, place a @GroupSequence annotation on the class; this sequence expresses the sequence of groups that does substitute Default for this class.

Example 4.7. Redefining Default group for Address

@GroupSequence({Address.class, HighLevelCoherence.class})
@ZipCodeCoherenceChecker(groups = Address.HighLevelCoherence.class)
public class Address {
    @NotNull @Size(max = 50)
    private String street1;

    @NotNull @ZipCode
    private String zipcode;

    @NotNull @Size(max = 30)
    private String city;

    /**
     * check coherence on the overall object
     * Needs basic checking to be green first
     */
    public interface HighLevelCoherence {}
}

In Example 4.7, “Redefining Default group for Address”, when an address object is validated for the group Default, all constraints belonging to the group Default and hosted on Address are evaluated. If none fails, all HighLevelCoherence constraints present on Address are evaluated. In other words, when validating the Default group for Address, the group sequence defined on the Address class is used.

Since sequences cannot have circular dependencies, using Default in the declaration of a sequence is not an option. Constraints hosted on a class A and belonging to the Default group (by default or explicitly) implicitly belong to the group A.

A sequence defined on a class A (i.e. redefining the Default groups for the class) must contain the group A. In other words, the default constraints hosted on a class must be part of the sequence definition. If a @GroupSequence redefining the Default group for a class A does not contain the group A, a GroupDefinitionException is raised when the class is validated or when its metadata is requested.

4.4.4. Implicit grouping

It is possible to implicitly group several constraints in the same group without explicitly listing such a group in the constraint declaration. Every constraint hosted on an interface Z and part of the Default group (implicitly or explicitly) belongs to the group Z. This is useful to validate the partial state of an object based on a role represented by an interface.

Example 4.8. Example of interface / group hosting constraints

/**
 * Auditable object contract
 */
public interface Auditable {
    @NotNull String getCreationDate();
    @NotNull String getLastUpdate();
    @NotNull String getLastModifier();
    @NotNull String getLastReader();
}

/**
 * Represents an order in the system
 */
public class Order implements Auditable {
    private String creationDate;
    private String lastUpdate;
    private String lastModifier;
    private String lastReader;

    private String orderNumber;

    public String getCreationDate() {
        return this.creationDate;
    }

    public String getLastUpdate() {
        return this.lastUpdate;
    }

    public String getLastModifier() {
        return this.lastModifier;
    }

    public String getLastReader() {
        return this.lastReader;
    }

    @NotNull @Size(min=10, max=10)
    public String getOrderNumber() {
        return this.orderNumber;
    }
}

When an Order object is validated on the Default group, the following constraints are validated: @NotNull on getCreationDate, getLastUpdate, getLastModifier, getLastReader, getOrderNumber and @Size on getOrderNumber as all belong to the Default group.

When an Order object is validated on the Auditable group, the following constraints are validated: @NotNull on getCreationDate, getLastUpdate, getLastModifier, getLastReader. Only the constraints present on Auditable (and any of its super interfaces) and belonging to the Default group are validated when the group Auditable is requested. It allows the caller to validate that a given object can be safely audited even if the object state itself is not valid.

4.4.5. Group conversion

When performing cascading validation, it is possible to use a different group than the one originally requested using the group conversion feature. Group conversions are declared by using the @ConvertGroup annotation.

Example 4.9. @ConvertGroup annotation

package javax.validation.groups;

/**
 * Converts group {@code from} to group {@code to} during cascading.
 * <p/>
 * Can be used everywhere {@link Valid} is used and must be on an element
 * annotated with {@code Valid}.
 *
 * @author Emmanuel Bernard
 * @since 1.1
 */
@Target({ TYPE, METHOD, FIELD, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
public @interface ConvertGroup {

    Class<?> from();

    Class<?> to();

    /**
     * Defines several {@link ConvertGroup} annotations
     * on the same element.
     */
    @Target({ TYPE, METHOD, FIELD, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    public @interface List {

        ConvertGroup[] value();
    }
}

@ConvertGroup and @ConvertGroup.List can be used everywhere @Valid can be used (associations, method/constructor parameters and return value). If these annotations are used without @Valid, a ConstraintDeclarationException is raised.

When an element is annotated with @Valid, validation is propagated. Groups are passed as is to the nested elements unless the @ConvertGroup annotation is used.

If the group expected to be passed to the nested element validation is defined as the from attribute of a @ConvertGroup annotation, the group used to effectively validate the nested element is the corresponding group defined in the to attribute.

Rules are not executed recursively. If a rule is found matching, subsequent rules are no longer evaluated. In particular, if a set of @ConvertGroup declaration chains group A to B and B to C, the group A will be converted to B and not to C. This both makes rules clearer and let you switch two groups.

It is not legal to have more than one conversion rule containing the same from value. In this case, a ConstraintDeclarationException is raised.

Like regular constraint declarations, the from attribute cannot refer to a group sequence. A ConstraintDeclarationException is raised in this situation. The to attribute can. The group sequence will then be expanded before validating the associated object.

Note

When validation is done, group sequences are expanded before validating the object and its cascaded objects with the expected groups. Group conversion on an associated object happens on the already expanded groups.

The group referred to in @ConvertGroup.from works on expanded groups (i.e., after the group sequence has been expanded), not necessarily groups passed to the various validate methods.

The group referred to in @ConvertGroup.to will be expanded before validating the cascaded object just like a call to the various validate method would have done.

Note

Like most Bean Validation error cases, an illegal set of rules can be discovered statically (at compile time). For example, an annotation processor could detect such errors.

Note

Group circularity in a group conversion are not problematic because:

  • only one rule is applied for a given cascade (rules are not applied recursively)

  • validation cascading is stopped when the same instance / property is validated with the same group in a given path (existing rule)

@ConvertGroup and @ConvertGroup.List can only be placed where @Valid is present to ensure proper respect of the Liskov substitution principle: if rules were to be defined on an overriding method of a method marked as cascading validation, the rules could end up altering the list of constraints validated by the super type and thus violating the Liskov substitution principle.

Likewise, if a sub type overrides/implements a method originally defined in several parallel types of the hierarchy (e.g. two interfaces not extending each other, or a class and an interface not implemented by said class) and if that method's return value has been marked for cascading validation in one of the parallel types, no group conversion rule may be declared for that method's return value in the parallel types of the hierarchy. This again is to avoid an unexpected altering of the post conditions to be guaranteed to the caller.

If any of these rules is violated, a ConstraintDeclarationException is raised by default as defined in Section 4.5.5, “Method constraints in inheritance hierarchies”.

Group conversion is quite useful to facilitate object graph reuse without spreading the validation group definitions across several layers. Let's look at an example.

4.4.5.1. Group conversion examples

In this example we will reuse the Address group split and match it to the User group split.

Example 4.10. Example of group conversion

public interface Complete extends Default {}
public interface BasicPostal {}
public interface FullPostal extends BasicPostal {}

public class Address {
    @NotNull(groups=BasicPostal.class)
    String street1;

    String street2;

    @ZipCode(groups=BasicPostal.class)
    String zipCode;

    @CodeChecker(groups=FullPostal.class)
    String doorCode;
}

public class User {
    @Valid
    @ConvertGroup.List( {
        @ConvertGroup(from=Default.class, to=BasicPostal.class),
        @ConvertGroup(from=Complete.class, to=FullPostal.class)
    } )
    Set<Address> getAddresses() { [...] }
}

When validating an instance of User with the Default group, the associated addresses are validated with the BasicPostal group. When validating an instance of User with the Complete group, the associated addresses are validated with the FullPostal group.

The following example shows an illegal declaration of a group conversion rule on a method's return value:

Example 4.11. Example of an illegal group conversion

public interface BasicPostal {}

public class Order { [...] }

public interface RetailOrderService {

    @Valid
    Order placeOrder(String itemNo, int quantity);
}

public interface B2BOrderService {

    @Valid
    @ConvertGroup(from=Default.class, to=BasicPostal.class)
    Order placeOrder(String itemNo, int quantity);
}

public class OrderService implements RetailOrderService, B2BOrderService {

    @Override
    public Order placeOrder(String itemNo, int quantity) {
        [...]
    }
}

Here the class OrderService implements the two unrelated interfaces RetailOrderService and B2BOrderService, which both define a method placeOrder(), marking the return value as cascaded.

The group conversion declared in B2BOrderService is illegal as per the rules defined in the previous section, since the set of applied validation groups might be altered unexpectedly for a client of the RetailOrderService interface.

4.4.6. Formal group definitions

The formal rules defining groups are as followed. Text in italic are comments about the rules.

For every class X:

  1. For each superclass Y of X, the group Y contains all constraints of the group Y of Y

    this rule prepares formal concepts for recursive discovery

  2. The group X contains the following constraints:

    group X is a group used on sequences redefining the default group on a class (see Section 4.4.3, “Redefining the Default group for a class”)

    1. every constraint declared by the class X which does not declare a group or does declare the group Default explicitly.

      all Default constraints hosted on X

    2. every constraint declared by any interface implemented by X and not annotated @GroupSequence which does not explicitly declare a group or does declare the group Default explicitly.

      all Default constraints hosted on interfaces of X: constraints are inherited by the class hierarchy. Interfaces marked as @GroupSequence are ignored.

    3. if X has a direct superclass Y, every constraint in the group Y

      all Default constraints hosted on the superclasses of X: constraints are inherited by the class hierarchy

  3. If X has no @GroupSequence annotation, the group Default contains the following constraints:

    this rule defines which constraints are evaluated when validating Default on X.

    1. every constraint in the group X

    2. if X has a direct superclass Y, every constraint in the group Default of Y

      this rule is necessary in case Y redefines the group Default

  4. If X does have a @GroupSequence annotation, the group Default contains every constraint belonging to every group declared by the @GroupSequence annotation.

    this rule describes how a class can redefine the group Default for itself (see Section 4.4.3, “Redefining the Default group for a class”)

    • the @GroupSequence annotation must declare the group X

  5. For every interface Z, the group Z contains the following constraints:

    this rule defines how non Default groups are defined

    1. every constraint declared by the interface Z which does not explicitly declare a group or does declare the group Default explicitly.

      all Default constraints hosted on Z: this rule formally defines implicit grouping per interface (see Section 4.4.4, “Implicit grouping”)

    2. every constraint (which does not explicitly declare a group) declared by any superinterface not annotated @GroupSequence of the interface Z

      all Default constraints hosted on interfaces of Z: groups can be inherited (see Section 4.4.1, “Group inheritance”)

    3. every constraint declared by the class X which explicitly declares the group Z

      every constraint hosted by X and marked as belonging to the group Z

    4. every constraint declared by any interface implemented by X and not annotated @GroupSequence which explicitly declares the group Z

      every constraint hosted by any interface of X and marked as belonging to the group Z

    5. if X has a direct superclass Y, every constraint in the group Z of Y

      every constraint hosted by any superclass of X and marked as belonging to the group Z

  6. For every interface Z annotated @GroupSequence, the group Z contains every constraint belonging to every group declared by the @GroupSequence annotation.

    defines the composition side of group sequence but does not define the ordering behavior of sequence (see Section 4.4.2, “Group sequence”)

When a given group G (represented by an interface G) is requested for the validation of a class X:

  • constraints belonging to the group G are evaluated

  • if the interface G is not annotated @GroupSequence, every group represented by the super interface of G are requested for validation

  • if the interface G is annotated with @GroupSequence, every group represented by the interfaces declared by the @GroupSequence annotation are requested for validation

    • the validation of groups declared to the @GroupSequence must happen in the sequencing order declared by @GroupSequence: the sequencing order is propagated to the groups composing the sequenced group (via inheritance or group sequence)

    • if a group validation triggers the failure of one or more constraints, groups following in the sequence must not be evaluated.

  • if the group G represents the Default group of X overridden by @GroupSequence, operations are equivalent

When the Default group of a given class X is overridden via @GroupSequence, its validation is as followed:

  • every group represented by the interfaces declared by the @GroupSequence annotation are requested for validation

    • the validation of groups declared to the @GroupSequence must happen in the sequencing order declared by @GroupSequence: the sequencing order is propagated to the groups composing the sequenced group (via inheritance or group sequence)

    • if a group validation triggers the failure of one or more constraints, groups following in the sequence must not be evaluated.

Unless defined by a @GroupSequence, evaluation ordering is not constrained. In particular, several groups can be validated in the same pass. If a group definition leads to a circular sequencing order between groups, a GroupDefinitionException is raised.

Note

A group G sequenced (directly or indirectly) to be executed before itself is not considered a circular reference.

4.5. Method and constructor constraints

Note

In the following, the term "method constraint" refers to constraints declared on methods as well as constructors.

Method constraints are declared by adding constraint annotations directly to methods or constructors and/or their parameters. In the former case, all the parameters of an executable (cross-parameter constraint) or the return value is constrained, in the latter individual parameters are constrained. As with bean constraints, this can be done using either actual Java annotations or using an XML constraint mapping file (see Section 8.1.1.5, “Method-level overriding”). Bean Validation providers are free to provide additional means of defining method constraints such as an API-based approach.

Getters are not considered constrained methods by default (see Section 10.1.2, “Method and constructor validation”).

4.5.1. Requirements on methods to be validated

Static methods are ignored by validation. Putting constraints on a static method is not portable. No other restrictions exist from the perspective of this specification, however it is possible that technologies integrating with method validation impose further restrictions to methods for which a validation shall be applied. For instance certain integration technologies might require that methods to be validated must have public visibility and/or must not be final.

4.5.2. Declaring parameter constraints

Parameter constraints are declared by putting constraint annotations on method or constructor parameters.

Example 4.12. Declaring parameter constraints

public class OrderService {

    public OrderService(@NotNull CreditCardProcessor creditCardProcessor) {
        [...]
    }

    public void placeOrder(
        @NotNull @Size(min=3, max=20) String customerCode,
        @NotNull Item item,
        @Min(1) int quantity) {
        [...]
    }
}

Using constraint annotations, several preconditions are defined here. These preconditions which must be satisfied in order to legally invoke the methods of OrderService are:

  • The CreditCardProcessor passed to the constructor must not be null.

  • The customer code passed to the placeOrder() method must not be null and must be between 3 and 20 characters long.

  • The Item passed to the placeOrder() method must not be null.

  • The quantity value passed to the placeOrder() method must be 1 at least.

Note that declaring these constraints does not automatically cause their validation when the concerned methods are invoked. It's the responsibility of an integration layer to trigger the validation of the constraints using a method interceptor, dynamic proxy or similar. See section Section 5.4, “Triggering method validation” for more details.

Tip

In order to use constraint annotations for method or constructor parameters, their element type must be ElementType.PARAMETER. In order to use constraint annotations for cross-parameter validation or on the return values of methods or constructors (see the following sections), their element type must be ElementType.METHOD respectively ElementType.CONSTRUCTOR. All built-in constraints support these element types and it is considered a best practice to do the same for custom constraints.

4.5.2.1. Cross-parameter constraints

Cross-parameter constraints allow to express constraints based on the value of several method parameters, similar to class-level constraints which are based on several properties of a given class. Cross-parameter constraints are declared by putting cross-parameter constraint annotations on methods or constructors as shown in the following example.

Example 4.13. Declaring cross-parameter constraints

public class CalendarService {

    @ConsistentDateParameters
    public void createEvent(
        String title,
        @NotNull Date startDate,
        @NotNull Date endDate) {
        [...]
    }
}

The cross-parameter constraint annotation expresses here that the given start date must be before the passed end date in order to legally invoke the createEvent() method. The example also shows that it is often useful to combine constraints directly placed on individual parameters (e.g. @NotNull) and cross-parameter constraints.

Tip

Cross-parameter constraints as well as return value constraints are declared directly on a method or a constructor. To make it obvious for a reader that an annotation refers to the parameters of a method or constructor and not its return value, it is recommended to chose a name which clearly expresses this intention.

It is not legal to declare a cross-parameter constraint on a method or constructor which has no parameters. A ConstraintDeclarationException is raised in this case.

Some constraints can target an executable's return value as well as its array of parameters. They are known to be both generic and cross-parameter constraints. When using such a constraint on an executable to target the parameters, one must set validationAppliesTo if there is an ambiguity. The set of ambiguities is described in Section 3.1.1.4, “validationAppliesTo”. Even without ambiguity, it is recommended to explicitly set validationAppliesTo to ConstraintTarget.PARAMETERS as it improves readability.

4.5.2.2. Naming parameters

In case the validation of a parameter constraint fails, the concerned parameter needs to be identified in the resulting ConstraintViolation (see section Section 5.2, “ConstraintViolation”). As of version 7, Java doesn't provide a portable way to retrieve parameter names. Bean Validation therefore defines the javax.validation.ParameterNameProvider API to which the retrieval of parameter names is delegated:

/**
 * Provides names for method and constructor parameters.
 * <p/>
 * Used by the Bean Validation runtime when creating constraint violation
 * objects for violated method constraints.
 * <p/>
 * Implementations must be thread-safe.
 *
 * @author Gunnar Morling
 * @since 1.1
 */
public interface ParameterNameProvider {

    /**
     * Returns the names of the parameters of the given constructor.
     *
     * @param constructor the constructor for which the parameter names shall be
     *        retrieved; never {@code null}
     * @return a list containing the names of the parameters of the given
     *         constructor; may be empty but never {@code null}
     */
    List<String> getParameterNames(Constructor<?> constructor);

    /**
     * Returns the names of the parameters of the given method.
     *
     * @param method the method for which the parameter names shall be retrieved;
     *        never {@code null}
     * @return a list containing the names of the parameters of the given method;
     *         may be empty but never {@code null}
     */
    List<String> getParameterNames(Method method);
}

A conforming Bean Validation implementation provides a default ParameterNameProvider implementation which returns parameter names in the form argPARAMETER_INDEX, where PARAMETER_INDEX starts at 0 for the first parameter, e.g. arg0, arg1 etc.

Bean Validation providers and integrators are free to provide additional implementations (e.g. based on annotations specifying parameter names, debug symbols etc.). If a user wishes to use another parameter name provider than the default implementation, she may specify the provider to use with help of the bootstrap API (see Section 5.5, “Bootstrapping”) or the XML configuration (see Section 5.5.6, “XML configuration: META-INF/validation.xml”).

If an exception occurs during invocation of the getParameterNames() methods, this exception is wrapped into a ValidationException by the Bean Validation engine.

4.5.3. Declaring return value constraints

Return value constraints are declared by putting constraint annotations directly on a method or constructor.

Some constraints can target both the return value and the array of parameters of an executable. They are known to be both generic and cross-parameter constraints. When using such constraint on an executable to target the return value, one must set validationAppliesTo in case there is an ambiguity. The set of ambiguities is described in Section 3.1.1.4, “validationAppliesTo”. Even without ambiguity, it is recommended to explicitly set validationAppliesTo to ConstraintTarget.RETURN_VALUE as it improves readability.

Example 4.14. Declaring return value constraints

public class OrderService {

    private CreditCardProcessor creditCardProcessor;

    @ValidOnlineOrderService
    public OrderService(OnlineCreditCardProcessor creditCardProcessor) {
        this.creditCardProcessor = creditCardProcessor;
    }

    @ValidBatchOrderService
    public OrderService(BatchCreditCardProcessor creditCardProcessor) {
        this.creditCardProcessor = creditCardProcessor;
    }

    @NotNull
    @Size(min=1)
    public Set<CreditCardProcessor> getCreditCardProcessors() { [...] }

    @NotNull
    @Future
    public Date getNextAvailableDeliveryDate() { [...] }
}

Here the following postconditions are defined which are guaranteed to the caller of the methods and constructors of the OrderService class:

  • The newly created OrderService object returned by the first constructor satisfies the conditions of the custom @ValidOnlineOrderService constraint.

  • The newly created OrderService object returned by the second constructor satisfies the conditions of the custom @ValidBatchOrderService constraint.

  • The set of CreditCardProcessor objects returned by getCreditCardProcessors() will neither be null nor be empty.

  • The Date object returned by getNextAvailableDeliveryDate() will not be null and will be in the future.

Like parameter constraints, these return value constraints are not per-se validated upon method invocation, but instead an integration layer invoking the validation is required.

4.5.4. Marking parameters and return values for cascaded validation

The @Valid annotation is used to declare that a cascaded validation of the given method/constructor parameters or return values is performed by the Bean Validation provider. When marked, the parameter or return value is considered a bean object to validate. The same rules as for standard object graph validation (see Section 4.6.1, “Object graph validation”) apply, in particular

  • null arguments and null return values are ignored

  • The validation is recursive; that is, if validated parameter or return value objects have references marked with @Valid themselves, these references will also be validated

  • Bean Validation providers must guarantee the prevention of infinite loops during cascaded validation

Example 4.15. Marking parameters and return values for cascaded validation

public class OrderService {

    @NotNull @Valid
    private CreditCardProcessor creditCardProcessor;

    @Valid
    public OrderService(@NotNull @Valid CreditCardProcessor creditCardProcessor) {
        this.creditCardProcessor = creditCardProcessor;
    }

    @NotNull @Valid
    public Order getOrderByPk(@NotNull @Valid OrderPK orderPk) { [...] }

    @NotNull @Valid
    public Set<Order> getOrdersByCustomer(@NotNull @Valid CustomerPK customerPk) { [...] }
}

Here the following recursive validations will happen when validating the methods of the OrderService class:

  • Validation of the constraints on the object passed for the creditCardProcessor parameter of the constructor

  • Validation of the constraints on the newly created OrderService instance returned by the constructor, i.e. the @NotNull constraint on the field creditCardProcessor and the constraints on the referenced CreditCardProcessor instance (as the field is annotated with @Valid).

  • Validation of the constraints on the object passed for the orderPk parameter and the returned Order object of the getOrderByPk() method

  • Validation of the constraints on the object passed for the customerPk parameter and the constraints on each object contained within the returned Set<Order> of the getOrdersByCustomer() method

Again, solely marking parameters and return values for cascaded validation does not trigger the actual validation.

4.5.5. Method constraints in inheritance hierarchies

When defining method constraints within inheritance hierarchies (that is, class inheritance by extending base classes and interface inheritance by implementing or extending interfaces) one has to obey the Liskov substitution principle which mandates that:

  • a method's preconditions (as represented by parameter constraints) must not be strengthened in sub types

  • a method's postconditions (as represented by return value constraints) must not be weakened in sub types

Tip

Very informally speaking, the Liskov substitution principle says that where a given type T is used, it should be possible to replace T with a sub-type S of T ("Behavioral subtyping"). If S overrides/implements a method from T and S would strengthen the method's preconditions (e.g. by adding parameter constraints) this principle would be violated as client code working correctly against T might fail when working against S. Also if S overrides/implements a method from T and S weakens the method's postconditions this principle would be violated. However S may strengthen the method's postconditions (by adding return value constraints), as client code working against T still will work against S.

Therefore the following rules with respect to the definition of method level constraints in inheritance hierarchies apply:

  • In sub types (be it sub classes/interfaces or interface implementations), no parameter constraints may be declared on overridden or implemented methods, nor may parameters be marked for cascaded validation. This would pose a strengthening of preconditions to be fulfilled by the caller.

  • If a sub type overrides/implements a method originally defined in several parallel types of the hierarchy (e.g. two interfaces not extending each other, or a class and an interface not implemented by said class), no parameter constraints may be declared for that method at all nor parameters be marked for cascaded validation. This again is to avoid an unexpected strengthening of preconditions to be fulfilled by the caller.

  • In sub types (be it sub classes/interfaces or interface implementations), return value constraints may be declared on overridden or implemented methods and the return value may be marked for cascaded validation. Upon validation, all return value constraints of the method in question are validated, wherever they are declared in the hierarchy. This only poses possibly a strengthening but no weakening of the method's postconditions guaranteed to the caller.

  • One must not mark a method return value for cascaded validation more than once in a line of a class hierarchy. In other words, overriding methods on sub types (be it sub classes/interfaces or interface implementations) cannot mark the return value for cascaded validation if the return value has already been marked on the overridden method of the super type or interface.

Out of the box, a conforming Bean Validation provider must throw a ConstraintDeclarationException when discovering that any of these rules are violated. In addition providers may implement alternative, potentially more liberal, approaches for handling constrained methods in inheritance hierarchies. Possible means for activating such alternative behavior include provider-specific configuration properties or annotations. Note that client code relying on such alternative behavior is not portable between Bean Validation providers.

The above rules do not apply when validating constructor constraints as constructors do not override one another. Parameter and return value constraints can be applied to any constructor in the type hierarchy, but only the constraints defined directly on the validated constructor are evaluated.

4.5.5.1. Examples

This sections provides some examples of illegal constraint definitions which violate the rules stated above in one way or another.

Example 4.16. Illegally declared parameter constraints on interface implementation

public interface OrderService {

    void placeOrder(String customerCode, Item item, int quantity);
}

public class SimpleOrderService implements OrderService {

    @Override
    public void placeOrder(
        @NotNull @Size(min=3, max=20) String customerCode,
        @NotNull Item item,
        @Min(1) int quantity) {
        [...]
    }
}

The constraints in SimpleOrderService are illegal, as they strengthen the preconditions of the placeOrder() method as constituted by the interface OrderService.

Example 4.17. Illegally declared parameter constraints on sub class

public class OrderService {

    void placeOrder(String customerCode, Item item, int quantity) { [...] }
}

public class SimpleOrderService extends OrderService {

    @Override
    public void placeOrder(
        @NotNull @Size(min=3, max=20) String customerCode,
        @NotNull Item item,
        @Min(1) int quantity) {
        [...]
    }
}

The constraints in SimpleOrderService are illegal, as they strengthen the preconditions of the placeOrder() method as constituted by the super class OrderService.

Example 4.18. Illegally declared parameter constraints on parallel types

public interface OrderService {

    void placeOrder(String customerCode, Item item, int quantity);
}

public interface OrderPlacementService {

    public void placeOrder(
        @NotNull @Size(min=3, max=20) String customerCode,
        @NotNull Item item,
        @Min(1) int quantity);
}

public class SimpleOrderService implements OrderService, OrderPlacementService {

    @Override
    public void placeOrder(String customerCode, Item item, int quantity) {
        [...]
    }
}

Here the class SimpleOrderService implements the interfaces OrderService and OrderPlacementService, which themselves are unrelated to each other but both define a method placeOrder() with an identical signature. This hierarchy is illegal with respect to the parameter constraints as a client of SimpleOrderService would have to fulfill the constraints defined on the interface OrderPlacementService even if the client only expects OrderService.

Example 4.19. Correctly declared return value constraints on sub class

public class OrderService {

    Order placeOrder(String customerCode, Item item, int quantity) {
        [...]
    }
}

public class SimpleOrderService extends OrderService {

    @Override
    @NotNull
    @Valid
    public Order placeOrder(String customerCode, Item item, int quantity) {
        [...]
    }
}

The return value constraints in DefaultOrderService are legal, as they strengthen the postconditions of the placeOrder() method as constituted by the super class OrderService but don't weaken them.

4.6. Validation routine

For a given group, the validation routine applied on a given bean instance is expected to execute the following constraint validations in no particular order:

  • for all reachable fields, execute all field level validations (including the ones expressed on superclasses) matching the targeted group unless the given validation constraint has already been processed during this validation routine for a given navigation path (see Section 4.6.1, “Object graph validation”) as part of a previous group match.

  • for all reachable getters, execute all getter level validations (including the ones expressed on interfaces and superclasses) matching the targeted group unless the given validation constraint has already been processed during this validation routine for a given navigation path (see Section 4.6.1, “Object graph validation”) as part of a previous group match.

  • execute all class level validations (including the ones expressed on interfaces and superclasses) matching the targeted group unless the given validation constraint has already been processed during this validation routine for a given navigation path (see Section 4.6.1, “Object graph validation”) as part of a previous group match.

  • for all reachable and cascadable associations, execute all cascading validations (see Section 4.6.1, “Object graph validation”) including the ones expressed on interfaces and superclasses (see Section 4.4.6, “Formal group definitions”). Note that group conversion can apply (see Section 4.4.5, “Group conversion”).

Reachable fields, getters and associations as well as cascadable associations are defined in Section 4.6.3, “Traversable property”.

Note that this implies that a given validation constraint will not be processed more than once per validation per path. Some implementations might even process a single constraint only once across paths provided that they return the expected set of ConstraintViolation.

Unless ordered by group sequences, groups can be validated in no particular order. This implies that the validation routine can be run for several groups in the same pass.

The object validation routine is described as such. For each constraint declaration:

4.6.1. Object graph validation

The @Valid annotation on a given association (i.e. object reference or collection, array, Iterable of objects), dictates the Bean Validator implementation to apply recursively the Bean Validation routine on (each of) the associated object(s). This mechanism is recursive: an associated object can itself contain cascaded references.

Null references are ignored.

To prevent infinite loops, the Bean Validation implementation must ignore the cascading operation if the associated object instance has already been validated in the current navigation path (starting from the root object). See Example 4.20, “Object graph limits” for an example. A navigation path is defined as a set of @Valid associations starting from the root object instance and reaching the associated instance. A given navigation path cannot contain the same instance multiple times (the complete validated object graph can though). See Example 4.20, “Object graph limits” for an example.

Note

This object graph navigation can lead to multiple validations of the same constraint and the same object instance but the set of constraint validation is deterministic and the algorithm prevents infinite loops.

Example 4.20. Object graph limits

#assuming the following object graph

Order -(lines)-> Orderline1
Order -(lines)-> Orderline2
Orderline1 -(order)-> Order
Orderline2 -(order)-> Order
Order -(customer)-> User
Order -(shippingAddress)-> Address1
Order -(billingAddress)-> Address2
Address1 -(inhabitant)-> User
Address2 -(inhabitant)-> User
User -(addresses)-> Address1
User -(addresses)-> Address2

#validation branches are as followed
Order -(lines)-> Orderline1
  - order is ignored: Order is already present in the branch 

Order -(lines)-> Orderline2
  - order is ignored: Order is already present in the branch

Order -(customer)-> User -(addresses)-> Address1
  - inhabitant is ignored: User is already present in the branch

Order -(customer)-> User -(addresses)-> Address2
  - inhabitant is ignored: User is already present in the branch

Order -(shippingAddress)-> Address1 -(inhabitant)-> User 
  - addresses to Address1 is ignored: Address1 is already present in the branch

Order -(shippingAddress)-> Address1 -(inhabitant)-> User -(addresses)-> Address2
  - inhabitant is ignored: User is already present in the branch

Order -(billingAddress)-> Address2 -(inhabitant)-> User 
  - addresses to Address2 is ignored: Address2 is already present in the branch

Order -(billingAddress)-> Address2 -(inhabitant)-> User -(addresses)-> Address1
  - inhabitant is ignored: User is already present in the branch

The ConstraintViolation objects are built when a failing constraint on an associated object is found. They reflect the path to reach the object from the root validated object (See Section 5.2, “ConstraintViolation”).

@Valid is an orthogonal concept to the notion of group. If two groups are in sequence, the first group must pass for all associated objects before the second group is evaluated. Note however that the Default group sequence overriding is local to the class it is defined on and is not propagated to the associated objects. The following example illustrates this:

Example 4.21. Class Driver with redefined default group

@GroupSequence({ Minimal.class, Driver.class })
public class Driver {
  @Min(value = 18, groups = Minimal.class)
  int age;

  @AssertTrue
  Boolean passedDrivingTest;

  @Valid
  Car car;

  // setter/getters
}

Example 4.22. Class Car with redefined default group

@GroupSequence({ Car.class, Later.class })
public class Car {
  @NotNull
  String type;

  @AssertTrue(groups = Later.class)
  Boolean roadWorthy;

  // setter/getters
}

Example 4.23. Defining a group sequence

@GroupSequence({ Minimal.class, Later.class })
public interface SequencedGroups {
}

Example 4.24. Group sequence overriding is not propagated to associated objects

Validator validator = Validation.buildDefaultValidatorFactory().getValidator();

Driver driver = new Driver();
driver.setAge(16);
Car porsche = new Car();
driver.setCar(porsche);


Set<ConstraintViolation<Driver>> violations = validator.validate( driver );

assert violations.size() == 2;

violations = validator.validate( driver, SequencedGroups.class );

assert violations.size() == 1;

The default group sequence is redefined for the Driver as well as Car. When the default group is requested via validator.validate( driver ) the group Minimal gets validated in class Driver. The constraint will fail since the driver's age in the example is only 16. The constraint on passedDrivingTest will not be evaluated due to the redefined default sequence of Driver. However, there is one more constraint violation, namely the @NotNull on Car.type. The reason for this is that the group Default gets propagated to Car (not Minimal). Class Driver defines its own group sequence which means that only @NotNull on type gets evaluated.

In the second call to validate the group SequencedGroups is requested which defines a sequence of Minimal followed by Later. In this case there is only one constraint violation. Again @Min on age fails, but in this case the group Minimal gets propagated to Car which does not have any constraints defined against this group. Constraints belonging to the group Later won't get validated until all constraints belonging to Minimal pass.

4.6.2. Method and constructor validation

For a given group, the validation routine applied to validate parameters of a method or constructor is expected to execute the following constraint validations in no particular order:

  • execute all parameter validations (in case of overriding method validation, including the ones expressed on overridden methods of the interfaces and superclasses) matching the targeted group unless the given validation constraint has already been processed during this validation routine for a given navigation path (see Section 4.6.1, “Object graph validation”) as part of a previous group match.

  • execute all cross parameter validations (in case of overriding method validation, including the ones expressed on overridden methods of the interfaces and superclasses) matching the targeted group unless the given validation constraint has already been processed during this validation routine for a given navigation path (see Section 4.6.1, “Object graph validation”) as part of a previous group match.

  • for all parameters marked for cascaded validation, execute all cascading validations (see Section 4.6.1, “Object graph validation”), in case of overriding method validation including the ones expressed on overridden methods of the interfaces and superclasses (see Section 4.4.6, “Formal group definitions”). Note that group conversion can apply (see Section 4.4.5, “Group conversion”).

For a given group, the validation routine applied to validate the return value of a method or constructor is expected to execute the following constraint validations in no particular order:

Note that this implies that a given validation constraint will not be processed more than once per validation per path. Some implementations might even process a single constraint only once across paths provided that they return the expected set of ConstraintViolation.

Unless ordered by group sequences, groups can be validated in no particular order. This implies that the validation routine can be run for several groups in the same pass.

The object validation routine is as defined in described in Section 4.6, “Validation routine”.

4.6.3. Traversable property

In some cases, the state of some properties should not be accessed. For example, if a property loaded by a Java Persistence provider is a lazy property or a lazy association, accessing its state would trigger a load from the database. An undesired behavior.

Bean Validation offers a way to control which property can and cannot be accessed via the TraversableResolver.isReachable() contract.

Likewise, it is sometimes undesirable to cascade validation despite the use of @Valid. Java Persistence 2 for example does not cascade to associated entities during flush. You can control this behavior by implementing Traversable.isCascadable().

/**
 * Contract determining if a property can be accessed by the Bean Validation provider.
 * This contract is called for each property that is being either validated or cascaded.
 * <p/>
 * A traversable resolver implementation must be thread-safe.
 *
 * @author Emmanuel Bernard
 */
public interface TraversableResolver {
    /**
     * Determines if the Bean Validation provider is allowed to reach the property state.
     *
     * @param traversableObject object hosting {@code traversableProperty}
     *        or {@code null} if {@code validateValue} is called
     * @param traversableProperty the traversable property
     * @param rootBeanType type of the root object passed to the Validator
     *        or hosting the method or constructor validated
     * @param pathToTraversableObject path from the root object to
     *        {@code traversableObject}
     *        (using the path specification defined by Bean Validator)
     * @param elementType either {@code FIELD} or {@code METHOD}
     * @return {@code true} if the Bean Validation provider is allowed to
     *         reach the property state, {@code false} otherwise
     */
    boolean isReachable(Object traversableObject,
                        Node traversableProperty,
                        Class<?> rootBeanType,
                        Path pathToTraversableObject,
                        ElementType elementType);

    /**
     * Determines if the Bean Validation provider is allowed to cascade validation on
     * the bean instance returned by the property value
     * marked as {@code @Valid}.
     * <p/>
     * Note that this method is called only if
     * {@link #isReachable(Object, javax.validation.Path.Node, Class, Path, java.lang.annotation.ElementType)}
     * returns {@code true} for the same set of arguments and if the property
     * is marked as {@link Valid}.
     *
     * @param traversableObject object hosting {@code traversableProperty}
     *        or {@code null} if {@code validateValue} is called
     * @param traversableProperty the traversable property
     * @param rootBeanType type of the root object passed to the Validator
     *        or hosting the method or constructor validated
     * @param pathToTraversableObject path from the root object to
     *        {@code traversableObject}
     *        (using the path specification defined by Bean Validator)
     * @param elementType either {@code FIELD} or {@code METHOD}
     * @return {@code true} if the Bean Validation provider is allowed to
     *         cascade validation, {@code false} otherwise
     */
    boolean isCascadable(Object traversableObject,
                         Node traversableProperty,
                         Class<?> rootBeanType,
                         Path pathToTraversableObject,
                         ElementType elementType);
}

isReachable() is called for every property about to be accessed either for validation or for cascading. A property is reachable if this method returns true.

isCascadable() is called for every property about to be cascaded (i.e. marked as @Valid). A property is cascadable if it is reachable and if the isCascadable method returns true.

Note

isCascadable() for a given property is only called if isReachable() returns true. In other words, isReachable() is always called before isCascadable() for a given property.

traversableObject is the object instance being evaluated. null if the check is triggered as part of a validateValue() call.

traversableProperty is the Node representing the property hosted by the traversableObject being considered for traversal. The name of a property is defined in Section 4.1.2, “Field and property validation”.

rootBeanType is the class of the root being validated, i.e. either the type of the object passed to the validate method or the type declaring the validated method/constructor in case of method validation).

pathToTraversableObject is the Path from the rootBeanType down to the traversableObject. If the root object is traversableObject, pathToTraversableObject is composed of a single Node whose name is null. The path is described following the conventions described in Section 5.2, “ConstraintViolation” (getPropertyPath).

elementType is the java.lang.annotation.ElementType the annotation is placed on. It can be either FIELD or METHOD. Any other value is not expected.

The Bean Validation provider must not access the state of a property, nor validate its constraints if the property is not traversable. A property is traversable if TraversableResolver returns true for this property.

If an exception occurs when the TraversableResolver is called, the exception is wrapped into a ValidationException.

The following elements are not passed through the traversable resolver filter:

  • the bean instance validated

  • the method and constructor parameter values being validated

  • the method and constructor return value being validated

But the properties of these elements (if validated) are. In this case the complete path is provided via pathToTraversableObject.

The traversable resolver used by default by a Bean Validation provider behaves as followed:

  • if Java Persistence is available in the runtime environment, a property is considered reachable if Java Persistence considers the property as loaded. A typical implementation will use Persistence.getPersistenceUtil().isLoaded(Object, String) to implement such contract.

  • if Java Persistence is not available in the runtime environment, all properties are considered reachable.

  • all properties are considered cascadable.

An example implementation of such a resolver is shown in Example 4.25, “Java Persistence aware TraversableResolver”.

Example 4.25. Java Persistence aware TraversableResolver

public class JPATraversableResolver implements TraversableResolver {

    public boolean isReachable(Object traversableObject,
                               Path.Node traversableProperty,
                               Class<?> rootBeanType,
                               Path pathToTraversableObject,
                               ElementType elementType) {
        return traversableObject == null ||
                Persistence.getPersistenceUtil().isLoaded(
                        traversableObject,
                        traversableProperty.getName() );
    }

    public boolean isCascadable(Object traversableObject,
                               Path.Node traversableProperty,
                               Class<?> rootBeanType,
                               Path pathToTraversableObject,
                               ElementType elementType) {
        return true;
    }
}

See Section 5.5, “Bootstrapping” to how to pass a custom TraversableResolver.

4.6.3.1. Examples

The following example assumes the object graph defined in Example 4.26, “Definitions used in the example” and assumes the validation operation is applied on an address object.

Example 4.26. Definitions used in the example

public class Country {
    @NotNull private String name;
    @Size(max=2) private String ISO2Code;
    @Size(max=3) private String ISO3Code;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getISO2Code() {
        return ISO2Code;
    }

    public void setISO2Code(String ISO2Code) {
        this.ISO2Code = ISO2Code;
    }

    public String getISO3Code() {
        return ISO3Code;
    }

    public void setISO3Code(String ISO3Code) {
        this.ISO3Code = ISO3Code;
    }
}

public class Address {
    @NotNull @Size(max=30)
    private String addressline1;
    @Size(max=30)
    private String addressline2;
    @Size(max=11)
    private String zipCode;
    @Valid
    private Country country;

    private String city;

    public String getAddressline1() {
        return addressline1;
    }

    public void setAddressline1(String addressline1) {
        this.addressline1 = addressline1;
    }

    public String getAddressline2() {
        return addressline2;
    }

    public void setAddressline2(String addressline2) {
        this.addressline2 = addressline2;
    }

    public String getZipCode() {
        return zipCode;
    }

    public void setZipCode(String zipCode) {
        this.zipCode = zipCode;
    }

    @Size(max=30) @NotNull
    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public Country getCountry() {
        return country;
    }

    public void setCountry(Country country) {
        this.country = country;
    }
}

When the Bean Validation provider is about to check constraints of ISO3Code, it calls the TraversableResolver.isReachable() method to ensure that the ISO3Code property is reachable with the following parameter values:

  • traversableObject: country. The instance returned by address.getCountry().

  • traversableProperty: a PropertyNode whose name is "ISO3Code". Represents the property of traversableObject being verified.

  • rootBeanType: Address.class. The type of the root object being validated.

  • pathtoTraversableObject: a Path containing a single PropertyNode whose name is "country". The path from address to the country instance.

  • elementType: ElementType.FIELD. The ISO3Code property is annotated on its field.

When the Bean Validation provider is about to cascade validation on country (Address object), it calls the TraversableResolver.isReachable() method to ensure that the country property is reachable and if this method returns true, it calls TraversableResolver.isCascadable() with the following parameter values:

  • traversableObject: address. The address instance.

  • traversableProperty: a PropertyNode whose name is "country". Represents the property of traversableObject being verified.

  • rootBeanType: Address.class. The type of the root object being validated.

  • pathtoTraversableObject: a Path containing a single BeanNode whose name is null.

  • elementType: ElementType.FIELD. The country property is annotated on its field.

The following example shows invocations of the TraversableResolver as to be performed by the Bean Validation provider during method validation. The example is based on the object graph defined in Example 4.26, “Definitions used in the example” and the AddressService class shown in Example 4.27, “Examplary class AddressService”. It assumes that a call of persistAddress() is subject to method parameter validation.

Example 4.27. Examplary class AddressService

public class AddressService {
    public void persistAddress(@NotNull @Valid Address address) {
        [...]
    }
}

When the Bean Validation provider is about to validate the @NotNull constraint on the address parameter, no call to isReachable() is expected, since parameters are assumed to always be reachable. Similarly, no call to isCascable() is expected when performing cascaded validation of the address parameter, since parameters are assumed to always be cascadable.

When the Bean Validation provider is about to validate constraints on the field addressline1 of the passed Address object, it calls the isReachable() method to ensure that the property is reachable with the following parameter values:

  • traversableObject: address. The instance passed to persistAddress().

  • traversableProperty: a PropertyNode whose name is "addressline1". Represents the property of traversableObject being verified.

  • rootBeanType: AddressService.class. The type of the root object being validated.

  • pathtoTraversableObject: a Path comprising a MethodNode (named "persistService") and a ParameterNode (with parameter index 0). The path from AddressService to the Address instance.

  • elementType: ElementType.FIELD. The addressline1 property is annotated on its field.

When the Bean Validation provider is about to perform a cascaded validation of the country property of the passed Address object, it calls the isReachable() method to ensure that the property is reachable. If this method returns true, it calls TraversableResolver.isCascadable() with the following parameter values:

  • traversableObject: address. The instance passed to persistAddress().

  • traversableProperty: a PropertyNode whose name is "country". Represents the property of traversableObject being verified.

  • rootBeanType: AddressService.class. The type of the root object being validated.

  • pathtoTraversableObject: a Path comprising a MethodNode (named "persistService") and a ParameterNode (with parameter index 0). The path from AddressService to the Address instance.

  • elementType: ElementType.FIELD. The country property is annotated on its field.

4.6.4. ConstraintValidator resolution algorithm

A constraint is associated to one or more ConstraintValidator implementations. Each ConstraintValidator<A, T> accepts the type T. The ConstraintValidator executed depends on the type hosting the constraint. For a given constraint evaluation, a single ConstraintValidator is considered.

The list of ConstraintValidators can contain at most one which targets cross-parameter. If the constraint targets the parameters of an executable either implicitly or by the use of validationAppliesTo in the constraint - see Section 3.1.1.4, “validationAppliesTo”, then the cross-parameter ConstraintValidator is used. If none is present, a ConstraintDefinitionException is raised. If more than one cross-parameter ConstraintValidator is present, a ConstraintDefinitionException is raised.

If the constraint is a generic constraint, the following rules apply. If the constraint declaration is hosted on a class or an interface, the targeted type is the class or the interface. If the constraint is hosted on a class attribute, the type of the attribute is the targeted type. If the constraint is hosted on a getter, the return type of the getter is the targeted type. In other words, the resolution algorithm considers the type as defined in the method signature and not the runtime type of the value.

The rules written below describe formally the following statement: the ConstraintValidator chosen to validate the generic constraint on a declared type T is the one where the ConstraintValidator targets the annotated element, where the type supported by the ConstraintValidator is a supertype of T and where there is no other ConstraintValidator whose supported type is a supertype of T and not a supertype of the chosen ConstraintValidator supported type.

When validating a generic constraint A placed on a target declaring the type T, the following resolution rules apply:

  • Only ConstraintValidator implementations targeting annotated elements are considered.

  • Primitive types are considered equivalent to their respective primitive wrapper class.

  • A ConstraintValidator<A, U> is said to be compliant with T if T is a subtype of U (according to the Java Language Specification 3rd edition chapter 4.10 Subtyping). Note that T is a subtype of U if T = U.

  • If no ConstraintValidator compliant with T is found amongst the ConstraintValidators listed by the constraint A, an UnexpectedTypeException is raised.

  • A ConstraintValidator<A, U> compliant with T is considered strictly more specific than a ConstraintValidator<A, V> compliant with T if U is a strict subtype of V. U is a strict subtype of V if U is a subtype of V and U != V (according to the Java Language Specification 3rd edition chapter 4.10 Subtyping).

  • A ConstraintValidator<A, U> compliant with T is considered maximally specific if no other ConstraintValidator<A, V> compliant with T is strictly more specific than ConstraintValidator<A, U>.

  • If more than one maximally specific ConstraintValidator is found, an UnexpectedTypeException is raised.

Note

While the Java compiler itself cannot determine if a constraint declaration will lead to a UnexpectedTypeException, rules can be statically checked. A tool such as an IDE or a Java 6 annotation processor can apply these rules and prevent compilation in case of ambiguity. The specification encourages Bean Validation providers to provide such a tool to their users.

Let's see a couple of declarations and their respective ConstraintValidator resolution. Assuming the definitions shown in Example 4.28, “ConstraintValidator and type resolution”:

Example 4.28. ConstraintValidator and type resolution

[...]
@Constraint(validatedBy={
    SizeValidatorForCollection.class,
    SizeValidatorForSet.class,
    SizeValidatorForSerializable.class })
public @interface Size { [...] }

public class SizeValidatorForCollection implements ConstraintValidator<Size, Collection> {
    [...]
}
public class SizeValidatorForSet implements ConstraintValidator<Size, Set> {
    [...]
}
public class SizeValidatorForSerializable implements ConstraintValidator<Size, Serializable> {
    [...]
}

public interface SerializableCollection extends Serializable, Collection {
}

The resolutions shown in Table 4.1, “Resolution of ConstraintValidator for various constraints declarations” occur.

Table 4.1. Resolution of ConstraintValidator for various constraints declarations

DeclarationResolution
@Size Collection getAddresses() { [...] }SizeValidatorForCollection: direct match
@Size Collection<?> getAddresses() { [...] }SizeValidatorForCollection: Collection is a direct supertype of Collection<?>
@Size Collection<Address> getAddresses() { [...] }SizeValidatorForCollection: Collection is a direct supertype of Collection<Address>
@Size Set<Address> getAddresses() { [...] }SizeValidatorForSet: direct supertype of Set<Address>
@Size SortedSet<Address> getAddresses() { [...] }SizeValidatorForSet: Set is the closest supertype of SortedSet<Address>
@Size SerializableCollection getAddresses() { [...] }UnexpectedTypeException: SerializableCollection is a subtype of both Collection and Serializable and neither Collection nor Serializable are subtypes of each other.
@Size String getName() { [...] }UnexpectedTypeException: none of the ConstraintValidator types are supertypes of String.

4.7. Examples

The first example demonstrates how beans, fields and getters are annotated to express some constraints.

Example 4.29. Place constraint declarations on the element to validate

@ZipCodeCityCoherenceChecker
public class Address {
    @NotNull @Size(max=30)
    private String addressline1;

    @Size(max=30)
    private String addressline2;

    private String zipCode;

    private String city;

    public String getAddressline1() {
        return addressline1;
    }

    public void setAddressline1(String addressline1) {
        this.addressline1 = addressline1;
    }

    public String getAddressline2() {
        return addressline2;
    }

    public void setAddressline2(String addressline2) {
        this.addressline2 = addressline2;
    }

    public String getZipCode() {
        return zipCode;
    }

    public void setZipCode(String zipCode) {
        this.zipCode = zipCode;
    }

    @Size(max=30) @NotNull
    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }
}

During the validation routine execution on an Address object,

  • addressline1 field value is passed to the @NotNull as well as @Size constraint validation implementation.

  • addressline2 field value is passed to the @Size constraint validation implementation.

  • getCity value is passed to the @Size and @NotNull constraint validation implementations

  • @ZipCodeCoherenceChecker is a constraint whose validation implementation's isValid method receives the Address object

The second example demonstrates object graph validation

Example 4.30. Define object graph validation

public class Country {
    @NotNull
    private String name;
    @Size(max=2) private String ISO2Code;
    @Size(max=3) private String ISO3Code;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getISO2Code() {
        return ISO2Code;
    }

    public void setISO2Code(String ISO2Code) {
        this.ISO2Code = ISO2Code;
    }

    public String getISO3Code() {
        return ISO3Code;
    }

    public void setISO3Code(String ISO3Code) {
        this.ISO3Code = ISO3Code;
    }
}

public class Address {
    @NotNull @Size(max=30)
    private String addressline1;
    @Size(max=30)
    private String addressline2;
    @Size(max=11)
    private String zipCode;
    @NotNull @Valid
    private Country country;

    private String city;

    public String getAddressline1() {
        return addressline1;
    }

    public void setAddressline1(String addressline1) {
        this.addressline1 = addressline1;
    }

    public String getAddressline2() {
        return addressline2;
    }

    public void setAddressline2(String addressline2) {
        this.addressline2 = addressline2;
    }

    public String getZipCode() {
        return zipCode;
    }

    public void setZipCode(String zipCode) {
        this.zipCode = zipCode;
    }

    @Size(max=30) @NotNull
    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }

    public Country getCountry() {
        return country;
    }

    public void setCountry(Country country) {
        this.country = country;
    }
}

During the validation routine execution on an Address object, constraints on addressLine1, addressLine2, zipCode, getCity and country are processed as well as the validation of the Country object itself, more specifically country.name is checked for @NotNull, ISO2Code and ISO3Code are checked for @Size.

Assuming that @NotEmpty is defined as such

package com.acme.constraint;

@Documented
@NotNull
@Size(min=1)
@ReportAsSingleViolation
@Constraint(validatedBy = NotEmpty.NotEmptyValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface NotEmpty {
    String message() default "{com.acme.constraint.NotEmpty.message}"
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        NotEmpty[] value();
    }    

    class NotEmptyValidator implements ConstraintValidator<NotEmpty, String> {
        public void initialize(NotEmpty constraintAnnotation) {}

        public boolean isValid(String value, ConstraintValidatorContext context) {
            return true;
        }
    }
}

The third example demonstrates superclass, inheritance and composite constraints.

Example 4.31. Use inheritance, constraints on superclasses and composite constraints

public interface Person {
    @NotEmpty
    String getFirstName();

    String getMiddleName();
    
    @NotEmpty
    String getLastName();
}

public class Customer implements Person {
    private String firstName;
    private String middleName;
    private String lastName;
    @NotNull
    private String customerId;
    @Password(robustness=5)
    private String password;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getMiddleName() {
        return middleName;
    }

    public void setMiddleName(String middleName) {
        this.middleName = middleName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getCustomerId() {
        return customerId;
    }

    public void setCustomerId(String customerId) {
        this.customerId = customerId;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

public class PreferredGuest extends Customer {
    @CreditCard
    private String guestCreditCardNumber;

    public String getGuestCreditCardNumber() {
        return guestCreditCardNumber;
    }

    public void setGuestCreditCardNumber(String guestCreditCardNumber) {
        this.guestCreditCardNumber = guestCreditCardNumber;
    }
}

public class CommonGuest extends customer {}

When validating a PreferredGuest the following constraints are processed:

  • @NotEmpty, @NotNull and @Size(min=1) on firstName

  • @NotEmpty, @NotNull and @Size(min=1) on lastName

  • @NotNull on customerId, @Password on password

  • @CreditCard on guestCreditCardNumber

When validating CommonGuest, the following constraints are processed:

  • @NotEmpty, @NotNull and @Size(min=1) on firstName

  • @NotEmpty, @NotNull and @Size(min=1) on lastName

  • @NotNull on customerId, @Password on password

The fourth example demonstrates the influence of group sequence.

Example 4.32. Use groups and group sequence to define constraint ordering

@GroupSequence({First.class, Second.class, Last.class})
public interface Complete {}

public class Book {
    @NotEmpty(groups=First.class)
    private String title;

    @Size(max=30, groups=Second.class)
    private String subtitle;

    @Valid
    @NotNull(groups=First.class)
    private Author author;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getSubtitle() {
        return subtitle;
    }

    public void setSubtitle(String subtitle) {
        this.subtitle = subtitle;
    }

    public Author getAuthor() {
        return author;
    }

    public void setAuthor(Author author) {
        this.author = author;
    }
}

public class Author {
    @NotEmpty(groups=Last.class)
    private String firstName;
    
    @NotEmpty(groups=First.class)
    private String lastName;

    @Size(max=30, groups=Last.class)
    private String company;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }
}

Assuming the validation of the Complete group on the following book instance:

Author author = new Author();
author.setLastName( "Baudelaire" );
author.setFirstName( "" );
Book book = new Book();
book.setAuthor( author );

the validation routine will return the following failure:

  • @NotNull failure (from @NotEmpty) on the title field

As both title and author.lastname are checked as part of the First group. If the instance is updated:

book.setTitle( "Les fleurs du mal" );
author.setCompany("Some random publisher with a very very very long name");

the validation routine will return the following failures:

  • author.firstName fails to pass the @Size(min=1) (from @NotEmpty) constraint

  • author.company fails to pass the @Size constraint

As the First and Second groups pass without failure, the Last group is going through validation.

Chapter 5. Validation APIs

The default package for the Bean Validation APIs is javax.validation.

5.1. Validator API

The main Bean Validation API is the javax.validation.Validator interface.

A Validator instance is able to validate instances of beans and their associated objects if any. It is recommended to leave the caching of Validator instances to the ValidatorFactory. Validator implementations must be thread-safe.

Example 5.1. Validator interface

/**
 * Validates bean instances. Implementations of this interface must be thread-safe.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 * @author Gunnar Morling
 */
public interface Validator {

    /**
     * Validates all constraints on {@code object}.
     *
     * @param object object to validate
     * @param groups the group or list of groups targeted for validation (defaults to
     *        {@link Default})
     * @return constraint violations or an empty set if none
     * @throws IllegalArgumentException if object is {@code null}
     *         or if {@code null} is passed to the varargs groups
     * @throws ValidationException if a non recoverable error happens
     *         during the validation process
     */
    <T> Set<ConstraintViolation<T>> validate(T object, Class<?>... groups);

    /**
     * Validates all constraints placed on the property of {@code object}
     * named {@code propertyName}.
     *
     * @param object object to validate
     * @param propertyName property to validate (i.e. field and getter constraints)
     * @param groups the group or list of groups targeted for validation (defaults to
     *        {@link Default})
     * @return constraint violations or an empty set if none
     * @throws IllegalArgumentException if {@code object} is {@code null},
     *         if {@code propertyName} is {@code null}, empty or not a valid object property
     *         or if {@code null} is passed to the varargs groups
     * @throws ValidationException if a non recoverable error happens
     *         during the validation process
     */
    <T> Set<ConstraintViolation<T>> validateProperty(T object,
                                                     String propertyName,
                                                     Class<?>... groups);

    /**
     * Validates all constraints placed on the property named {@code propertyName}
     * of the class {@code beanType} would the property value be {@code value}.
     * <p/>
     * {@link ConstraintViolation} objects return {@code null} for
     * {@link ConstraintViolation#getRootBean()} and {@link ConstraintViolation#getLeafBean()}.
     *
     * @param beanType the bean type
     * @param propertyName property to validate
     * @param value property value to validate
     * @param groups the group or list of groups targeted for validation (defaults to
     *        {@link Default}).
     * @return constraint violations or an empty set if none
     * @throws IllegalArgumentException if {@code beanType} is {@code null},
     *         if {@code propertyName} is {@code null}, empty or not a valid object property
     *         or if {@code null} is passed to the varargs groups
     * @throws ValidationException if a non recoverable error happens
     *         during the validation process
     */
    <T> Set<ConstraintViolation<T>> validateValue(Class<T> beanType,
                                                  String propertyName,
                                                  Object value,
                                                  Class<?>... groups);

    /**
     * Returns the descriptor object describing bean constraints.
     * <p/>
     * The returned object (and associated objects including
     * {@link ConstraintDescriptor}s) are immutable.
     *
     * @param clazz class or interface type evaluated
     * @return the bean descriptor for the specified class
     * @throws IllegalArgumentException if clazz is {@code null}
     * @throws ValidationException if a non recoverable error happens
     *         during the metadata discovery or if some
     *         constraints are invalid.
     */
    BeanDescriptor getConstraintsForClass(Class<?> clazz);

    /**
     * Returns an instance of the specified type allowing access to
     * provider-specific APIs.
     * <p/>
     * If the Bean Validation provider implementation does not support
     * the specified class, {@link ValidationException} is thrown.
     *
     * @param type the class of the object to be returned
     * @return an instance of the specified class
     * @throws ValidationException if the provider does not support the call
     */
    <T> T unwrap(Class<T> type);

    /**
     * Returns the contract for validating parameters and return values of methods
     * and constructors.
     *
     * @return contract for method and constructor validation
     *
     * @since 1.1
     */
    ExecutableValidator forExecutables();
}

The methods validate(), validateProperty() and validateValue() are used for the validation of Java beans respectively single bean properties. See the next section for more details.

forExecutables() provides access to the contract for validating method and constructor parameters and return values. The individual methods for method and constructor validation are described in Section 5.1.2, “Methods for validating method and constructor constraints”.

getConstraintsForClass() returns constraint-related metadata for given types and is described in detail in Chapter 6, Constraint metadata request APIs.

unwrap() is provided as a way to access objects of a given type specific to a Bean Validation provider typically as a complement to the Validator contract. Using this method makes your code non portable.

Example 5.2. Using unwrap to access a provider specific contract

//if using the ACME provider
ACMEValidator acmeValidator = factory.unwrap(ACMEValidator.class);
acmeValidator.setSpecificConfiguration( [...] );

5.1.1. Validation methods

<T> Set<ConstraintViolation<T>> validate(T object, Class<?>... groups) is used to validate a given object. This method implements the logic described in Section 4.6, “Validation routine”. An IllegalArgumentException is thrown when null is passed for the object parameter or the varargs groups parameter. A Set containing all ConstraintViolation objects representing the failing constraints is returned, an empty Set is returned otherwise.

<T> Set<ConstraintViolation<T>> validateProperty(T object, String propertyName, Class<?>... groups) validates a given field or property of an object. An IllegalArgumentException is thrown when validateProperty() is called and object is null or propertyName is null empty or invalid or null is passed to the varargs groups parameter. The property name is the JavaBeans property name (as defined by the JavaBeans Introspector class). This method implements the logic described in Section 4.6, “Validation routine” but only to the given property. @Valid is not honored by this method. This method is useful for partial object validation.

<T> Set<ConstraintViolation<T>> validateValue(Class<T> beanType, String propertyName, Object value, Class<?>... groups) validates the property referenced by propertyName present on beanType or any of its superclasses, if the property value were value. An IllegalArgumentException is thrown when validateValue() is called and object is null or propertyName is null empty or invalid or null is passed to the varargs groups parameter. This method implements the logic described in Section 4.6, “Validation routine” and apply it only to the given property and for the given value. @Valid is not honored by this method. This method is useful for ahead of time validation (i.e. before the JavaBean is populated or updated).

Note

If multiple constrained fields or getters share the same name and hide one another in the class hierarchy according to the Java visibility rules, the list of constraints evaluated is unspecified. This will be clarified in a later version of this specification. Note that method overriding is not impacted.

If getters and fields share the same name and are present at different levels of the hierarchy, the list of constraints evaluated is unspecified. This will be clarified in a later version of this specification.

However, constraints hosted on the most specific (hierarchy wise) element type are always evaluated.

Note

validateProperty() and validateValue() accept property names and not full paths. Bean Validation implementations might accept string representations of paths but this behavior is not portable.

If some unrecoverable failure happens during validation, a ValidationException is raised. This exception can be specialized in some situations (invalid group definition, invalid constraint definition, invalid constraint declaration). See Chapter 9, Exception model or the relative sections for more information.

5.1.1.1. Examples

All the examples will be based on the following class definition, constraint declarations and address instance.

public class Address {
    @NotNull @Size(max=30)
    private String addressline1;

    @Size(max=30)
    private String addressline2;

    private String zipCode;

    private String city;

    public String getAddressline1() {
        return addressline1;
    }

    public void setAddressline1(String addressline1) {
        this.addressline1 = addressline1;
    }

    public String getAddressline2() {
        return addressline2;
    }

    public void setAddressline2(String addressline2) {
        this.addressline2 = addressline2;
    }

    public String getZipCode() {
        return zipCode;
    }

    public void setZipCode(String zipCode) {
        this.zipCode = zipCode;
    }

    @Size(max=30) @NotNull
    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }
}

Address address = new Address();
address.setAddressline1( null );
address.setAddressline2( null );
address.setCity("Llanfairpwllgwyngyllgogerychwyrndrobwyll-llantysiliogogogoch");
//town in North Wales

The following code will return two ConstraintViolation objects. One for addressline1 violating @NotNull and one for city violating @Size.

validator.validate(address).size() == 2

The following code will return one ConstraintViolation since city violates @Size and only city is validated.

validator.validateProperty(address, "city").size() == 1

The following code will return no ConstraintViolation object because the value "Paris" for city would not raise any constraint failure.

validator.validateValue("city", "Paris").size() == 0

5.1.2. Methods for validating method and constructor constraints

The methods for the validation of parameters and return values of methods and constructors can be found on the interface javax.validation.executable.ExecutableValidator.

Example 5.3. ExecutableValidator interface

package javax.validation.executable;

/**
 * Validates parameters and return values of methods and constructors.
 * Implementations of this interface must be thread-safe.
 *
 * @author Gunnar Morling
 * @since 1.1
 */
public interface ExecutableValidator {

    /**
     * Validates all constraints placed on the parameters of the given method.
     *
     * @param <T> the type hosting the method to validate
     * @param object the object on which the method to validate is invoked
     * @param method the method for which the parameter constraints is validated
     * @param parameterValues the values provided by the caller for the given method's
     *        parameters
     * @param groups the group or list of groups targeted for validation (defaults to
     *        {@link Default})
     * @return a set with the constraint violations caused by this validation;
     *         will be empty if no error occurs, but never {@code null}
     * @throws IllegalArgumentException if {@code null} is passed for any of the parameters
     *         or if parameters don't match with each other
     * @throws ValidationException if a non recoverable error happens during the
     *         validation process
     */
    <T> Set<ConstraintViolation<T>> validateParameters(T object,
                                                       Method method,
                                                       Object[] parameterValues,
                                                       Class<?>... groups);

    /**
     * Validates all return value constraints of the given method.
     *
     * @param <T> the type hosting the method to validate
     * @param object the object on which the method to validate is invoked
     * @param method the method for which the return value constraints is validated
     * @param returnValue the value returned by the given method
     * @param groups the group or list of groups targeted for validation (defaults to
     *        {@link Default})
     * @return a set with the constraint violations caused by this validation;
     *         will be empty if no error occurs, but never {@code null}
     * @throws IllegalArgumentException if {@code null} is passed for any of the object,
     *         method or groups parameters or if parameters don't match with each other
     * @throws ValidationException if a non recoverable error happens during the
     *         validation process
     */
    <T> Set<ConstraintViolation<T>> validateReturnValue(T object,
                                                        Method method,
                                                        Object returnValue,
                                                        Class<?>... groups);

    /**
     * Validates all constraints placed on the parameters of the given constructor.
     *
     * @param <T> the type hosting the constructor to validate
     * @param constructor the constructor for which the parameter constraints is validated
     * @param parameterValues the values provided by the caller for the given constructor's
     *        parameters
     * @param groups the group or list of groups targeted for validation (defaults to
     *        {@link Default})
     * @return a set with the constraint violations caused by this validation;
     *         Will be empty if no error occurs, but never {@code null}
     * @throws IllegalArgumentException if {@code null} is passed for any of the parameters
     *         or if parameters don't match with each other
     * @throws ValidationException if a non recoverable error happens during the
     *         validation process
     */
    <T> Set<ConstraintViolation<T>> validateConstructorParameters(Constructor<? extends T> constructor,
                                                                  Object[] parameterValues,
                                                                  Class<?>... groups);

    /**
     * Validates all return value constraints of the given constructor.
     *
     * @param <T> the type hosting the constructor to validate
     * @param constructor the constructor for which the return value constraints is validated
     * @param createdObject the object instantiated by the given method
     * @param groups the group or list of groups targeted for validation (defaults to
     *        {@link Default})
     * @return a set with the constraint violations caused by this validation;
     *         will be empty, if no error occurs, but never {@code null}
     * @throws IllegalArgumentException if {@code null} is passed for any of the parameters
     *         or if parameters don't match with each other
     * @throws ValidationException if a non recoverable error happens during the
     *         validation process
     */
    <T> Set<ConstraintViolation<T>> validateConstructorReturnValue(Constructor<? extends T> constructor,
                                                                   T createdObject,
                                                                   Class<?>... groups);
}

<T> Set<ConstraintViolation<T>> validateParameters(T object, Method method, Object[] parameterValues, Class<?>... groups) validates the arguments (as given in parameterValues) for the parameters of a given method (identified by method). Cross-parameter constraints are also validated. A set containing all ConstraintViolation objects representing the failing constraints is returned, an empty set is returned if no constraint violation occurred. An IllegalArgumentException will be thrown if null is passed for any of the parameters or if the parameters don't match with each other (i.e. object and method don't match, parameterValues and method don't match).

<T> Set<ConstraintViolation<T>> validateReturnValue(T object, Method method, Object returnValue, Class<?>... groups) validates the return value (specified by returnValue) of a given method (identified by method). A set containing all ConstraintViolation objects representing the failing constraints is returned, an empty set is returned if no constraint violation occurred. An IllegalArgumentException will be thrown if null is passed for any of the parameters object, method and groups or if the parameters don't match with each other (i.e. object and method don't match, returnValue and method don't match).

<T> Set<ConstraintViolation<T>> validateConstructorParameters(Constructor<T> constructor, Object[] parameterValues, Class<?>... groups) validates the arguments (as given in parameterValues) for the parameters of a given constructor (identified by constructor). Cross-parameter constraints are also validated. A set containing all ConstraintViolation objects representing the failing constraints is returned, an empty set is returned if no constraint violation occurred. An IllegalArgumentException will be thrown if null is passed for any of the parameters or if the parameters don't match with each other (i.e. parameterValues and constructor don't match).

<T> Set<ConstraintViolation<T>> validateConstructorReturnValue(Constructor<T> constructor, T createdObject, Class<?>... groups) validates the object (specified by createdObject) of a given constructor (identified by constructor). A set containing all ConstraintViolation objects representing the failing constraints is returned, an empty set is returned if no constraint violation occurred. An IllegalArgumentException will be thrown if null is passed for any of the parameters or if the parameters don't match with each other (i.e. createdObject and constructor don't match).

None of those methods honor the XML configuration around executable validation nor the presence of @ValidateOnExecution. In other words, elements will be validated regardless of these settings when explicitly calling the validation methods.

5.1.2.1. Examples

All the examples will be based on the following class definitions, constraint declarations and instances.

public class OrderService {

    @NotNull
    private CreditCardProcessor creditCardProcessor;

    @Valid
    public OrderService(@NotNull CreditCardProcessor creditCardProcessor) {
        [...]
    }

    @NotNull
    public Order placeOrder(
        @NotNull @Size(min=3, max=20) String customerCode,
        @NotNull @Valid Item item,
        @Min(1) int quantity) {

        [...]
    }
}

public class Item {

    @NotNull;
    private String name;

    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
}

Item item1 = new Item();
item1.setName("Kiwi");

Item item2 = new Item();
item2.setName(null);

Constructor<OrderService> constructor = [...]; //get constructor object
Method placeOrder = [...]; //get method object

OrderService orderService = new OrderService(new DefaultCreditCardProcessor());

ExecutableValidator executableValidator = Validation
    .buildDefaultValidatorFactory().getValidator().forExecutables();

The following method parameter validation will return one ConstraintViolation object as the customer code is null:

//orderService.placeOrder(null, item1, 1);
executableValidator.validateParameters(
    orderService, placeOrder, new Object[] { null, item1, 1 }).size() == 1;

The following method parameter validation will return one ConstraintViolation object as the item parameter is marked for cascaded validation and the given Item instance is not valid (its name is null):

//orderService.placeOrder("CUST-123", item2, 1);
executableValidator.validateParameters(
    orderService, placeOrder, new Object[] { "CUST-123", item2, 1 }).size() == 1;

The following constructor parameter validation will return one ConstraintViolation object as null is passed for the creditCardProcessor parameter:

//new OrderService(null);
executableValidator.validateConstructorParameters(constructor, new Object[] { null })
    .size() == 1;

Assuming the placeOrder() method returned null, the following return value validation will return one ConstraintViolation:

executableValidator.validateReturnValue(orderService, placeOrder, null).size() == 1;

Assuming the constructor of OrderService failed to store the given credit card processor into the creditCardProcessor, field the following validation of the constructor return value would fail as the constructor is marked with @Valid and the @NotNull constraint of the OrderService class would be violated:

executableValidator.validateConstructorReturnValue(constructor, orderService).size() == 1;

Let's now look at how a validation interceptor would use these methods.

@Interceptor
public class SampleMethodInterceptor {
    @Inject
    private Validator validator;

    @AroundInvoke
    public Object validateMethodInvocation(InvocationContext ctx) throws Exception {
        //validate parameters
        Set<ConstraintViolation<Object>> violations;
        violations = validator.forExecutables().validateParameters(
                ctx.getTarget(),
                ctx.getMethod(),
                ctx.getParameters()
        );

        //if a violation occurs for parameters, raise an exception
        if ( !violations.isEmpty() ) {
            throw new ConstraintViolationException(
                    buildMessage( ctx.getMethod(), ctx.getParameters(), violations ),
                    violations
            );
        }

        //execute the method proper
        Object result = ctx.proceed();

        //validate the return type
        violations = validator.forExecutables().validateReturnValue(
                ctx.getTarget(),
                ctx.getMethod(),
                result
        );

        //if a violation occurs for the return type, raise an exception
        if ( !violations.isEmpty() ) {
            throw new ConstraintViolationException(
                    buildMessage( ctx.getMethod(), ctx.getParameters(), violations ),
                    violations
            );
        }

        //return the result
        return result;
    }
}

5.1.3. groups

Groups allow you to restrict the set of constraints applied during validation. Groups targeted are passed as parameters to the validate(), validateProperty() and validateValue() methods as well as the methods to validate method/constructor constraints (see Section 5.1.2, “Methods for validating method and constructor constraints”). All constraints belonging to the targeted group(s) are applied during the Section 4.6, “Validation routine”. If no group is passed, the Default group is assumed. Section 3.1.1.2, “groups” describes how to define groups on constraints.

When more than one group is evaluated and passed to the various validate methods, order is not constrained. It is equivalent to the validation of a group G inheriting all groups (i.e. implementing all interfaces) passed to the validation method.

5.1.3.1. Examples

/** Validates a minimal set of constraints */
public interface Minimal {}

public class Address {

    @NotEmpty(groups = Minimal.class)
    @Size(max=50)
    private String street1;
    
    @NotEmpty
    private String city;

    @NotEmpty(groups = {Minimal.class, Default.class})
    private String zipCode;

    [...]
}

In the previous example, @NotEmpty (and it's composing constraints) on street1 applies to the group Minimal, @Size on street1 applies to the group Default and @NotEmpty (and it's composing constraints) on zipCode applies to the groups Default and Minimal.

validator.validate(address);

validates the group Default (implicitly) and applies @Size on street1, @NotEmpty (and its composing constraints) on city, @NotEmpty (and its composing constraints) on zipCode. Particularly, @NotEmpty (and its composing constraints) on street1 are not applied.

validator.validate(address, Minimal.class);

applies @NotEmpty (and its composing constraints) on street1 and @NotEmpty (and its composing constraints) on zipCode because they belong to the Minimal group.

validator.validate(address, Minimal.class, Default.class);

validates both Default and Minimal groups. The routine applies @NotEmpty (and its composing constraints) and @Size on street1, @NotEmpty (and its composing constraints) on city, @NotEmpty (and its composing constraints) on zipCode. Note that if zipCode is empty, only one ConstraintViolation object will represent the failure and the not empty validation will only be executed once.

Let's look at a more complex example involving group sequence.

public class Address {
    @NotEmpty(groups = Minimal.class)
    @Size(max=50, groups=FirstStep.class)
    private String street1;
    
    @NotEmpty(groups=SecondStep.class)
    private String city;

    @NotEmpty(groups = {Minimal.class, SecondStep.class})
    private String zipCode;

    [...]

    public interface FirstStep {}

    public interface SecondStep {}
    
    @GroupSequence({Firststep.class, SecondStep.class})
    public interface Total {}
}

When running:

validator.validate(address, Minimal.class, Total.class);

the validation process will process @NotEmpty (and it's composing constraints) and @Size from street1 and @NotEmpty (and it's composing constraints) from zipCode. If @Size from street1 does not generate a failure, then @NotEmpty (and it's composing constraints) from city will be processed as part of SecondStep. Note that @NotEmpty (and it's composing constraints) from zipCode are not reprocessed as they have already been processed before.

When running:

validator.validate(address, Total.class, SecondStep.class);

@NotEmpty (and it's composing constraints) from city and @NotEmpty (and it's composing constraints) from zipCode will be processed even if @Size from street1 fails: while SecondStep is in the Total group sequence and hence should not be triggered if FirstStep has a failure, it also has been requested outside the sequence (in this case explicitly).

Note

If the group definition is invalid, a GroupDefinitionException is raised.

5.2. ConstraintViolation

ConstraintViolation is the class describing a single constraint failure. A set of ConstraintViolation is returned for an object validation.

/**
 * Describes a constraint violation. This object exposes the constraint
 * violation context as well as the message describing the violation.
 *
 * @author Emmanuel Bernard
 */
public interface ConstraintViolation<T> {

    /**
     * @return the interpolated error message for this constraint violation
     */
    String getMessage();

    /**
     * @return the non-interpolated error message for this constraint violation
     */
    String getMessageTemplate();

    /**
     * Returns the root bean being validated. For method validation, returns
     * the object the method is executed on.
     * <p/>
     * Returns {@code null} when:
     * <ul>
     *     <li>the {@code ConstraintViolation} is returned after calling
     *     {@link Validator#validateValue(Class, String, Object, Class[])}</li>
     *     <li>the {@code ConstraintViolation} is returned after validating a
     *     constructor.</li>
     * </ul>
     *
     * @return the validated object, the object hosting the validated element or {@code null}
     */
    T getRootBean();

    /**
     * Returns the class of the root bean being validated.
     * For method validation, this is the object class the
     * method is executed on.
     * For constructor validation, this is the class the constructor
     * is declared on.
     *
     * @return the class of the root bean or of the object hosting the validated element
     */
    Class<T> getRootBeanClass();

    /**
     * Returns:
     * <ul>
     *     <li>the bean instance the constraint is applied on if it is
     *     a bean constraint</li>
     *     <li>the bean instance hosting the property the constraint
     *     is applied on if it is a property constraint</li>
     *     <li>{@code null} when the {@code ConstraintViolation} is returned
     *     after calling {@link Validator#validateValue(Class, String, Object, Class[])}
     *     </li>
     *     <li>the object the method is executed on if it is
     *     a method parameter, cross-parameter or return value constraint</li>
     *     <li>{@code null} if it is a constructor parameter or
     *     cross-parameter constraint</li>
     *     <li>the object the constructor has created if it is a
     *     constructor return value constraint</li>
     * </ul>
     *
     * @return the leaf bean
     */
    Object getLeafBean();

    /**
     * Returns an {@code Object[]} representing the constructor or method invocation
     * arguments if the {@code ConstraintViolation} is returned after validating the
     * method or constructor parameters.
     * Returns {@code null} otherwise.
     *
     * @return parameters of the method or constructor invocation or {@code null}
     *
     * @since 1.1
     */
    Object[] getExecutableParameters();

    /**
     * Returns the return value of the constructor or method invocation
     * if the {@code ConstraintViolation} is returned after validating the method
     * or constructor return value.
     * <p/>
     * Returns {@code null} if the method has no return value.
     * Returns {@code null} otherwise.
     *
     * @return the method or constructor return value or {@code null}
     *
     * @since 1.1
     */
    Object getExecutableReturnValue();

    /**
     * @return the property path to the value from {@code rootBean}
     */
    Path getPropertyPath();

    /**
     * Returns the value failing to pass the constraint.
     * For cross-parameter constraints, an {@code Object[]} representing
     * the method invocation arguments is returned.
     *
     * @return the value failing to pass the constraint
     */
    Object getInvalidValue();

    /**
     * Returns the constraint metadata reported to fail.
     * The returned instance is immutable.
     *
     * @return constraint metadata
     */
    ConstraintDescriptor<?> getConstraintDescriptor();

    /**
     * Returns an instance of the specified type allowing access to
     * provider-specific APIs. If the Bean Validation provider
     * implementation does not support the specified class,
     * {@link ValidationException} is thrown.
     *
     * @param type the class of the object to be returned
     * @return an instance of the specified class
     * @throws ValidationException if the provider does not support the call
     *
     * @since 1.1
     */
    <U> U unwrap(Class<U> type);
}

The getMessage() method returns the interpolated (localized) message for the failing constraint (see Section 5.3, “Message interpolation” for more information on message interpolator). This can be used by clients to expose user friendly messages.

The getMessageTemplate() method returns the non-interpolated error message (usually the message attribute on the constraint declaration). Frameworks can use this as an error code key.

The getRootBean() method returns the root object being validated that led to the failing constraint (i.e. the object the client code passes to the Validator.validate() method). For method validation, returns the object the method is executed on. For constructors or when Validator.validateValue() is used, returns null.

The getRootBeanClass() method returns the class of the root bean being validated. For method validation, this is the object class the method is executed on. For constructor validation, this is the class the constructor is declared on.

The getLeafBean() method returns the following object:

  • If a bean constraint, the bean instance the constraint is applied on.

  • If a property constraint, the bean instance hosting the property the constraint is applied on.

  • If a property constraint, null when the ConstraintViolation is returned after calling Validator.validateValue().

  • If a method parameter, cross-parameter or return value constraint, the object the method is executed on.

  • If a constructor parameter or cross-parameter constraint, null.

  • If a constructor return value constraint, the object the constructor has created.

The getExecutableParameters() returns the parameters provided to the method or constructor invocation or null if not validating the method or constructor parameters.

The getExecutableReturnValue() returns the return value of the method or constructor invocation or null if the method has no return value or if not validating the method or constructor return value.

The getInvalidValue() method returns the value (field, property, method/constructor parameter, method/constructor return value or validated object) being passed to isValid(). For a cross-parameter constraint failure, an Object[] representing the method/constructor invocation arguments is returned.

getConstraintDescriptor() provides access to the failing constraint metadata (see Section 6.11, “ConstraintDescriptor”).

The getPropertyPath() method returns the Path object representing the navigation path from the root object to the failing object.

unwrap() is provided as a way to access objects of a given type specific to a Bean Validation provider typically as a complement to the ConstraintViolation contract. Using this method makes your code non portable.

Example 5.4. Path, Node and ElementKind interfaces

/**
 * Represents the navigation path from an object to another
 * in an object graph.
 * Each path element is represented by a {@code Node}.
 * <p/>
 * The path corresponds to the succession of nodes
 * in the order they are returned by the {@code Iterator}.
 *
 * @author Emmanuel Bernard
 * @author Gunnar Morling
 */
public interface Path extends Iterable<Path.Node> {

    /**
     * Represents an element of a navigation path.
     */
    interface Node {

        /**
         * Returns the name of the element which the node represents:
         * <ul>
         *     <li>{@code null} if it is a leaf node which represents an entity / bean.
         *     In particular, the node representing the root object.</li>
         *     <li>The property name for a property.</li>
         *     <li>The method name for a method.</li>
         *     <li>The unqualified name of the type declaring the constructor
         *     for a constructor.</li>
         *     <li>The parameter named as defined by the {@link ParameterNameProvider}
         *     for a method or constructor parameter.</li>
         *     <li>The literal {@code <cross-parameter>} for a method or constructor
         *     cross-parameter.</li>
         *     <li>The literal {@code <return value>} for a method or constructor return
         *     value.</li>
         * </ul>
         *
         * @return name of the element which the node represents
         */
        String getName();

        /**
         * @return {@code true} if the node represents an object contained in an
         *         {@code Iterable} or in a {@code Map}, {@code false} otherwise
         */
        boolean isInIterable();

        /**
         * @return the index the node is placed in if contained in an array or
         *         {@code List}; {@code null} otherwise
         */
        Integer getIndex();

        /**
         * @return the key the node is placed in if contained in a {@code Map},
         *         {@code null} otherwise
         */
        Object getKey();

        /**
         * The kind of element represented by the node. The following relationship
         * between an {@link ElementKind} and its {@code Node} subtype exists:
         * <ul>
         *     <li>{@link ElementKind#BEAN}: {@link BeanNode}</li>
         *     <li>{@link ElementKind#PROPERTY}: {@link PropertyNode}</li>
         *     <li>{@link ElementKind#METHOD}: {@link MethodNode}</li>
         *     <li>{@link ElementKind#CONSTRUCTOR}: {@link ConstructorNode}</li>
         *     <li>{@link ElementKind#PARAMETER}: {@link ParameterNode}</li>
         *     <li>{@link ElementKind#CROSS_PARAMETER}: {@link CrossParameterNode}</li>
         *     <li>{@link ElementKind#RETURN_VALUE}: {@link ReturnValueNode}</li>
         * </ul>
         * <p/>
         * This is useful to narrow down the {@code Node} type and access node specific
         * information:
         * <pre>
         * switch(node.getKind() {
         * case METHOD:
         *     name = node.getName();
         *     params = node.as(MethodNode.class).getParameterTypes();
         * case PARAMETER:
         *     index = node.as(ParameterNode.class).getParameterIndex();
         * [...]
         * }
         * </pre>
         *  @return the {@code ElementKind}
         *
         * @since 1.1
         */
        ElementKind getKind();

        /**
         * Narrows the type of this node down to the given type. The appropriate
         * type should be checked before by calling {@link #getKind()}.
         *
         * @param <T> the type to narrow down to
         * @param nodeType class object representing the descriptor type to narrow down to
         *                 to
         *
         * @return this node narrowed down to the given type.
         *
         * @throws ClassCastException If this node is not assignable to the type {@code T}
         * @since 1.1
         */
        <T extends Node> T as(Class<T> nodeType);
    }

    /**
     * Node representing a method.
     *
     * @since 1.1
     */
    interface MethodNode extends Node {

        /**
         * @return the list of parameter types
         */
        List<Class<?>> getParameterTypes();
    }

    /**
     * Node representing a constructor.
     *
     * @since 1.1
     */
    interface ConstructorNode extends Node {

        /**
         * @return the list of parameter types
         */
        List<Class<?>> getParameterTypes();
    }

    /**
     * Node representing the return value of a method or constructor.
     *
     * @since 1.1
     */
    interface ReturnValueNode extends Node {
    }

    /**
     * Node representing a parameter of a method or constructor.
     *
     * @since 1.1
     */
    interface ParameterNode extends Node {

        /**
         * @return the parameter index in the method or constructor definition
         */
        int getParameterIndex();
    }

    /**
     * Node representing the element holding cross-parameter constraints
     * of a method or constructor.
     *
     * @since 1.1
     */
    interface CrossParameterNode extends Node {
    }

    /**
     * Node representing a bean.
     *
     * @since 1.1
     */
    interface BeanNode extends Node {
    }

    /**
     * Node representing a property.
     *
     * @since 1.1
     */
    interface PropertyNode extends Node {
    }
}
/**
 * Enum of possible kinds of elements encountered in Bean Validation.
 * <p/>
 * Mostly elements that can be constrained and described in the metadata
 * but also elements that can be part of a {@link Path} and represented
 * by a {@link Path.Node}
 *
 * @author Emmanuel Bernard
 * @author Gunnar Morling
 *
 * @since 1.1
 */
public enum ElementKind {
    /**
     * A Java Bean or object.
     */
    BEAN,

    /**
     * A property of a Java Bean.
     */
    PROPERTY,

    /**
     * A method.
     */
    METHOD,

    /**
     * A constructor.
     */
    CONSTRUCTOR,

    /**
     * A parameter of a method or constructor.
     */
    PARAMETER,

    /**
     * Element holding cross-parameter constraints of a method or constructor.
     */
    CROSS_PARAMETER,

    /**
     * The return value of a method or constructor.
     */
    RETURN_VALUE
}

Path is an iterable of Node objects. Node offers the following methods:

  • getName() returns the name of the element which the node represents:

    • null if it is a leaf node which represents an entity / bean. In particular, the node representing the root object.

    • The property name for a property.

    • The method name for a method.

    • The unqualified name of the type declaring the constructor for a constructor.

    • The parameter named as defined by the ParameterNameProvider (see Section 4.5.2.2, “Naming parameters”) for a method or constructor parameter.

    • The literal <cross-parameter> for a method or constructor cross-parameter.

    • The literal <return value> for a method or constructor return value.

  • isInIterable() returns true if the node represents an object contained in an Iterable or in a Map, false otherwise.

  • getIndex() returns the index of the node if it is contained in an array or List. Returns null otherwise.

  • getKey() returns the key of the node if it is contained in a Map. Returns null otherwise.

  • getKind() returns the ElementKind corresponding to the actual node type. This can be used in conjunction with the method as() to narrow the type and access node specific methods

  • as(Class<? extends Node>) returns the node instance narrowed to the type passed as a parameter or ClassCastException if the type and node don't match.

Nodes are of the following possible types:

  • BeanNode

  • PropertyNode

  • MethodNode

  • ConstructorNode

  • ParameterNode

  • CrossParameterNode

  • ReturnValueNode

It is possible to narrow a node instance to its precise type and extract node specific information by the use of Node.getKind() and Node.as(Class<? extends Node>). In particular, MethodNode and ConstructorNode host getParameterTypes() which return the method or constructor parameter list. Likewise ParameterNode hosts getParameterIndex() which returns the parameter index in the method or constructor parameter list.

Example 5.5. Narrow a node to its specific type

Node node = [...];
switch ( node.getKind() ) {
case METHOD:
    MethodNode methodNode = node.as(MethodNode.class);
    methodName = methodNode.getName();
    params = methodNode.getParameterTypes().toArray( 
        new Class<?>[methodNode.getParameterTypes().size()] );
    break;
case CONSTRUCTOR:
    ConstructorNode constructorNode = node.as(ConstructorNode.class);
    methodName = constructorNode.getName();
    params = constructorNode.getParameterTypes().toArray( 
        new Class<?>[constructorNode.getParameterTypes().size()] );
    break;
case PARAMETER:
    arg = node.as(ParameterNode.class).getParameterIndex();
    break;
case CROSS_PARAMETER:
    [...]
case RETURN_VALUE:
    [...]
case PARAMETER:
    [...]
case BEAN:
    [...]
case PROPERTY:
    [...]
}

Path objects are built according to the following rules:

  • The runtime type is considered, not the static type. For example if a property is declared Collection<String> but its runtime type is ArrayList<String>, the property is considered an ArrayList<String>.

  • If the failing object is the root object, a BeanNode with name set to null is added to the Path. The ElementKind of the node is ElementKind.BEAN.

  • When an association is traversed:

    • a PropertyNode object whose name equals the name of the association property (field name or Java Bean property name) is added to Path. The ElementKind of the node is ElementKind.PROPERTY.

    • if the association is a List or an array, the following Node object added contains the index value in getIndex().

    • if the association is a Map, the following Node object added (representing a given map entry) contains the key value in getKey()

    • for all Iterable or Map, the following Node object added is marked as inIterable (isInIterable())

  • For a property level constraint (field and getter)

    • a PropertyNode object is added to Path whose name equals the name of the property (field name or Java Bean property name). The ElementKind of the is ElementKind.PROPERTY.

    • the property path is considered complete

    • a PropertyNode object is added to Path whose name equals the name of the property (field name or Java Bean property name). The ElementKind of the is ElementKind.PROPERTY.

    • the property path is considered complete

  • For a class level constraint:

    • a BeanNode object is added to Path whose name is null. The ElementKind of the node is ElementKind.BEAN.

    • the property path is considered complete

  • For a method/constructor constraint (parameter, cross-parameter or return value constraint on a method or constructor):

    • a MethodNode respectively a ConstructorNode object is added to the Path which represents the validated method respectively constructor. The name of the node equals the validated method name or the validated constructor's unqualified class name, the ElementKind of the node is ElementKind.METHOD respectively ElementKind.CONSTRUCTOR.

    • if the constraint is on a parameter, a ParameterNode object is added to the Path which represents the validated parameter. The name of the node equals the parameter name as determined by the current parameter name provider (see Section 4.5.2.2, “Naming parameters”). The ElementKind of the node is elementKind.PARAMETER.

    • if the constraint is a cross-parameter constraint, a CrossParameterNode object is added to the Path which represents the validated cross-parameter element. The name of the node has the constant value <cross-parameter>. The ElementKind of the node is ElementKind.CROSS_PARAMETER.

    • if the constraint is on the return value, a ReturnValueNode object is added to the Path which represents the validated return value. The name of the node has the constant value <return value>. The ElementKind of the node is ElementKind.RETURN_VALUE.

    • the property path is considered complete

  • If a parameter or the return value of a method or constructor is traversed:

    • a MethodNode respectively ConstructorNode object is added to the Path which represents the concerned method respectively constructor. The name of the node equals the concerned method name or the constructor's unqualified class name, the ElementKind of the node is ElementKind.METHOD or ElementKind.CONSTRUCTOR, respectively.

    • if a parameter is traversed, a ParameterNode object is added to the Path which represents the traversed parameter. The name of the node equals the parameter name as determined by the current parameter name provider. The ElementKind of the node is ElementKind.PARAMETER.

    • if a return value is traversed, a ReturnValueNode object is added to the Path which represents the traversed return value. The name of the node has the constant value <return value>. The ElementKind of the node is ElementKind.RETURN_VALUE.

    • if the parameter/return value is a List or an array, the following Node object added contains the index value in getIndex().

    • if the parameter/return value is a Map, the following Node object added (representing a given map entry) contains the key value in getKey().

    • for all Iterable or Map, the following Node object added is marked as inIterable (isInIterable()).

If additional path nodes are added in a constraint validator implementation using the node builder API (see Section 3.4, “Constraint validation implementation”), the following rules apply:

  • if the default path ends with a BeanNode, this node is removed and the first added node (a PropertyNode) inherits its inIterable, key and index values. inIterable, key and index value must not be specified directly on this first node by the user.

  • if the default path ends with a CrossParameterNode, this node is removed.

  • then the additional nodes are appended to the (possibly amended) path generated by the Bean Validation engine as previously described:

    • A PropertyNode is appended in case addPropertyNode(String) is invoked. The node name is equal to the name provided. The ElementKind of the node is ElementKind.PROPERTY.

    • A BeanNode is appended in case addBeanNode() is invoked. The node name is null. The ElementKind of the node is ElementKind.BEAN.

    • A ParameterNode is appended in case addParameterNode(int) is invoked. The node name is equal to the parameter name at the provided index. The name is determined by the current parameter name provider. The ElementKind of the node is ElementKind.PARAMETER. The previous node (removed) must be a CrossParameterNode.

    • if inIterable() is invoked, the node returns true for isInIterable(), false otherwise.

    • if atIndex(Integer) is invoked, the node returns the provided integer for getIndex(), null otherwise.

    • if atKey(Object) is invoked, the node returns the provided object for getKey(), null otherwise.

Note

A given Node object derives its inIterable, key and index properties from the previous association, method parameter or return value traversed.

Note

From getRootBean(), getPropertyPath(), getExecutableParameters() and getExecutableReturnValue(), it is possible to rebuild the context of the failure.

Note

ConstraintViolations occurred during standard bean validation can be distinguished from violations occurred during method/constructor validation by analyzing the ElementKind of the Node of the first node in the violation's property path. In case of constructor or method validation, that ElementKind will be either CONSTRUCTOR or METHOD.

Let there be the following object definitions:

Example 5.6. Object model definition for examples

@SecurityChecking
public class Author {
    private String firstName;
    
    @NotEmpty(message="lastname must not be null")
    private String lastName;

    @Size(max=30)
    private String company;

    [...]

    @OldAndNewPasswordsDifferent @NewPasswordsIdentical
    public void renewPassword(String oldPassword, String newPassword, String retypedNewPassword);
}

@AvailableInStore(groups={Availability.class})
public class Book {
    @NotEmpty(groups={FirstLevelCheck.class, Default.class})
    private String title;

    @Valid
    @NotNull
    private List<Author> authors;

    @Valid
    private Map<String, Review> reviewsPerSource;

    @Valid
    private Review pickedReview;

    [...]
}

public class Review {
    @Min(0) private int rating;
    [...]
}

public class Library {

    public Library(@NotNull String name, @NotNull String location) {
        [...]
    }

    public void addBook(@NotNull @Valid Book book) {
        [...]
    }

    public void addAllBooks(@NotNull @Valid List<Book> books) {
        [...]
    }

    @NotNull public String getLocation() {
        [...]
    }

    @Valid public Map<Author, Book> getMostPopularBookPerAuthor() {
        [...]
    }
}

Assuming a Book instance gets validated, the property paths to the different constraints would be as described in Table 5.1, “propertyPath examples”:

Table 5.1. propertyPath examples

ConstraintpropertyPath
@AvailableInStore on Book

BeanNode(name=null,inIterable=false, index=null, key=null, kind=ElementKind.BEAN)

@NotEmpty on Book.title

PropertyNode(name=title,inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

@NotNull on Book.authors

PropertyNode(name=authors,inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

@SecurityChecking on the fourth author, Author

PropertyNode(name=authors,inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

BeanNode(name=null,inIterable=true, index=3, key=null, kind=ElementKind.BEAN)

@Size on the fourth author, Author.lastname

PropertyNode(name=authors,inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

PropertyNode(name=lastname,inIterable=true, index=4, key=null, kind=ElementKind.PROPERTY)

@NotEmpty on the first author, Author.company

PropertyNode(name=authors,inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

PropertyNode(name=company,inIterable=true, index=0, key=null, kind=ElementKind.PROPERTY)

@Min on the review associated to Consumer Report, Review.rating

PropertyNode(name=reviewsPerSource,inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

PropertyNode(name=rating,inIterable=true, index=null, key="Consumer Report", kind=ElementKind.PROPERTY)

@Min on the picked review, Review.rating

PropertyNode(name=pickedReview,inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

PropertyNode(name=rating,inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

Assuming the constructor and methods of the Library class are subject to method constraint validation, the following property paths would exist for the different constraints:

Table 5.2. Property path examples for constrained methods or constructors

ConstraintpropertyPath
@NotNull on the location parameter of the constructor

ConstructorNode(name=Library, inIterable=false, index=null, key=null, kind=ElementKind.CONSTRUCTOR, parameterTypes=[String.class,String.class])

ParameterNode(name=arg1, inIterable=false, index=null, key=null, kind=ElementKind.PARAMETER, parameterIndex=1)

@NotNull on the book parameter of the addBook() method

MethodNode(name=addBook, inIterable=false, index=null, key=null, kind=ElementKind.METHOD, parameterTypes=[Book.class])

ParameterNode(name=arg0, inIterable=false, index=null, key=null, kind=ElementKind.PARAMETER, parameterIndex=0)

@NotEmpty on Book.title during validation of addBook()

MethodNode(name=addBook, inIterable=false, index=null, key=null, kind=ElementKind.METHOD, parameterTypes=[Book.class])

ParameterNode(name=arg0, inIterable=false, index=null, key=null, kind=ElementKind.PARAMETER, parameterIndex=0)

PropertyNode(name=title, inIterable=false, index=null, key=null, kind=ElementKind.PROPERTY)

@NotEmpty on fourth book, Book.title during validation of addAllBooks()

MethodNode(name=addAllBooks, inIterable=false, index=null, key=null, kind=ElementKind.METHOD, parameterTypes=[List.class])

ParameterNode(name=arg0, inIterable=false, index=null, key=null, kind=ElementKind.PARAMETER, parameterIndex=0)

PropertyNode(name=title,inIterable=true, index=3, key=null, kind=ElementKind.PROPERTY)

@NotNull on the return value of the getLocation() method

MethodNode(name=getLocation, inIterable=false, index=null, key=null, kind=ElementKind.METHOD, parameterTypes=[])

ReturnValueNode(name=<return value>, inIterable=false, index=null, key=null, kind=ElementKind.RETURN_VALUE)

@NotEmpty on most popular book of author "John Doe", Book.title during validation of getMostPopularBookPerAuthor()

MethodNode(name=getMostPopularBookPerAuthor, inIterable=false, index=null, key=null, kind=ElementKind.METHOD, parameterTypes=[])

ReturnValueNode(name=<return value>, inIterable=false, index=null, key=null, kind=ElementKind.RETURN_VALUE)

PropertyNode(name=title,inIterable=true, index=null, key=Author(firstName=John, lastName=Doe), kind=ElementKind.PROPERTY)

@OldAndNewPasswordsDifferent when executing Author.renewPassword() with oldPassword, newPassword and retypedNewPassword set to "foo". @OldAndNewPasswordsDifferent is a cross-parameter constraint.

MethodNode(name=renewPassword, inIterable=false, index=null, key=null, kind=ElementKind.METHOD, parameterTypes=[String.class, String.class, String.class])

CrossParameterNode(name=<cross-parameter>, inIterable=false, index=null, key=null, kind=ElementKind.CROSS_PARAMETER)

@NewPasswordsIdentical when executing Author.renewPassword() with oldPassword as "foo", newPassword as "bar" and retypedNewPassword as "baz". @NewPasswordsIdentical is a cross-parameter constraint creating a constraint violation on the retypedNewPassword parameter.

MethodNode(name=renewPassword, inIterable=false, index=null, key=null, kind=ElementKind.METHOD, parameterTypes=[String.class, String.class, String.class])

ParameterNode(name=arg2, inIterable=false, index=null, key=null, kind=ElementKind.PARAMETER, parameterIndex=2)

Note

Bean Validation implementations should ensure that a ConstraintViolation implementation is Serializable provided that the root bean, the leaf bean, the invalid value and keys in the Path object are Serializable objects.

If a user wishes to send ConstraintViolation remotely, it should make sure the object graph validated is itself Serializable.

5.2.1. Examples

These examples assume the following definition of @NotEmpty.

package com.acme.constraint;

@Documented
@NotNull
@Size(min=1)
@ReportAsSingleViolation
@Constraint(validatedBy = NotEmpty.NotEmptyValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface NotEmpty {
    String message() default "{com.acme.constraint.NotEmpty.message}"
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        NotEmpty[] value();
    }

    class NotEmptyValidator implements ConstraintValidator<NotEmpty, String> {
        public void initialize(NotEmpty constraintAnnotation) {}

        public boolean isValid(String value, ConstraintValidatorContext context) {
            return true;
        }
    }
}

and the following class definitions

public class Author {
    private String firstName;
    
    @NotEmpty(message="lastname must not be null")
    private String lastName;

    @Size(max=30)
    private String company;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }
}

public class Book {
    @NotEmpty(groups={FirstLevelCheck.class, Default.class})
    private String title;

    @Valid
    @NotNull
    private Author author;

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Author getAuthor() {
        return author;
    }

    public void setAuthor(Author author) {
        this.author = author;
    }
}

Author author = new Author();
author.setCompany("ACME");
Book book = new Book();
book.setTitle("");
book.setAuthor(author);

Set<ConstraintViolation> constraintViolations = validator.validate(book);

ConstraintViolations is a set of size 2. One of the entries represents the failure of @NotEmpty (or more precisely @Size(min=1) a composing constraint of @NotEmpty) on the title property.

The ConstraintViolation object for this failure passes the following assertions:

Example 5.7. Test assertions on ContraintViolation

//assuming an english locale, the interpolated message is returned
assert "may not be null or empty".equals( constraintViolation.getMessage() );
assert book == constraintViolation.getRootBean();
assert book == constraintViolation.getLeafBean();

//the offending value
assert book.getTitle().equals( constraintViolation.getInvalidValue() );

//the offending property
Iterator<Node> nodeIter = constraintViolation.getPropertyPath().iterator();
Node node = nodeIter.next();
assert "title".equals( node.getName() );
assert ElementKind.PROPERTY.equals( node.getKind() );

assert false == nodeIter.hasNext();

The second failure, @NotEmpty (or more precisely @NotNull a composing constraint of @NotEmpty) on the author's lastname, will produce the ConstraintViolation object satisfying the following assertions:

assert "lastname must not be null".equals( constraintViolation.getMessage() );
assert book == constraintViolation.getRootBean();
assert author == constraintViolation.getLeafBean();

//the offending value
assert book.getAuthor().getLastName() == constraintViolation.getInvalidValue();

//the offending property
Iterator<Node> nodeIter = constraintViolation.getPropertyPath().iterator();

Node node = nodeIter.next();
assert "author".equals( node.getName() );
assert ElementKind.PROPERTY.equals( node.getKind() );

node = nodeIter.next();
assert "lastName".equals( node.getName() );
assert ElementKind.PROPERTY.equals( node.getKind() );

assert false == nodeIter.hasNext();

5.2.2. Examples for method and constructor constraint violations

The following examples assume the constraint, class and object definitions given in the previous section. Additionally the following class and object definitions are assumed:

public class Library {

    @PublicLibrary
    public Library() {
        [...]
    }

    public Library(@NotNull @Valid List<Book> books) {
        [...]
    }

    public void addBook(@NotNull @Valid Book book) {
        [...]
    }

    @Valid public Map<Author, Book> getMostPopularBookPerAuthor() {
        [...]
    }
}

public class User {

    @OldAndNewPasswordsDifferent
    public void renewPassword(String oldPassword, String newPassword, String retypedNewPassword);
}

Library library = new Library();
author.setLastName("Doe");

Assuming the following invocation of addBook() is subject to method parameter validation:

library.addBook(null);

Then one ConstraintViolation object would be returned by ExecutableValidator.validateParameters() which satisfies the following assertions:

//assuming an english locale, the interpolated message is returned
assert "may not be null".equals( constraintViolation.getMessage() );

assert library == constraintViolation.getRootBean();
assert Library.class == constraintViolation.getRootBeanClass();
assert library == constraintViolation.getLeafBean();
assert null == constraintViolation.getInvalidValue();

assert new Object[]{ null }.equals( constraintViolation.getExecutableParameters() );
assert null == constraintViolation.getExecutableReturnValue();

Iterator<Node> nodeIter = constraintViolation.getPropertyPath().iterator();

Node node = nodeIter.next();
assert "addBook".equals( node.getName() );
assert ElementKind.METHOD.equals( node.getKind() );

node = nodeIter.next();
//assuming the default parameter name provider is used
assert "arg0".equals( node.getName() );
assert ElementKind.PARAMETER.equals( node.getKind() );

assert false == nodeIter.hasNext();

Assuming the following invocation of addBook() is subject to method parameter validation:

library.addBook(book);

Then one ConstraintViolation object would be returned by ExecutableValidator.validateParameters() which satisfies the following assertions:

//assuming an english locale, the interpolated message is returned
assert "may not be null or empty".equals( constraintViolation.getMessage() );

assert library == constraintViolation.getRootBean();
assert Library.class == constraintViolation.getRootBeanClass();
assert book == constraintViolation.getLeafBean();
assert book.getTitle().equals( constraintViolation.getInvalidValue() );

assert new Object[]{ book }.equals( constraintViolation.getExecutableParameters() );
assert null == constraintViolation.getExecutableReturnValue();

Iterator<Node> nodeIter = constraintViolation.getPropertyPath().iterator();

Node node = nodeIter.next();
assert "addBook".equals( node.getName() );
assert ElementKind.METHOD.equals( node.getKind() );

node = nodeIter.next();
//assuming the default parameter name provider is used
assert "arg0".equals( node.getName() );
assert ElementKind.PARAMETER.equals( node.getKind() );

node = nodeIter.next();
assert "title".equals( node.getName() );
assert ElementKind.PROPERTY.equals( node.getKind() );

assert false == nodeIter.hasNext();

Assuming the following invocation of User.renewPassword() is subject to method parameter validation and the @OldAndNewPasswordsDifferent constraint is violated:

User user = [...];
user.renewPassword("foo", "foo", "foo");

Then one ConstraintViolation object would be returned by ExecutableValidator.validateParameters() which satisfies the following assertions:

assert user == constraintViolation.getRootBean();
assert User.class == constraintViolation.getRootBeanClass();
assert user == getLeafBean();
assert new Object[]{ "foo", "foo", "foo" }.equals( constraintViolation.getInvalidValue() );

assert new Object[]{ "foo", "foo", "foo" }.equals( constraintViolation.getExecutableParameters() );
assert null == constraintViolation.getExecutableReturnValue();

Iterator<Node> nodeIter = constraintViolation.getPropertyPath().iterator();

Node node = nodeIter.next();
assert "renewPassword".equals( node.getName() );
assert ElementKind.METHOD.equals( node.getKind() );

node = nodeIter.next();
assert "<cross-parameter>" == node.getName();
assert ElementKind.CROSS_PARAMETER.equals( node.getKind() );

assert false == nodeIter.hasNext();

Assuming the following invocation of the Library constructor accepting a list of books is subject to constructor parameter validation:

Library anotherLibrary = new Library(null);

Then one ConstraintViolation object would be returned by ExecutableValidator.validateConstructorParameters() which satisfies the following assertions:

//assuming an english locale, the interpolated message is returned
assert "may not be null".equals( constraintViolation.getMessage() );

assert null == constraintViolation.getRootBean();
assert Library.class == constraintViolation.getRootBeanClass();
assert null == constraintViolation.getLeafBean();
assert null == constraintViolation.getInvalidValue();

assert new Object[]{ null }.equals( constraintViolation.getExecutableParameters() );
assert null == constraintViolation.getExecutableReturnValue();

Iterator<Node> nodeIter = constraintViolation.getPropertyPath().iterator();

Node node = nodeIter.next();
assert "Library".equals( node.getName() );
assert ElementKind.CONSTRUCTOR.equals( node.getKind() );

node = nodeIter.next();
//assuming the default parameter name provider is used
assert "arg0".equals( node.getName() );
assert ElementKind.PARAMETER.equals( node.getKind() );

assert false == nodeIter.hasNext();

Assuming the following invocation of getMostPopularBookPerAuthor() is subject to method return value validation and returns a Map containing one entry with key author and value book:

Map<Author, Book> mostPopularBookPerAuthor = library.getMostPopularBookPerAuthor();

Then one ConstraintViolation object would be returned by ExecutableValidator.validateReturnValue() which satisfies the following assertions:

//assuming an english locale, the interpolated message is returned
assert "may not be null or empty".equals( constraintViolation.getMessage() );

assert library == constraintViolation.getRootBean();
assert Library.class == constraintViolation.getRootBeanClass();
assert book == constraintViolation.getLeafBean();
assert book.getTitle().equals( constraintViolation.getInvalidValue() );

assert null == constraintViolation.getExecutableParameters();
assert mostPopularBookPerAuthor == constraintViolation.getExecutableReturnValue();

Iterator<Node> nodeIter = constraintViolation.getPropertyPath().iterator();

Node node = nodeIter.next();
assert "getMostPopularBookPerAuthor".equals( node.getName() );
assert ElementKind.METHOD.equals( node.getKind() );

node = nodeIter.next();
assert "<return value>" == node.getName();
assert ElementKind.RETURN_VALUE.equals( node.getKind() );

node = nodeIter.next();
assert "title".equals( node.getName() );
assert ElementKind.PROPERTY.equals( node.getKind() );
assert author.equals( node.getKey() );
assert true == node.isInIterable();

assert false == nodeIter.hasNext();

Assuming the following invocation of the Library default constructor is subject to constructor return value validation and returns an instance which violates the @PublicLibrary constraint:

Library publicLibrary = new Library();

Then one ConstraintViolation object would be returned by ExecutableValidator.validateConstructorReturnValue() which satisfies the following assertions:

assert null == constraintViolation.getRootBean();
assert Library.class == constraintViolation.getRootBeanClass();
assert publicLibrary == constraintViolation.getLeafBean();
assert publicLibrary == constraintViolation.getInvalidValue();

assert null == constraintViolation.getExecutableParameters();
assert library == constraintViolation.getExecutableReturnValue();

Iterator<Node> nodeIter = constraintViolation.getPropertyPath().iterator();

Node node = nodeIter.next();
assert "Library".equals( node.getName() );
assert ElementKind.CONSTRUCTOR.equals( node.getKind() );

node = nodeIter.next();
assert "<return value>" == node.getName();
assert ElementKind.RETURN_VALUE.equals( node.getKind() );

assert false == nodeIter.hasNext();

5.3. Message interpolation

A message interpolator is responsible for transforming the so called message descriptor specified via the message attribute of the constraint into a fully expanded, human-readable error message.

5.3.1. Default message interpolation

Every conforming Bean Validation implementation includes a default message interpolator which has to comply with the algorithm defined here to interpolate message descriptors. As precondition for message interpolation the following applies:

  • Each constraint defines a message descriptor via its message property.

  • Every constraint definition defines a default message descriptor for that constraint.

  • Messages can be overridden at constraint declaration time by setting the message property on the constraint.

The message descriptor is a string literal and may contain one or more message parameters or expressions. Message parameters and expressions are string literals enclosed in {} or ${} respectively. The following character escaping rules apply:

  • \{ is considered as the literal { instead of being considered as the beginning of a message parameter

  • \} is considered as the literal } instead of being considered as the end of a message parameter

  • \\ is considered as the literal \ instead of being considered as the escaping character

  • \$ is considered as the literal $ instead of being considered as the beginning of a message expression

Below are two examples using message parameters and expressions. The second is evaluated using Expression Language as defined in Section 5.3.1.3, “Message expressions using Expression Language (EL)”.

Example 5.8. Message using parameters

Value must be between {min} and {max}

Example 5.9. Message using expressions

Must be greater than ${inclusive == true ? 'or equal to ' : ''}{value}

5.3.1.1. Default message interpolation algorithm

The default message interpolator uses the following steps:

  1. Message parameters are extracted from the message string and used as keys to search the ResourceBundle named ValidationMessages (often materialized as the property file /ValidationMessages.properties and its locale variations) using the defined locale (see Section 5.3.1.2, “Locale for default message interpolation”). If a property is found, the message parameter is replaced with the property value in the message string. Step 1 is applied recursively until no replacement is performed (i.e. a message parameter value can itself contain a message parameter).

  2. Message parameters are extracted from the message string and used as keys to search the Bean Validation provider's built-in ResourceBundle using the defined locale (see Section 5.3.1.2, “Locale for default message interpolation”). If a property is found, the message parameter is replaced with the property value in the message string. Contrary to step 1, step 2 is not processed recursively.

  3. If step 2 triggers a replacement, then step 1 is applied again. Otherwise step 4 is performed.

  4. Message parameters are extracted from the message string. Those matching the name of an attribute of the constraint are replaced by the value of that attribute in the constraint declaration. Parameter interpolation has precedence over message expressions. For example for the message descriptor ${value}, trying to evaluate {value} as message parameter has precedence over evaluating ${value} as message expression.

  5. Message expressions are extracted from the message string and evaluated using Expression Language. See also Section 5.3.1.3, “Message expressions using Expression Language (EL)”.

Note

The proposed algorithm ensures that custom resource bundle always have priority over built-in resource bundle at all level of the recursive resolution. It also ensures that constraint declarations attributes values are not interpolated further.

Note

The precedence of message parameter over expression interpolation ensures backwards compatibility to Bean Validation 1.0.

5.3.1.2. Locale for default message interpolation

The locale to be used for message interpolation is defined as following:

  • if the locale is passed explicitly to the interpolator method via interpolate(String, Context, Locale), this provided instance is used.

  • otherwise, the default Locale as provided by Locale.getDefault() is used.

5.3.1.3. Message expressions using Expression Language (EL)

The default message interpolation allows the use of Expression Language (EL) as defined in JSR 341. Expressions to be evaluated by EL need to be enclosed in ${} within the message descriptor. The following properties and beans have to be made available in the EL context:

  • the attribute values of the constraint declaration mapped to their attribute name

  • the validated value mapped under the name validatedValue.

  • a bean mapped to the name formatter exposing the vararg method format(String format, Object... args). This method must behave like java.util.Formatter.format(String format, Object... args). The locale used for formatting is defined by Section 5.3.1.2, “Locale for default message interpolation”. The formatter bean allows to format property values, for example in the case of the validated value being 98.12345678, ${formatter.format('%1$.2f', validatedValue)} would format it to 98.12 (two digits after the decimal point, where the use of '.' vs ',' would be locale specific).

If an exception occurs during message interpolation, e.g. due invalid expressions or references to an unknown property, the message expression stays unchanged.

5.3.2. Custom message interpolation

A custom message interpolator may be provided (e.g., to interpolate contextual data, or to adjust the default Locale used). A message interpolator implements the MessageInterpolator interface.

/**
 * Interpolates a given constraint violation message.
 * <p/>
 * Implementations should be as tolerant as possible on syntax errors.
 * Implementations must be thread-safe.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 */
public interface MessageInterpolator {

    /**
     * Interpolates the message template based on the constraint validation context.
     * <p/>
     * The locale is defaulted according to the {@code MessageInterpolator}
     * implementation. See the implementation documentation for more detail.
     *
     * @param messageTemplate the message to interpolate
     * @param context contextual information related to the interpolation
     *
     * @return interpolated error message
     */
    String interpolate(String messageTemplate, Context context);

    /**
     * Interpolates the message template based on the constraint validation context.
     * The {@code Locale} used is provided as a parameter.
     *
     * @param messageTemplate the message to interpolate
     * @param context contextual information related to the interpolation
     * @param locale the locale targeted for the message
     *
     * @return interpolated error message
     */
    String interpolate(String messageTemplate, Context context,  Locale locale);

    /**
     * Information related to the interpolation context.
     */
    interface Context {
        /**
         * @return {@link ConstraintDescriptor} corresponding to the constraint being validated
         */
        ConstraintDescriptor<?> getConstraintDescriptor();

        /**
         * @return value being validated
         */
        Object getValidatedValue();

        /**
         * Returns an instance of the specified type allowing access to
         * provider-specific APIs. If the Bean Validation provider
         * implementation does not support the specified class,
         * {@link ValidationException} is thrown.
         *
         * @param type the class of the object to be returned
         * @return an instance of the specified class
         * @throws ValidationException if the provider does not support the call
         *
         * @since 1.1
         */
        <T> T unwrap(Class<T> type);
    }
}

messageTemplate is the value of the message attribute of the constraint declaration or provided to the ConstraintValidatorContext methods.

The Context object contains contextual information related to the interpolation.

getConstraintDescriptor() returns the ConstraintDescriptor object representing the metadata of the failing constraint (see Chapter 6, Constraint metadata request APIs).

getValidatedValue() returns the value being validated.

MessageInterpolator.interpolate(String, Context) is invoked for each constraint violation report generated. The default Locale is implementation specific.

MessageInterpolator.interpolate(String, Context, Locale) can be invoked by a wrapping MessageInterpolator to enforce a specific Locale value by bypassing or overriding the default Locale strategy (see Example 5.10, “Use MessageInterpolator to use a specific Locale value”).

A message interpolator implementation must be thread-safe.

The message interpolator is provided to the ValidatorFactory at construction time using Configuration.messageInterpolator(MessageInterpolator). This message interpolator is shared by all Validator objects generated by this ValidatorFactory.

It is possible to override the MessageInterpolator implementation for a given Validator instance by invoking ValidatorFactory.usingContext().messageInterpolator(messageInterpolator).getValidator().

It is recommended that MessageInterpolator implementations delegate final interpolation to the Bean Validation default MessageInterpolator to ensure standard Bean Validation interpolation rules are followed, The default implementation is accessible through Configuration.getDefaultMessageInterpolator().

If the interpolation process leads to an exception, the exception is wrapped into a ValidationException.

5.3.3. Examples

These examples describe message interpolation based on the default message interpolator's built-in messages (see Appendix B, Standard ResourceBundle messages), and the ValidationMessages.properties file shown in table Table 5.3, “message interpolation”. The current locale is assumed English.

//ValidationMessages.properties
myapp.creditcard.error=credit card number not valid

Table 5.3. message interpolation

Failing constraint declarationinterpolated message
@NotNullmust not be null
@Max(30)must be less than or equal to 30
@Size(min=5, max=15, message="Key must have \\{{min}\\} \\ \\{{max}\\} characters")Key must have {5} \ {15} characters
@Digits(integer=9, fraction=2)numeric value out of bounds (<9 digits>.<2 digits> expected)
@CreditCard(message={myapp.creditcard.error})credit card number not valid

Here is an approach to specify the Locale value to choose on a given Validator. Locale aware MessageInterpolator. See Section 5.5, “Bootstrapping” for more details on the APIs.

Example 5.10. Use MessageInterpolator to use a specific Locale value

/**
 * Delegates to a MessageInterpolator implementation but enforces a given Locale
 */
public class LocaleSpecificMessageInterpolator implements MessageInterpolator {
    private final MessageInterpolator defaultInterpolator;
    private final Locale defaultLocale;

    public LocaleSpecificMessageInterpolator(MessageInterpolator interpolator, Locale locale) {
        this.defaultLocale = locale;
        this.defaultInterpolator = interpolator;
    }

    /**
     * enforces the locale passed to the interpolator
     */
    public String interpolate(String message, 
                              Context context) {
        return defaultInterpolator.interpolate(message, 
                                               context, 
                                               this.defaultLocale);
    }

    // no real use, implemented for completeness
    public String interpolate(String message,
                              Context context,
                              Locale locale) {
        return defaultInterpolator.interpolate(message, context, locale);
    }
}


Locale locale = getMyCurrentLocale();
MessageInterpolator interpolator = new LocaleSpecificMessageInterpolator(
                                       validatorFactory.getMessageInterpolator(),
                                       locale);

Validator validator = validatorFactory.usingContext()
                                      .messageInterpolator(interpolator)
                                      .getValidator();

Most of the time, however, the relevant Locale will be provided by your application framework transparently. This framework will implement its own version of MessageInterpolator and pass it during the ValidatorFactory configuration. The application will not have to set the Locale itself. This example shows how a container framework would implement MessageInterpolator to provide a user specific default locale.

Example 5.11. Contextual container possible MessageInterpolator implementation

public class ContextualMessageInterpolator implements MessageInterpolator {
    private final MessageInterpolator delegate;

    public ContextualMessageInterpolator(MessageInterpolator delegate) { 
        this.delegate = delegate; 
    }

    public String interpolate(String message, Context context) {
        Locale locale = Container.getManager().getUserLocale();
        return this.delegate.interpolate(
                        message, context, locale );
    }

    public String interpolate(String message, Context context, Locale locale) {
        return this.delegate.interpolate(message, context, locale);
    }
}


//Build the ValidatorFactory
Configuration<?> configuration = Validation.byDefaultProvider().configure();
ValidatorFactory factory = configuration
    .messageInterpolator( 
        new ContextualMessageInterpolator( 
                configuration.getDefaultMessageInterpolator() ) )
    .buildValidatorFactory();

//The container uses the factory to validate constraints using the specific MessageInterpolator
Validator validator = factory.getValidator();

5.4. Triggering method validation

Bean Validation itself doesn't trigger the evaluation of method constraints. That is, just annotating any methods or constructors with parameter or return value constraints doesn't automatically enforce these constraints, just as annotating any fields or properties with bean constraints doesn't enforce these either.

Instead method constraints must be validated by invoking the appropriate methods on javax.validation.executable.ExecutableValidator. Typically this won't happen by manually calling these methods but rather automatically upon invocation of the constrained methods or constructors, using approaches and techniques such as CDI/EJB interceptors, aspect-oriented programming or dynamic proxies.

The validation of method / constructor constraints comprises the following steps:

  • Intercept the method call to be validated

  • Validate the parameter values provided by the method caller using ExecutableValidator.validateParameters() or ExecutableValidator.validateConstructorParameters().

  • If this validation yields a non-empty set of constraint violations, throw a ConstraintViolationException wrapping the violations. Otherwise proceed with the actual method invocation.

  • Validate the result returned by the invoked method using ExecutableValidator.validateReturnValue() or ExecutableValidator.validateConstructorReturnValue().

  • If this validation yields a non-empty set of constraint violations, throw a ConstraintViolationException wrapping the violations. Otherwise return the invocation result to the method caller.

By throwing a ConstraintViolationException if either of the validation steps fails, it is ensured that the control flow

  • only arrives at the method's body if the caller has satisfied the method's preconditions and

  • only returns to the method caller if the method's postconditions are guaranteed.

By default, integrators intercept and validate methods hosting either a constraint or being marked for cascaded validation (@Valid) whether it be on the method itself or on any of its parameters. The Default group is used for validation out of the box.

Integrators are encouraged to use Bean Validation's metadata API to find whether or not a method or a constructor should be intercepted. This guarantees that XML descriptors as well as future mapping strategies are taken into account. Note that the metadata API does not take into account the fact that a method or constructor validation has been enabled or disabled by the techniques described in Section 10.1.2, “Method and constructor validation”.

Here is an example of what such metadata usage would be:

Example 5.12. Using metadata API to figure out if method interception is required

//For methods

// is there any constrained method on this type
// assuming we don't validate on getter execution
public boolean interceptMethods(Class<?> type) {
    return validator.getConstraintsForClass( type ).getConstrainedMethods(MethodType.NON_GETTER).size() > 0;
}

// is this method constrained
public boolean interceptMethod(Class<?> type, Method method) {
    BeanDescriptor bean = validator.getConstraintsForClass( type );
    MethodDescriptor methodDescriptor = bean.getConstraintsForMethod(
        method.getName(), method.getParameterTypes() );
    return methodDescriptor != null;
}

// should method parameters be validated
public boolean requiresParametersValidation(Class<?> type, Method method) {
    BeanDescriptor bean = validator.getConstraintsForClass( type );
    MethodDescriptor methodDescriptor = bean.getConstraintsForMethod(
        method.getName(), method.getParameterTypes() );
    if ( methodDescriptor != null ) {
        return methodDescriptor.hasConstrainedParameters();
    }
    else {
        return false;
    }
}

// should method return value be validated?
public boolean requiresReturnValueValidation(Class<?> type, Method method) {
    BeanDescriptor bean = validator.getConstraintsForClass( type );
    MethodDescriptor methodDescriptor = bean.getConstraintsForMethod(
        method.getName(), method.getParameterTypes() );
    if ( methodDescriptor != null ) {
        return methodDescriptor.hasConstrainedReturnValue();
    }
    else {
        return false;
    }
}

Example 5.13. Using metadata API to figure out if constructor interception is required

//For constructors

// is there any constrained constructor on this type
public <T> boolean interceptConstructors(Class<T> type) {
    BeanDescriptor bean = validator.getConstraintsForClass( type );
    return bean.getConstrainedConstructors().size() > 0;
}

// is this constructor constrained
public <T> boolean interceptConstructor(Class<T> type, Constructor<T> ctor) {
    BeanDescriptor bean = validator.getConstraintsForClass( type );
    ConstructorDescriptor constructorDescriptor = bean.getConstraintsForConstructor(
        ctor.getParameterTypes() );
    return constructorDescriptor != null;
}

// should constructor parameters be validated
public <T> boolean requiresParametersValidation(Class<T> type, Constructor<T> ctor) {
    BeanDescriptor bean = validator.getConstraintsForClass( type );
    ConstructorDescriptor constructorDescriptor = bean.getConstraintsForConstructor(
        ctor.getParameterTypes() );
    if ( constructorDescriptor != null ) {
        return constructorDescriptor.hasConstrainedParameters();
    }
    else {
        return false;
    }
}

// should constructor return value be validated?
public <T> boolean requiresReturnValueValidation(Class<T> type, Constructor<T> ctor) {
    BeanDescriptor bean = validator.getConstraintsForClass( type );
    ConstructorDescriptor constructorDescriptor = bean.getConstraintsForConstructor(
        ctor.getName(), 
        ctor.getParameterTypes()
    );
    if ( constructorDescriptor != null ) {
        return constructorDescriptor.hasConstrainedReturnValue();
    }
    else {
        return false;
    }
}

Note

Calls to the metadata API is likely only going to be needed during the initialization phase of the interception framework. Results can then be cached.

Note

Only methods or constructors intercepted by the underlying interception technology can be validated.

The integration technology must put the validation interceptor as late as possible (if not last) in the interception stack. In particular, validation of parameters should be done after the security and transaction start logic. Likewise, return value validation should be done before the transaction stop logic. Putting the validation interceptor as late as possible in the stack ensures this.

Why have the validation interceptor after other interceptors?

There are several reasons for delaying validation compared to other interceptors:

  • You don't want to start business code before security has been cleared

  • You might need transaction support in your validations

  • You want transaction to fail if the return value is invalid

  • Generally speaking, it makes more sense to apply technical layers around the more business focused constraints

5.5. Bootstrapping

The bootstrapping API aims at providing a ValidatorFactory object which is used to create Validator instances. The bootstrap process is decoupled from the provider implementation initialization: a bootstrap implementation must be able to bootstrap any Bean Validation provider implementation. The bootstrap sequence has been designed to achieve several goals:

  • plug multiple implementations

  • choose a specific implementation

  • extensibility: an application using a specific provider implementation can use specific configurations

  • share and reuse of metadata across Validators

  • leave as much freedom as possible to implementations

  • provide integration mechanisms to Java EE (starting from version 6) and other containers

  • type safety

The main artifacts involved in the bootstrap process are:

  • Validation: API entry point. Lets you optionally define the Bean Validation provider targeted as well as a provider resolution strategy. Validation generates Configuration objects and can bootstrap any provider implementation.

  • ValidationProvider: contract between the bootstrap procedure and a Bean Validation provider implementation.

  • ValidationProviderResolver: returns a list of all Bean Validation providers available in the execution context (generally the classpath).

  • Configuration: collects the configuration details that will be used to build ValidatorFactory. A specific sub interface of Configuration must be provided by Bean Validation providers. This sub interface typically hosts provider specific configurations.

  • ValidatorFactory: result of the bootstrap process. Build Validator instances from a given Bean Validation provider.

  • META-INF/validation.xml: a configuration file Bean Validation users can use to customize the configuration of the default ValidatorFactory.

Let's first see the API in action through some examples before diving into the concrete definitions.

5.5.1. Examples

The most simple approach is to initialize the default Bean Validation provider or the one defined in the XML configuration file. The ValidatorFactory is then ready to provide Validator instances.

Example 5.14. Simple Bean Validation bootstrap sequence

ValidatorFactory factory = Validation.buildDefaultValidatorFactory();

//cache the factory somewhere
Validator validator = factory.getValidator();

//when the application shuts down, close ValidatorFactory
factory.close();

The ValidatorFactory object is thread-safe. Building Validator instances is typically a cheap operation. Building a ValidatorFactory is typically more expensive. Make sure to check your Bean Validation implementation documentation for more accurate details.

The second example shows how a container can customize some Bean Validator resource handling to match its own behavior.

Example 5.15. Customize message resolution, traversable resolver, constraint Validator factory and parameter name provider implementation

//some customization from a container
ValidatorFactory factory = Validation
       .byDefaultProvider().configure()
          .messageInterpolator( new ContainerMessageInterpolator() )
          .constraintValidatorFactory( new ContainerComponentConstraintValidatorFactory() )
          .traversableResolver( new JPAAwareTraversableResolver() )
          .parameterNameProvider( new AnnotationBasedParameterNameProvider() )
          .buildValidatorFactory();

//cache the factory somewhere
Validator validator = factory.getValidator();

//when the application shuts down, close ValidatorFactory
factory.close();

The third example shows how to bootstrap Bean Validation in an environment not following the traditional Java classloader strategies (such as tools or alternative service containers like OSGi). They can provider some alternative provider resolution strategy to discover Bean Validation providers.

Example 5.16. Customize the Bean Validation provider resolution mechanism

//osgi environment
ValidatorFactory factory = Validation
       .byDefaultProvider()
          .providerResolver( new OSGiServiceDiscoverer() )
          .configure()
             .buildValidatorFactory();

//cache the factory somewhere
Validator validator = factory.getValidator();

//when the bundle shuts down, close ValidatorFactory
factory.close();

The next example shows how a client can choose a specific Bean Validation provider and configure provider specific properties programmatically in a type-safe way.

Example 5.17. Use a specific provider and add specific configuration

ValidatorFactory factory = Validation
       .byProvider( ACMEProvider.class )  //chose a specific provider
       .configure()
          .messageInterpolator( new ContainerMessageInterpolator() ) //default configuration option
          .addConstraint(Address.class, customConstraintDescriptor) //ACME specific method
          .buildValidatorFactory();

//same initialization decomposing calls
ACMEConfiguration acmeConfiguration = Validation
       .byProvider( ACMEProvider.class )
       .configure();

ValidatorFactory factory = acmeConfiguration
          .messageInterpolator( new ContainerMessageInterpolator() ) //default configuration option
          .addConstraint(Address.class, customConstraintDescriptor) //ACME specific method
          .buildValidatorFactory();

/**
 * ACME specific validator configuration and configuration options
 */
public interface ACMEConfiguration extends Configuration<ACMEConfiguration> {
    /**
     * Programmatically add constraints. Specific to the ACME provider.
     */
    ACMEConfiguration addConstraint(Class<?> entity, 
                                    ACMEConstraintDescriptor constraintDescriptor);
}

/**
 * ACME validation provider
 * Note how ACMEConfiguration and ACMEProvider are linked together 
 * via the generic parameter.
 */
public class ACMEProvider implements ValidationProvider<ACMEConfiguration> {
    [...]
}

The last example shows how a Validator can use a specific MessageInterpolator implementation

Example 5.18. Use a specific MessageInterpolator instance for a given Validator

ValidatorFactory factory = [...];
MessageInterpolator customInterpolator = new LocaleSpecificMessageInterpolator(
    locale, 
    factory.getMessageInterpolator()
);

Validator localizedValidator = 
    factory.usingContext()
                   .messageInterpolator(customInterpolator)
                   .getValidator();

In the same way, a custom TraversableResolver can be passed.

We will now explore the various interfaces, their constraints and usage. We will go from the ValidatorFactory to the Validation class walking up the bootstrap chain.

5.5.2. ValidatorFactory

ValidatorFactory objects build and provide initialized instances of Validator to Bean Validation clients. Each Validator instance is configured for a given context (message interpolator, traversable resolver etc.). Clients should cache ValidatorFactory objects and reuse them for optimal performances. The API is designed to allow implementors to share constraint metadata in ValidatorFactory. ValidatorFactory instances must be closed (by calling the close() method) by its creator when no longer in use.

ValidatorFactory implementations must be thread-safe. ValidatorFactory implementations can cache Validator instances if needed.

Example 5.19. ValidatorFactory interface

/**
 * Factory returning initialized {@code Validator} instances.
 * <p/>
 * Implementations are thread-safe and instances are typically cached and reused.
 *
 * @author Emmanuel Bernard
 * @author Gunnar Morling
 * @author Hardy Ferentschik
 */
public interface ValidatorFactory {

    /**
     * Returns an initialized {@link Validator} instance using the
     * factory defaults for message interpolator, traversable resolver
     * and constraint validator factory.
     * <p/>
     * Validator instances can be pooled and shared by the implementation.
     *
     * @return an initialized {@code Validator} instance
     */
    Validator getValidator();

    /**
     * Defines a new validator context and returns a {@code Validator}
     * compliant this new context.
     *
     * @return a {@link ValidatorContext} instance
     */
    ValidatorContext usingContext();

    /**
     * Returns the {@link MessageInterpolator} instance configured at
     * initialization time for the {@code ValidatorFactory}.
     * This is the instance used by {@link #getValidator()}.
     *
     * @return {@code MessageInterpolator} instance
     */
    MessageInterpolator getMessageInterpolator();

    /**
     * Returns the {@link TraversableResolver} instance configured
     * at initialization time for the {@code ValidatorFactory}.
     * This is the instance used by {@link #getValidator()}.
     *
     * @return {@code TraversableResolver} instance
     */
    TraversableResolver getTraversableResolver();

    /**
     * Returns the {@link ConstraintValidatorFactory} instance
     * configured at initialization time for the
     * {@code ValidatorFactory}.
     * This is the instance used by {@link #getValidator()}.
     *
     * @return {@code ConstraintValidatorFactory} instance
     */
    ConstraintValidatorFactory getConstraintValidatorFactory();

    /**
     * Returns the {@link ParameterNameProvider} instance configured at
     * initialization time for the {@code ValidatorFactory}.
     * This is the instance used by #getValidator().
     *
     * @return {@code ParameterNameProvider} instance
     *
     * @since 1.1
     */
    ParameterNameProvider getParameterNameProvider();

    /**
     * Returns an instance of the specified type allowing access to
     * provider-specific APIs. If the Bean Validation provider
     * implementation does not support the specified class, a
     * {@code ValidationException} is thrown.
     *
     * @param type the class of the object to be returned
     * @return an instance of the specified class
     * @throws ValidationException if the provider does not
     *         support the call.
     */
    public <T> T unwrap(Class<T> type);

    /**
     * Closes the {@code ValidatorFactory} instance.
     *
     * After the {@code ValidatorFactory} instance is closed, calling the following
     * methods is not allowed:
     * <ul>
     *     <li>methods of this {@code ValidatorFactory} instance</li>
     *     <li>methods of {@link Validator} instances created by this {@code ValidatorFactory}</li>
     * </ul>
     *
     * @since 1.1
     */
    public void close();
}

A ValidatorFactory is provided by a Configuration object.

unwrap() is provided as a way to access objects of a given type specific to a Bean Validation provider typically as a complement to the ValidatorFactory contract. Using this method makes your code non portable.

Example 5.20. Using unwrap to access a provider specific contract

//if using the ACME provider
ACMEValidatorFactory acmeFactory = factory.unwrap(ACMEValidatorFactory.class);
acmeFactory.setSpecificConfiguration( [...] );

close() closes the ValidatorFactory instance which becomes unavailable and should be immediately discarded. This is also true of all the Validator instances it has spawned. The behavior is undefined and non portable if these instances are used after the ValidatorFactory has been closed.

getMessageInterpolator() returns the MessageInterpolator instance configured during the initialization of the ValidatorFactory. It is particularly useful to build a Validator specific MessageInterpolator wrapping the one from the ValidatorFactory.

getTraversableResolver() returns the TraversableResolver instance configured during the initialization of the ValidatorFactory. It is particularly useful to build a Validator specific TraversableResolver wrapping the one from the ValidatorFactory.

getConstraintValidatorFactory() returns the ConstraintValidatorFactory instance configured during the initialization of the ValidatorFactory. It is particularly useful to build a Validator specific ConstraintValidatorFactory wrapping the one from the ValidatorFactory.

getParameterNameProvider() returns the ParameterNameProvider instance configured during the initialization of the ValidatorFactory. It is particularly useful to build a Validator specific ParameterNameProvider wrapping the one from the ValidatorFactory.

ValidatorContext returned by usingContext() can be used to customize the state in which the Validator must be initialized. This is used to customize the MessageInterpolator, the TraversableResolver, ParameterNameProvider or the ConstraintValidatorFactory.

Example 5.21. ValidatorContext interface

/**
 * Represents the context that is used to create {@link Validator}
 * instances.
 *
 * A client may use methods of the {@code ValidatorContext} returned by
 * {@link ValidatorFactory#usingContext()} to customize
 * the context used to create {@code Validator} instances
 * (for instance establish different message interpolators or
 * traversable resolvers).
 *
 * @author Emmanuel Bernard
 * @author Gunnar Morling
 */
public interface ValidatorContext {

    /**
     * Defines the message interpolator implementation used by the
     * {@link Validator}.
     * <p/>
     * If not set or if {@code null} is passed as a parameter,
     * the message interpolator of the {@link ValidatorFactory}
     * is used.
     *
     * @param messageInterpolator the {@link MessageInterpolator} used by the {@code Validator}
     *
     * @return self following the chaining method pattern
     */
    ValidatorContext messageInterpolator(MessageInterpolator messageInterpolator);

    /**
     * Defines the traversable resolver implementation used by the
     * {@link Validator}.
     * <p/>
     * If not set or if {@code null} is passed as a parameter,
     * the traversable resolver of the {@link ValidatorFactory} is used.
     *
     * @param traversableResolver the {@code TraversableResolver} used by the {@code Validator}
     * @return self following the chaining method pattern
     */
    ValidatorContext traversableResolver(TraversableResolver traversableResolver);

    /**
     * Defines the constraint validator factory implementation used by the
     * {@link Validator}.
     * If not set or if {@code null} is passed as a parameter,
     * the constraint validator factory of the {@link ValidatorFactory} is used.
     *
     * @param factory the {@link ConstraintValidatorFactory} used by the {@code Validator}
     * @return self following the chaining method pattern
     */
    ValidatorContext constraintValidatorFactory(ConstraintValidatorFactory factory);

    /**
     * Defines the parameter name provider implementation used by the
     * {@link Validator}. If not set or if {@code null} is passed as a parameter,
     * the parameter name provider of the {@link ValidatorFactory} is used.
     *
     * @param parameterNameProvider parameter name provider implementation.
     * @return self following the chaining method pattern
     *
     * @since 1.1
     */
    ValidatorContext parameterNameProvider(ParameterNameProvider parameterNameProvider);

    /**
     * Returns an initialized {@link Validator} instance respecting the defined state.
     * {@code Validator} instances can be pooled and shared by the implementation.
     *
     * @return contextualized {@code Validator}
     */
    Validator getValidator();
}

The MessageInterpolator, the TraversableResolver, the ConstraintValidatorFactory or the ParameterNameProvider passed to the ValidatorContext are used instead of the ValidatorFactory's MessageInterpolator, TraversableResolver, ConstraintValidatorFactory or ParameterNameProvider instances.

Example 5.22. Use of ValidatorFactory

ValidatorFactory factory = [...];
Validator validatorUsingDefaults = factory.getValidator();
Validator validatorUsingCustomTraversable = factory
                     .usingContext()
                     .traversableResolver( new JPATraversableResolver() )
                     .getValidator();

See Example 5.10, “Use MessageInterpolator to use a specific Locale value” for an example using ValidatorFactory.getMessageInterpolator().

5.5.3. Configuration

The responsibility of the Configuration is to collect configuration information, to determine the correct provider implementation and to delegate the ValidatorFactory creation to the seleced provider. More concretely Configuration lets you define:

  • the message interpolator instance

  • the traversable resolver instance

  • the constraint validator factory instance

  • the parameter name provider instance

  • XML constraint mappings

  • provider specific properties

  • whether or not META-INF/validation.xml is considered

Configuration does provide a MessageInterpolator implementation following the default Bean Validation MessageInterpolator rules as defined in Section 5.3.1, “Default message interpolation”. You can access it by calling getDefaultMessageInterpolator(). Such an implementation is useful to let a custom MessageInterpolator delegate to the standard MessageInterpolator (see Section 5.3.2, “Custom message interpolation” and an example making use of getDefaultMessageInterpolator() in Example 5.11, “Contextual container possible MessageInterpolator implementation”).

Configuration does provide a TraversableResolver implementation following the default Bean Validation TraversableResolver rules as defined in Section 4.6.3, “Traversable property”. You can access it by calling getDefaultTraversableResolver(). Such an implementation is useful to let a custom TraversableResolver delegate to the standard TraversableResolver.

Configuration does provide a ConstraintValidatorFactory implementation following the default Bean Validation ConstraintValidatorFactory rules as defined in Section 3.5, “The ConstraintValidatorFactory”. You can access it by calling getDefaultConstraintValidatorFactory(). Such an implementation is useful to let a custom ConstraintValidatorFactory delegate to the standard ConstraintValidatorFactory.

Configuration does provide a ParameterNameProvider implementation following the default Bean Validation ParameterNameProvider rules as defined in Section 4.5.2.2, “Naming parameters”. You can access it by calling getDefaultParameterNameProvider(). Such an implementation is useful to let a custom ParameterNameProvider delegate to the standard ParameterNameProvider.

Via getBootstrapConfiguration(), Configuration also exposes data stored in META-INF/validation.xml (see Section 5.5.6, “XML configuration: META-INF/validation.xml”). This is particularly useful for containers wishing to control the instance creation and life cycle (more information at Section 5.5.7, “Bootstrapping considerations”).

Note

BootstrapConfiguration.getDefaultValidatedExecutableTypes() and BootstrapConfiguration.isExecutableValidationEnabled() are not used by the Bean Validation engine but exposed here for interception technologies - see Section 10.1.2, “Method and constructor validation”.

Using addMapping(), additional constraint mapping XML descriptors can be added to the configuration (see Section 5.5.6, “XML configuration: META-INF/validation.xml”). The given input streams should support the mark() and reset() methods defined by java.io.InputStream. Streams not supporting the mark() and reset() methods will be wrapped with an InputStream implementation supporting these methods by the Bean Validation provider in order to allow the streams to be read several times.

Clients call Configuration.buildValidatorFactory() to retrieve the initialized ValidatorFactory instance. It is legal to invoke buildValidatorFactory() several times, e.g. in order to retrieval several ValidatorFactory instances with a slightly different configuration (see Example 5.27, “Using Configuration to create several validator factories”).

Example 5.23. Configuration and BootstrapConfiguration interfaces

/**
 * Receives configuration information, selects the appropriate
 * Bean Validation provider and builds the appropriate {@link ValidatorFactory}.
 * <p/>
 * Usage:
 * <pre>
 * Configuration<?> configuration = //provided by one of the Validation bootstrap methods
 *     ValidatorFactory = configuration
 *         .messageInterpolator( new CustomMessageInterpolator() )
 *         .buildValidatorFactory();
 * </pre>
 * <p/>
 * By default, the configuration information is retrieved from
 * {@code META-INF/validation.xml}.
 * It is possible to override the configuration retrieved from the XML file
 * by using one or more of the {@code Configuration} methods.
 * <p/>
 * The {@link ValidationProviderResolver} is specified at configuration time
 * (see {@link ValidationProvider}).
 * If none is explicitly requested, the default {@code ValidationProviderResolver} is used.
 * <p/>
 * The provider is selected in the following way:
 * <ul>
 *     <li>if a specific provider is requested programmatically using
 *     {@link Validation#byProvider(Class)}, find the first provider implementing
 *     the provider class requested and use it</li>
 *     <li>if a specific provider is requested in {@code META-INF/validation.xml}>,
 *     find the first provider implementing the provider class requested and use it</li>
 *     <li>otherwise, use the first provider returned by the {@code ValidationProviderResolver}</li>
 * </ul>
 * <p/>
 * Implementations are not meant to be thread-safe.
 *
 * @author Emmanuel Bernard
 * @author Gunnar Morling
 * @author Hardy Ferentschik
 */
public interface Configuration<T extends Configuration<T>> {

    /**
     * Ignores data from the {@code META-INF/validation.xml} file if this
     * method is called.
     * <p/>
     * This method is typically useful for containers that parse
     * {@code META-INF/validation.xml} themselves and pass the information
     * via the {@code Configuration} methods.
     *
     * @return {@code this} following the chaining method pattern.
     */
    T ignoreXmlConfiguration();

    /**
     * Defines the message interpolator used. Has priority over the configuration
     * based message interpolator.
     * <p/>
     * If {@code null} is passed, the default message interpolator is used
     * (defined in XML or the specification default).
     *
     * @param interpolator message interpolator implementation
     * @return {@code this} following the chaining method pattern
     */
    T messageInterpolator(MessageInterpolator interpolator);

    /**
     * Defines the traversable resolver used. Has priority over the configuration
     * based traversable resolver.
     * <p/>
     * If {@code null} is passed, the default traversable resolver is used
     * (defined in XML or the specification default).
     *
     * @param resolver traversable resolver implementation
     * @return {@code this} following the chaining method pattern
     */
    T traversableResolver(TraversableResolver resolver);

    /**
     * Defines the constraint validator factory. Has priority over the configuration
     * based constraint factory.
     * <p/>
     * If {@code null} is passed, the default constraint validator factory is used
     * (defined in XML or the specification default).
     *
     * @param constraintValidatorFactory constraint factory implementation
     * @return {@code this} following the chaining method pattern
     */
    T constraintValidatorFactory(ConstraintValidatorFactory constraintValidatorFactory);

    /**
     * Defines the parameter name provider. Has priority over the configuration
     * based provider.
     * <p/>
     * If {@code null} is passed, the default parameter name provider is used
     * (defined in XML or the specification default).
     *
     * @param parameterNameProvider parameter name provider implementation
     * @return {@code this} following the chaining method pattern.
     *
     * @since 1.1
     */
    T parameterNameProvider(ParameterNameProvider parameterNameProvider);

    /**
     * Add a stream describing constraint mapping in the Bean Validation XML
     * format.
     * <p/>
     * The stream should be closed by the client API after the
     * {@link ValidatorFactory} has been built. The Bean Validation provider
     * must not close the stream.
     *
     * @param stream
     *        XML mapping stream; the given stream should support the
     *        mark/reset contract (see {@link InputStream#markSupported()});
     *        if it doesn't, it will be wrapped into a stream supporting the
     *        mark/reset contract by the Bean Validation provider
     *
     * @return {@code this} following the chaining method pattern
     * @throws IllegalArgumentException if {@code stream} is null
     */
    T addMapping(InputStream stream);

    /**
     * Adds a provider specific property. This property is equivalent to
     * XML configuration properties.
     * If the underlying provider does not know how to handle the property,
     * it must silently ignore it.
     * <p/>
     * Note: Using this non type-safe method is generally not recommended.
     * <p/>
     * It is more appropriate to use, if available, the type-safe equivalent provided
     * by a specific provider via its {@link Configuration} subclass.
     * <pre>
     * ValidatorFactory factory = Validation.byProvider(ACMEProvider.class)
     *     .configure()
     *         .providerSpecificProperty(ACMEState.FAST)
     *     .buildValidatorFactory();
     * </pre>
     * This method is typically used by containers parsing {@code META-INF/validation.xml}
     * themselves and injecting the state to the {@code Configuration} object.
     * <p/>
     * If a property with a given name is defined both via this method and in the
     * XML configuration, the value set programmatically has priority.
     * <p/>
     * If {@code null} is passed as a value, the value defined in XML is used. If no value
     * is defined in XML, the property is considered unset.
     *
     * @param name property name
     * @param value property value
     * @return {@code this} following the chaining method pattern
     * @throws IllegalArgumentException if {@code name} is null
     */
    T addProperty(String name, String value);

    /**
     * Returns an implementation of the {@link MessageInterpolator} interface
     * following the default {@code MessageInterpolator} defined in the
     * specification:
     * <ul>
     *     <li>use the {@code ValidationMessages} resource bundle to load keys</li>
     *     <li>use {@code Locale.getDefault()}</li>
     * </ul>
     *
     * @return default {@code MessageInterpolator} implementation compliant with the
     *         specification
     */
    MessageInterpolator getDefaultMessageInterpolator();

    /**
     * Returns an implementation of the {@link TraversableResolver} interface
     * following the default {@code TraversableResolver} defined in the
     * specification:
     * <ul>
     *     <li>if Java Persistence is available in the runtime environment,
     *     a property is considered reachable if Java Persistence considers
     *     the property as loaded</li>
     *     <li>if Java Persistence is not available in the runtime environment,
     *     all properties are considered reachable</li>
     *     <li>all properties are considered cascadable.</li>
     * </ul>
     *
     * @return default {@code TraversableResolver} implementation compliant with the
     *         specification
     */
    TraversableResolver getDefaultTraversableResolver();

    /**
     * Returns an implementation of the {@link ConstraintValidatorFactory} interface
     * following the default {@code ConstraintValidatorFactory} defined in the
     * specification:
     * <ul>
     *     <li>uses the public no-arg constructor of the {@link ConstraintValidator}</li>
     * </ul>
     *
     * @return default {@code ConstraintValidatorFactory} implementation compliant with the
     *         specification
     */
    ConstraintValidatorFactory getDefaultConstraintValidatorFactory();

    /**
     * Returns an implementation of the {@link ParameterNameProvider}
     * interface following the default {@code ParameterNameProvider}
     * defined in the specification:
     * <ul>
     *     <li>returns names in the form {@code arg&lt;PARAMETER_INDEX&gt;}
     *     where {@code PARAMETER_INDEX} starts at 0 for the first parameter,
     *     e.g. {@code arg0}, {@code arg1} etc.</li>
     * </ul>
     *
     * @return default {@code ParameterNameProvider} implementation compliant with
     *         the specification
     *
     * @since 1.1
     */
    ParameterNameProvider getDefaultParameterNameProvider();

    /**
     * Returns configuration information stored in the {@code META-INF/validation.xml} file.
     * <p/>
     * <b>Note</b>:<br/>
     * Implementations are encouraged to lazily build this object to delay parsing.
     *
     * @return returns an instance of {@link BootstrapConfiguration}; this method never
     *         returns {@code null}; if there is no {@code META-INF/validation.xml} the
     *         different getters of the returned instance will return {@code null}
     *         respectively an empty set or map
     *
     * @since 1.1
     */
    BootstrapConfiguration getBootstrapConfiguration();

    /**
     * Build a {@link ValidatorFactory} implementation.
     *
     * @return the {@code ValidatorFactory}
     * @throws ValidationException if the {@code ValidatorFactory} cannot be built
     */
    ValidatorFactory buildValidatorFactory();
}
/**
 * Represents the user specified default configuration in
 * {@code META-INF/validation.xml}.
 * <p/>
 * Note that modifications to the returned objects do not have any effect.
 * Instead use the methods provided on {@link Configuration} in order to
 * apply modifications to the configuration.
 *
 * @author Emmanuel Bernard
 * @author Gunnar Morling
 * @author Hardy Ferentschik
 * @since 1.1
 */
public interface BootstrapConfiguration {

    /**
     * Class name of the {@link ValidationProvider} implementation
     * or {@code null} if none is specified.
     *
     * @return validation provider class name
     */
    String getDefaultProviderClassName();

    /**
     * Class name of the {@link ConstraintValidatorFactory} implementation
     * or {@code null} if none is specified.
     *
     * @return constraint validator factory class name
     */
    String getConstraintValidatorFactoryClassName();

    /**
     * Class name of the {@link MessageInterpolator} implementation
     * or {@code null} if none is specified.
     *
     * @return message interpolator class name or {@code null}
     */
    String getMessageInterpolatorClassName();

    /**
     * Class name of the {@link TraversableResolver} implementation
     * or {@code null} if none is specified.
     *
     * @return traversable resolver class name or {@code null}
     */
    String getTraversableResolverClassName();

    /**
     * Class name of the {@link ParameterNameProvider} implementation
     * or {@code null} if none is specified.
     *
     * @return parameter name provider class name or {@code null}
     */
    String getParameterNameProviderClassName();

    /**
     * Returns a set of resource paths pointing to XML constraint mapping files.
     * The set is empty if none are specified.
     *
     * @return set of constraint mapping resource paths
     */
    Set<String> getConstraintMappingResourcePaths();

    /**
     * Returns true if the validation execution is explicitly marked as enabled
     * or if it is left undefined.
     *
     * @return whether validation execution is globally enabled
     */
    boolean isExecutableValidationEnabled();

    /**
     * Returns the set of executable types that should be considered
     * unless explicitly overridden via {@link ValidateOnExecution}
     * <p/>
     * Returns a set containing {@link ExecutableType#CONSTRUCTORS} and
     * {@link ExecutableType#NON_GETTER_METHODS} if unspecified in the configuration.
     *
     * @return set of validated executable types
     */
    Set<ExecutableType> getDefaultValidatedExecutableTypes();

    /**
     * Returns properties as a map of string based key/value pairs.
     * The map is empty if no property has been specified.
     *
     * @return the properties map
     */
    Map<String, String> getProperties();
}

A Bean Validation provider must define a sub interface of Configuration uniquely identifying the provider. This subclass is linked to its provider via the ValidationProvider generic parameter. The Configuration sub interface typically hosts provider specific configuration methods.

To facilitate the use of provider specific configuration methods, Configuration uses generics: Configuration<T extends Configuration<T>> ; the generic return type T is returned by chaining methods. The provider specific sub interface must resolve the generic T as itself as shown in Example 5.24, “Example of provider specific Configuration sub interface”.

Example 5.24. Example of provider specific Configuration sub interface

/**
 * Unique identifier of the ACME provider
 * also hosts some provider specific configuration methods
 */
public interface ACMEConfiguration 
    extends Configuration<ACMEConfiguration> {

    /**
     * Enables constraints implementation dynamic reloading when using ACME
     * default to false
     */
    ACMEConfiguration enableDynamicReloading(boolean);

}

When Configuration.buildValidatorFactory() is called, the initialized ValidatorFactory is returned. More specifically, the requested Bean Validation provider is determined and the result of validationProvider.buildValidatorFactory(ConfigurationState) is returned. ConfigurationState gives access to the configuration artifacts defined in META-INF/validation.xml (unless XML configuration is ignored) and provided programmatically to Configuration. Generally speaking, programmatically defined elements have priority over XML defined configuration elements (read the Configuration JavaDoc and see Section 5.5.6, “XML configuration: META-INF/validation.xml” for more information).

Note

A typical implementation of Configuration also implements ConfigurationState, hence this can be passed to buildValidatorFactory(ConfigurationState).

Streams represented in the XML configuration and opened by the Configuration implementation must be closed by the Configuration implementation after the ValidatorFactory creation (or if an exception occurs). Streams provided programmatically are the responsibility of the application.

Example 5.25. ConfigurationState interface

package javax.validation.spi;

/**
 * Contract between a {@link Configuration} and a
 * {@link ValidationProvider} to create a {@link ValidatorFactory}.
 * <p/>
 * The configuration artifacts defined in the XML configuration and provided to the
 * {@code Configuration} are merged and passed along via
 * {@code ConfigurationState}.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 * @author Gunnar Morling
 */
public interface ConfigurationState {

    /**
     * Returns {@code true} if {@link Configuration#ignoreXmlConfiguration()} has been called.
     * <p/>
     * In this case, the {@link ValidatorFactory} must ignore
     * {@code META-INF/validation.xml}.
     *
     * @return {@code true} if {@code META-INF/validation.xml} should be ignored
     */
    boolean isIgnoreXmlConfiguration();

    /**
     * Returns the message interpolator of this configuration.
     * <p/>
     * Message interpolator is defined in the following decreasing priority:
     * <ul>
     *     <li>set via the {@link Configuration} programmatic API</li>
     *     <li>defined in {@code META-INF/validation.xml} provided that
     *     {@code ignoreXmlConfiguration} is false. In this case the instance
     *     is created via its no-arg constructor.</li>
     *     <li>{@code null} if undefined.</li>
     * </ul>
     *
     * @return message interpolator instance or {@code null} if not defined
     */
    MessageInterpolator getMessageInterpolator();

    /**
     * Returns a set of configuration streams.
     * <p/>
     * The streams are defined by:
     * <ul>
     *     <li>mapping XML streams passed programmatically in {@link Configuration}</li>
     *     <li>mapping XML streams located in the resources defined in
     *     {@code META-INF/validation.xml} (constraint-mapping element)</li>
     * </ul>
     * <p/>
     * Streams represented in the XML configuration and opened by the
     * {@code Configuration} implementation must be closed by the
     * {@code Configuration} implementation after the {@link ValidatorFactory}
     * creation (or if an exception occurs). All streams are guaranteed to
     * adhere to the mark/reset contract (see {@link InputStream#markSupported()}
     * by the Bean Validation provider.
     *
     * @return set of input stream
     */
    Set<InputStream> getMappingStreams();

    /**
     * Returns the constraint validator factory of this configuration.
     * <p/>
     * The {@link ConstraintValidatorFactory} implementation is defined in the following
     * decreasing priority:
     * <ul>
     *     <li>set via the {@link Configuration} programmatic API</li>
     *     <li>defined in {@code META-INF/validation.xml} provided that
     *     {@code ignoredXmlConfiguration} is {@code false}. In this case the instance
     *     is created via its no-arg constructor.</li>
     *     <li>{@code null} if undefined.</li>
     * </ul>
     *
     * @return factory instance or {@code null} if not defined
     */
    ConstraintValidatorFactory getConstraintValidatorFactory();

    /**
     * Returns the traversable resolver for this configuration.
     * <p/>
     * {@link TraversableResolver} is defined in the following decreasing priority:
     * <ul>
     *     <li>set via the {@link Configuration} programmatic API</li>
     *     <li>defined in {@code META-INF/validation.xml} provided that
     *     {@code ignoredXmlConfiguration} is {@code false}. In this case the
     *     instance is created via its no-arg constructor.</li>
     *     <li>{@code null} if undefined.</li>
     * </ul>
     *
     * @return traversable resolver instance or {@code null} if not defined
     */
    TraversableResolver getTraversableResolver();

    /**
     * Returns the parameter name provider for this configuration.
     * <p/>
     * {@link ParameterNameProvider} is defined in the following decreasing priority:
     * <ul>
     *     <li>set via the {@link Configuration} programmatic API</li>
     *     <li>defined in {@code META-INF/validation.xml} provided that
     *     {@code ignoreXmlConfiguration} is {@code false}. In this case the instance
     *     is created via its no-arg constructor.</li>
     *     <li>{@code null} if undefined.</li>
     * </ul>
     *
     * @return parameter name provider instance or {@code null} if not defined
     *
     * @since 1.1
     */
    ParameterNameProvider getParameterNameProvider();

    /**
     * Returns a map of non type-safe custom properties.
     * <p/>
     * Properties defined via:
     * <ul>
     *     <li>{@link Configuration#addProperty(String, String)}</li>
     *     <li>{@code META-INF/validation.xml} provided that
     *     {@code ignoreXmlConfiguration}</li> is {@code false}.
     * </ul>
     * <p/>
     * If a property is defined both programmatically and in XML,
     * the value defined programmatically has priority.
     *
     * @return {@code Map} whose key is the property key and the value
     *         the property value
     */
    Map<String, String> getProperties();
}

The requested provider implementation is resolved according to the following rules in the following order:

  • Use the provider implementation requested if Configuration has been created from Validation.byProvider(Class).

  • Use the provider implementation described in the XML configuration (under validation-config.default-provider see Section 5.5.6, “XML configuration: META-INF/validation.xml”) if defined: the value of this element is the fully qualified class name of the ValidationProvider implementation uniquely identifying the provider.

  • Use the first provider implementation returned by validationProviderResolver.getValidationProviders().

The ValidationProviderResolver is specified when Configuration instances are created (see ValidationProvider). If no ValidationProviderResolver instance has been specified, the default ValidationProviderResolver is used.

Configuration instances are provided to the Bean Validation client through the Validation methods. Configuration instances are created by ValidationProvider.

If a problem occurs while building the ValidatorFactory, a ValidationException is raised. This can be due to various reasons including:

  • malformed XML configuration

  • malformed XML mapping

  • inability to find the provider (or a provider)

  • inability to instantiate extension classes provided in the XML configuration

  • inconsistent XML mapping (entity declared more than once, incorrect field etc.)

  • invalid constraint declaration or definition

Other exception causes may occur.

Here is an example of Configuration use.

Example 5.26. Use Configuration

Configuration<?> configuration = [...];
ValidatorFactory factory = configuration
              .messageInterpolator( new WBMessageInterpolator() )
              .traversableResolver( new JPAAwareTraversableResolver() )
              .buildValidatorFactory();

The following shows an example of setting up a Configuration, retrieving a validator factory from it, subsequently altering the configuration and then retrieving another factory:

Example 5.27. Using Configuration to create several validator factories

Configuration<?> configuration = [...];
ValidatorFactory factory1 = configuration
              .messageInterpolator( new WBMessageInterpolator() )
              .buildValidatorFactory();

ValidatorFactory factory2 = configuration
              .traversableResolver( new JPAAwareTraversableResolver() )
              .buildValidatorFactory();

Here, factory1 is set up using a custom message interpolator, while factory2 is set up using the same message interpolator and additionally using a custom traversable resolver.

5.5.4. ValidationProvider and ValidationProviderResolver

ValidationProvider is the contract between the bootstrap process and a specific Bean Validation provider. ValidationProviderResolver implements the discovery mechanism for Bean Validation provider implementations. Any Bean Validation client can implement such a discovery mechanism but it is typically implemented by containers having specific classloader structures and restrictions.

5.5.4.1. ValidationProviderResolver

ValidationProviderResolver returns the list of Bean Validation providers available at runtime and more specifically a ValidationProvider instance for each provider available in the context. This service can be customized by implementing ValidationProviderResolver. Implementations must be thread-safe.

Example 5.28. ValidationProviderResolver

/**
 * Determines the list of Bean Validation providers available in the runtime environment
 * <p/>
 * Bean Validation providers are identified by the presence of
 * {@code META-INF/services/javax.validation.spi.ValidationProvider}
 * files following the Service Provider pattern described
 * <a href="http://docs.oracle.com/javase/6/docs/technotes/guides/jar/jar.html#Service%20Provider">here</a>.
 * <p/>
 * Each {@code META-INF/services/javax.validation.spi.ValidationProvider} file contains the list of
 * {@link ValidationProvider} implementations each of them representing a provider.
 * <p/>
 * Implementations must be thread-safe.
 *
 * @author Emmanuel Bernard
 */
public interface ValidationProviderResolver {

    /**
     * Returns a list of {@link ValidationProvider} available in the runtime environment.
     *
     * @return list of validation providers
     */
    List<ValidationProvider<?>> getValidationProviders();
}

By default, providers are resolved using the Service Provider pattern described in http://docs.oracle.com/javase/6/docs/technotes/guides/jar/jar.html#Service%20Provider. Bean Validation providers must supply a service provider configuration file by creating a text file javax.validation.spi.ValidationProvider and placing it in the META-INF/services directory of one of its jar files. The content of the file contains the name of the provider implementation class of the javax.validation.spi.ValidationProvider interface.

Bean Validation provider jars may be installed or made available in the same ways as other service providers, e.g. as extensions or added to the application classpath according to the guidelines in the JAR file specification.

The default ValidationProviderResolver implementation will locate all the Bean Validation providers by their provider configuration files visible in the classpath. The default ValidationProviderResolver implementation is recommended and custom ValidationProviderResolver implementations should be rarely used. A typical use of a custom resolution is resolving providers in a classloader constrained container like OSGi or in a tool environment (IDE).

The default ValidationProviderResolver can be accessed via BootStrapState.getDefaultValidationProviderResolver(). This method is typically used by the Bean Validation provider Configuration implementation.

5.5.4.2. ValidationProvider

ValidationProvider represents the SPI (Service Provider Interface) defining the contract between the provider discovery and initialization mechanism, and the provider. A ValidationProvider does:

  • Provide a generic Configuration implementation (i.e. not tied to a given provider).

  • Provide a provider specific Configuration implementation. This Configuration will specifically build ValidatorFactory instances of the provider it comes from.

  • Build a ValidatorFactory object from the configuration provided by ConfigurationState.

Example 5.29. ValidationProvider

package javax.validation.spi;

/**
 * Contract between the validation bootstrap mechanism and the provider engine.
 * <p/>
 * Implementations must have a public no-arg constructor. The construction of a provider
 * should be as "lightweight" as possible.
 *
 * {@code T} represents the provider specific Configuration subclass
 * which typically host provider's additional configuration methods.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 */
public interface ValidationProvider<T extends Configuration<T>> {

    /**
     * Returns a {@link Configuration} instance implementing {@code T},
     * the {@code Configuration} sub-interface.
     * The returned {@code Configuration} instance must use the current provider
     * ({@code this}) to build the {@code ValidatorFactory} instance.
     *
     * @param state bootstrap state
     * @return specific {@code Configuration} implementation
     */
    T createSpecializedConfiguration(BootstrapState state);

    /**
     * Returns a {@link Configuration} instance. This instance is not bound to
     * use the current provider. The choice of provider follows the algorithm described
     * in {@code Configuration}
     * <p/>
     * The {@link ValidationProviderResolver} used by {@code Configuration}
     * is provided by {@code state}.
     * If null, the default {@code ValidationProviderResolver} is used.
     *
     * @param state bootstrap state
     * @return non specialized Configuration implementation
     */
    Configuration<?> createGenericConfiguration(BootstrapState state);

    /**
     * Build a {@link ValidatorFactory} using the current provider implementation.
     * <p/>
     * The {@code ValidatorFactory} is assembled and follows the configuration passed
     * via {@link ConfigurationState}.
     * <p/>
     * The returned {@code ValidatorFactory} is properly initialized and ready for use.
     *
     * @param configurationState the configuration descriptor
     * @return the instantiated {@code ValidatorFactory}
     * @throws ValidationException if the {@code ValidatorFactory} cannot be built
     */
    ValidatorFactory buildValidatorFactory(ConfigurationState configurationState);
}

Example 5.30. BootstrapState interface

package javax.validation.spi;

/**
 * Defines the state used to bootstrap the {@link Configuration}.
 *
 * @author Emmanuel Bernard
 * @author Sebastian Thomschke 
 */
public interface BootstrapState {

    /**
     * User defined {@code ValidationProviderResolver} strategy
     * instance or {@code null} if undefined.
     *
     * @return ValidationProviderResolver instance or null
     */
    ValidationProviderResolver getValidationProviderResolver();

    /**
     * Specification default {@code ValidationProviderResolver}
     * strategy instance.
     * 
     * @return default implementation of ValidationProviderResolver
     */
    ValidationProviderResolver getDefaultValidationProviderResolver();
}

A client can request a specific Bean Validation provider by using <T extends Configuration<T>, U extends ValidationProvider<T>> Validation.byProvider(Class<U>) or by defining the provider in the XML configuration file. The key uniquely identifying a Bean Validation provider is the ValidationProvider implementation specific to this provider.

A ValidationProvider implementation is linked (via its generic parameter) to a specific sub interface of Configuration. The Bean Validation bootstrap API makes use of this link to return the specific Configuration subinterface implementation in a type-safe way when a specific provider is requested. The sub interface does not have to add any new method but is the natural holder for provider specific configuration methods.

Example 5.31. Example of provider specific Configuration sub interface

/**
 * Unique identifier of the ACME provider
 * also hosts some provider specific configuration methods
 */
public interface ACMEConfiguration 
    extends Configuration<ACMEConfiguration> {

    /**
     * Enables constraints implementation dynamic reloading when using ACME
     * default to false
     */
    ACMEConfiguration enableDynamicReloading(boolean);

}

/**
 * ACME validation provider
 * Note how ACMEConfiguration and ACMEProvider are linked together 
 * via the generic parameter.
 */
public class ACMEProvider implements ValidationProvider<ACMEConfiguration> {
    [...]
}

Note

Configuration references itself in the generic definition. Methods of Configuration will return the ACMEConfiguration making the API easy to use even for vendor specific extensions.

The provider discovery mechanism uses the following algorithm:

  • Retrieve available providers using ValidationProviderResolver.getValidationProviders().

  • The first ValidationProvider matching the requested provider is returned. Providers are evaluated in the order they are returned by ValidationProviderResolver. A provider instance is considered matching if it is assignable to the requested provider class.

When the default Bean Validation provider is requested, the first ValidationProvider returned by the ValidationProviderResolver strategy is returned.

Every Bean Validation provider must provide a ValidationProvider implementation containing a public no-arg constructor and add the corresponding META-INF/services/javax.validation.spi.ValidationProvider file descriptor in one of its jars.

If a problem occurs while building the ValidatorFactory, a ValidationException is raised. This can be due to various reasons including:

  • malformed XML mapping

  • inability to find the provider (or a provider)

  • inability to instantiate extension classes provided in the XML configuration

  • inconsistent XML mapping (entity declared more than once, incorrect field etc.)

  • invalid constraint declaration or definition

5.5.5. Validation

The Validation class is the entry point used to bootstrap Bean Validation providers. The first entry point, buildDefaultValidatorFactory(), is considered to be the default ValidatorFactory and is equivalent to the ValidatorFactory returned by Validation.byDefaultProvider().configure().buildValidatorFactory().

Example 5.32. Validation methods available

/**
 * This class is the entry point for Bean Validation.
 * <p/>
 * There are three ways to bootstrap it:
 * <ul>
 *     <li>The easiest approach is to build the default {@link ValidatorFactory}.
 *     <pre>
 * ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
 * </pre>
 *     In this case, the default validation provider resolver
 *     will be used to locate available providers.
 *     <p/>
 *     The chosen provider is defined as followed:
 *     <ul>
 *         <li>if the XML configuration defines a provider, this provider is used</li>
 *         <li>if the XML configuration does not define a provider or if no XML
 *         configuration is present the first provider returned by the
 *         {@link ValidationProviderResolver} instance is used.</li>
 *     </ul>
 *     </li>
 *     <li>
 *     The second bootstrap approach allows to choose a custom
 *     {@code ValidationProviderResolver}. The chosen
 *     {@link ValidationProvider} is then determined in the same way
 *     as in the default bootstrapping case (see above).
 *     <pre>
 * Configuration<?> configuration = Validation
 *    .byDefaultProvider()
 *    .providerResolver( new MyResolverStrategy() )
 *    .configure();
 * ValidatorFactory factory = configuration.buildValidatorFactory();
 * </pre>
 *     </li>
 *     <li>
 *     The third approach allows you to specify explicitly and in
 *     a type safe fashion the expected provider.
 *     <p/>
 *     Optionally you can choose a custom {@code ValidationProviderResolver}.
 *     <pre>
 * ACMEConfiguration configuration = Validation
 *    .byProvider(ACMEProvider.class)
 *    .providerResolver( new MyResolverStrategy() )  // optionally set the provider resolver
 *    .configure();
 * ValidatorFactory factory = configuration.buildValidatorFactory();
 * </pre>
 *     </li>
 * </ul>
 * <p/>
 * Note:
 * <ul>
 *     <li>
 *     The {@code ValidatorFactory} object built by the bootstrap process should be cached
 *     and shared amongst {@code Validator} consumers.
 *     </li>
 *     <li>This class is thread-safe.</li>
 * </ul>
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 */
public class Validation {

    /**
     * Builds and returns a {@link ValidatorFactory} instance based on the
     * default Bean Validation provider and following the XML configuration.
     * <p/>
     * The provider list is resolved using the default validation provider resolver
     * logic.
     * <p/>
     * The code is semantically equivalent to
     * {@code Validation.byDefaultProvider().configure().buildValidatorFactory()}.
     *
     * @return {@code ValidatorFactory} instance
     *
     * @throws ValidationException if the {@code ValidatorFactory} cannot be built
     */
    public static ValidatorFactory buildDefaultValidatorFactory() {
        [...]
    }

    /**
     * Builds a {@link Configuration}. The provider list is resolved
     * using the strategy provided to the bootstrap state.
     * <pre>
     * Configuration&lt?&gt; configuration = Validation
     *    .byDefaultProvider()
     *    .providerResolver( new MyResolverStrategy() )
     *    .configure();
     * ValidatorFactory factory = configuration.buildValidatorFactory();
     * </pre>
     * The provider can be specified in the XML configuration. If the XML
     * configuration does not exist or if no provider is specified,
     * the first available provider will be returned.
     *
     * @return instance building a generic {@code Configuration}
     *         compliant with the bootstrap state provided
     */
    public static GenericBootstrap byDefaultProvider() {
        [...]
    }

    /**
     * Builds a {@link Configuration} for a particular provider implementation.
     * <p/>
     * Optionally overrides the provider resolution strategy used to determine the provider.
     * <p/>
     * Used by applications targeting a specific provider programmatically.
     * <p/>
     * <pre>
     * ACMEConfiguration configuration =
     *     Validation.byProvider(ACMEProvider.class)
     *             .providerResolver( new MyResolverStrategy() )
     *             .configure();
     * </pre>,
     * where {@code ACMEConfiguration} is the
     * {@code Configuration} sub interface uniquely identifying the
     * ACME Bean Validation provider. and {@code ACMEProvider} is the
     * {@link ValidationProvider} implementation of the ACME provider.
     *
     * @param providerType the {@code ValidationProvider} implementation type
     *
     * @return instance building a provider specific {@code Configuration}
     *         sub interface implementation
     */
    public static <T extends Configuration<T>, U extends ValidationProvider<T>>
    ProviderSpecificBootstrap<T> byProvider(Class<U> providerType) {
        [...]
    }

    [...]
}

The second entry point lets the client provide a custom ValidationProviderResolution instance. This instance is passed to GenericBootstrap. GenericBootstrap builds a generic Configuration using the first ValidationProvider returned by ValidationProviderResolution and calling ValidationProvider.createGenericConfiguration(BootstrapState state). BootstrapState holds the ValidationProviderResolution instance passed to GenericBootstrap and will be used by the Configuration instance when resolving the provider to use. Note that ValidationProvider.createGenericConfiguration returns a Configuration object not bound to any particular provider.

Example 5.33. GenericBootstrap interface

package javax.validation.bootstrap;

/**
 * Defines the state used to bootstrap Bean Validation and
 * creates a provider agnostic {@link Configuration}.
 *
 * @author Emmanuel Bernard
 */
public interface GenericBootstrap {

    /**
     * Defines the provider resolution strategy.
     * This resolver returns the list of providers evaluated
     * to build the {@link Configuration}.
     * <p/>
     * If no resolver is defined, the default {@link ValidationProviderResolver}
     * implementation is used.
     *
     * @param resolver the {@code ValidationProviderResolver} to use for bootstrapping
     * @return {@code this} following the chaining method pattern
     */
    GenericBootstrap providerResolver(ValidationProviderResolver resolver);

    /**
     * Returns a generic {@link Configuration} implementation.
     * At this stage the provider used to build the {@link ValidatorFactory}
     * is not defined.
     * <p/>
     * The {@code Configuration} implementation is provided by the first provider
     * returned by the {@link ValidationProviderResolver} strategy.
     *
     * @return a {@code Configuration} implementation compliant with the bootstrap state
     * @throws ValidationException if the {@code Configuration} object cannot be built;
     *         this is generally due to an issue with the {@code ValidationProviderResolver}
     */
    Configuration<?> configure();
}

The last entry point lets the client define the specific Bean Validation provider requested as well as a custom ValidationProviderResolver implementation if needed. The entry point method, Validation.byProvider(Class<U> providerType), takes the provider specific ValidationProvider implementation type and returns a ProviderSpecificBootstrap object that guarantees to return an instance of the specific Configuration sub interface. Thanks to the use of generics, the client API does not have to cast to the Configuration sub interface.

A ProviderSpecificBootstrap object can optionally receive a ValidationProviderResolver instance.

Example 5.34. ProviderSpecificBootstrap interface

package javax.validation.bootstrap;

/**
 * Defines the state used to bootstrap Bean Validation and
 * creates a provider specific {@link Configuration}
 * of type {@code T}.
 * <p/>
 * The specific {@code Configuration} is linked to the provider via the generic
 * parameter of the {@link ValidationProvider} implementation.
 * <p/>
 * The requested provider is the first provider instance assignable to
 * the requested provider type (known when {@link ProviderSpecificBootstrap} is built).
 * The list of providers evaluated is returned by {@link ValidationProviderResolver}.
 * If no {@code ValidationProviderResolver} is defined, the
 * default {@code ValidationProviderResolver} strategy is used.
 *
 * @author Emmanuel Bernard
 */
public interface ProviderSpecificBootstrap<T extends Configuration<T>> {

    /**
     * Optionally defines the provider resolver implementation used.
     * If not defined, use the default {@link ValidationProviderResolver}
     *
     * @param resolver {@code ValidationProviderResolver} implementation used
     *
     * @return {@code this} following the chaining method pattern
     */
    public ProviderSpecificBootstrap<T> providerResolver(ValidationProviderResolver resolver);

    /**
     * Determines the provider implementation suitable for {@code T} and delegates
     * the creation of this specific {@link Configuration} subclass to the provider.
     *
     * @return {@code Configuration} sub interface implementation
     *
     * @throws ValidationException if the {@code Configuration} object cannot be built;
     *         this is generally due to an issue with the {@code ValidationProviderResolver}
     */
    public T configure();
}

ProviderSpecificBootstrap.configure() must return the result of ValidationProvider.createSpecializedConfiguration(BootstrapState state). The state parameter holds the ValidationProviderResolver passed to ProviderSpecificBootstrap. The validation provider instance used is the one assignable to the type passed as a parameter in Validation.byProvider(Class). The validation provider is selected according to the algorithm described in (Section 5.5.4.2, “ValidationProvider”).

The Validation implementation must not contain any non private attribute or method aside from the three public static bootstrap methods:

  • public static ValidatorFactory buildDefaultValidatorFactory()

  • public static GenericBootstrap byDefaultProvider()

  • public static <T extends Configuration<T>, U extends ValidationProvider<T>> ProviderSpecificBootstrap<T> byProvider(Class<U> providerType)

The bootstrap API is designed to allow complete portability amongst Bean Validation provider implementations. The bootstrap implementation must ensure it can bootstrap third party providers.

When bootstrapping a Bean Validation provider, if the ValidationProviderResolver either fails or if the expected provider is not found, a ValidationException is raised.

5.5.6. XML configuration: META-INF/validation.xml

Unless explicitly ignored by calling Configuration.ignoreXMLConfiguration(), a Configuration takes into account the configuration available in META-INF/validation.xml. This configuration file is optional but can be used by applications to refine some of the Bean Validation behavior. If more than one META-INF/validation.xml file is found in the classpath, a ValidationException is raised.

Implementations supporting Bean Validation 1.1 must properly parse deployment descriptors of Bean Validation 1.0 and 1.1.

Unless stated otherwise, XML based configuration settings are overridden by values explicitly set via the Configuration API. For example, the MessageInterpolator defined via Configuration.messageInterpolator(MessageInterpolator) has priority over the message-interpolator definition.

default-provider: represents the class name of the provider specific ValidationProvider implementation class. If defined, the specific provider is used (unless a specific provider has been chosen via the programmatic approach).

message-interpolator: represents the fully qualified class name of the MessageInterpolator implementation. When defined in XML, the implementation must have a public no-arg constructor.

traversable-resolver: represents the fully qualified class name of the TraversableResolver implementation. When defined in XML, the implementation must have a public no-arg constructor.

constraint-validator-factory: represents the fully qualified class name of the ConstraintValidatorFactory implementation. When defined in XML, the implementation must have a public no-arg constructor.

parameter-name-provider: represents the fully qualified class name of the ParameterNameProvider implementation. When defined in XML, the implementation must have a public no-arg constructor.

executable-validation: allows to disable executable validation entirely via its attribute enabled="false" and optionally contains default-validated-executable-types. enabled defaults to true.

default-validated-executable-types: declared under executable-validation, contains the list of executable-type that are considered by default by the integration technology validating executables upon execution.

constraint-mapping: represents the resource path of an XML mapping file. More than one constraint-mapping element can be present. Mappings provided via Configuration.addMapping(InputStream) are added to the list of mappings described via constraint-mapping.

property: represents a key/value pair property providing room to provider specific configurations. Vendors should use vendor namespaces for properties (e.g., com.acme.validation.logging). Entries that make use of the namespace javax.validation and its subnamespaces must not be used for vendor-specific information. The namespace javax.validation is reserved for use by this specification. Properties defined via Configuration.addProperty(String, String) are added to the properties defined via property. If a property with the same name are defined in both XML and via the programmatic API, the value provided via programmatic API has priority.

All these top level elements are optional.

If a public no-arg constructor is missing on any of the classes referenced by the relevant XML elements, a ValidationException is raised during the Configuration.buildValidatorFactory() call.

Example 5.35. Example of META-INF/validation.xml file

<?xml version="1.0" encoding="UTF-8"?>
<validation-config
        xmlns="http://jboss.org/xml/ns/javax/validation/configuration"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/configuration validation-configuration-1.1.xsd"
        version="1.1">
    <default-provider>com.acme.ACMEProvider</default-provider>
    <message-interpolator>com.acme.ACMEAwareMessageInterpolator</message-interpolator>

    <executable-validation>
        <default-validated-executable-types>
            <executable-type>NONE</executable-type>
        </default-validated-executable-types>
    </executable-validation>

    <constraint-mapping>META-INF/validation/order-constraints.xml</constraint-mapping>
    <constraint-mapping>META-INF/validation/catalog-constraints.xml</constraint-mapping>
    <constraint-mapping>META-INF/validation/customer-constraints.xml</constraint-mapping>

    <property name="com.acme.validation.logging">WARN</property>
    <property name="com.acme.validation.safetyChecking">failOnError</property>

</validation-config>

The XML schema is described in Section 8.2, “Configuration schema”.

5.5.7. Bootstrapping considerations

The Bean Validation bootstrap API can be used directly by any application or made available through a container or other framework. In all cases, the following rules apply:

  • ValidatorFactory is a thread-safe object that should be built once per deployment unit

  • ValidatorFactory should be closed when it is no longer needed (e.g. when the unit is undeployed or the server stopped).

  • Validator is a thread-safe and lightweight object which can be cached by the ValidatorFactory instance.

Chapter 6. Constraint metadata request APIs

The Bean Validation specification provides a way to query the constraint repository. This API is expected to be used for tooling support as well as integration with other frameworks, libraries and JSRs. The Bean Validation specification aims to provide both a validation engine and a metadata repository for object constraints. Frameworks (EE or SE) in need for constraint definition, validation and metadata will be able to rely on the Bean Validation specification for these services avoiding any unnecessary duplication work from an application and infrastructure point of view.

6.1. Validator

The main API to access all metadata related to a given object is Validator (see Section 5.5, “Bootstrapping” for more information on how to retrieve a Validator instance).

A Validator instance hosts the method to access to the metadata repository for a given class. It is recommended to leave the caching of Validator instances to the ValidatorFactory. Validator implementations are thread-safe.

Example 6.1. Validator interface (metadata request API)

/**
 * Validates bean instances. Implementations of this interface must be thread-safe.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 * @author Gunnar Morling
 */
public interface Validator {

    [...] //See 5.1

    /**
     * Returns the descriptor object describing bean constraints.
     * <p/>
     * The returned object (and associated objects including
     * {@link ConstraintDescriptor}s) are immutable.
     *
     * @param clazz class or interface type evaluated
     * @return the bean descriptor for the specified class
     * @throws IllegalArgumentException if clazz is {@code null}
     * @throws ValidationException if a non recoverable error happens
     *         during the metadata discovery or if some
     *         constraints are invalid.
     */
    BeanDescriptor getConstraintsForClass(Class<?> clazz);
}

getConstraintsForClass() returns a BeanDescriptor object describing the bean level constraints (see Section 4.1.1, “Object validation”) and providing access to the property level constraints metadata. An IllegalArgumentException is raised if the clazz parameter is null.

If a constraint definition or declaration hosted by the requested class (or any of it's superclasses and interfaces according to the constraint propagation rules) is invalid, a ValidationException is raised. This can be a subclass of ValidationException like ConstraintDefinitionException, ConstraintDeclarationException or UnexpectedTypeException.

All descriptor types accessible via getConstraintsForClass() and introduced in the following sections are located in the package javax.validation.metadata.

6.2. ElementDescriptor

ElementDescriptor is the root interface describing elements hosting constraints. It is used to describe the list of constraints for a given element (whether it be a class, property, method etc.).

Example 6.2. ElementDescriptor interface

package javax.validation.metadata;

/**
 * Describes a validated element (class, property, method etc.).
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 * @author Gunnar Morling
 */
public interface ElementDescriptor {

    /**
     * @return returns {@code true} if at least one constraint declaration is present
     *         for this element in the class hierarchy, {@code false} otherwise
     */
    boolean hasConstraints();

    /**
     * @return the statically defined returned type
     */
    Class<?> getElementClass();

    /**
     * Returns all constraint descriptors for this element in the class hierarchy
     * or an empty {@code Set} if none are present.
     *
     * @return {@code Set} of constraint descriptors for this element
     */
    Set<ConstraintDescriptor<?>> getConstraintDescriptors();

    /**
     * Finds constraints and potentially restricts them to certain criteria.
     *
     * @return {@code ConstraintFinder} object
     */
    ConstraintFinder findConstraints();

    /**
     * Declares restrictions on retrieved constraints.
     * Restrictions are cumulative.
     * <p/>
     * A {@code ConstraintFinder} is not thread-safe. The set of matching
     * {@link ConstraintDescriptor} is.
     */
    interface ConstraintFinder {

        /**
         * Restricts to the constraints matching a given set of groups for this element.
         * <p/>
         * This method respects group conversion, group sequences
         * and group inheritance (including class-level {@link Default} group
         * overriding) but does not return {@link ConstraintDescriptor}s
         * in any particular order.
         * Specifically, ordering of the group sequence is not respected.
         *
         * @param groups groups targeted
         * @return {@code this} following the chaining method pattern
         */
        ConstraintFinder unorderedAndMatchingGroups(Class<?>... groups);

        /**
         * Restricts to the constraints matching the provided scope for this element.
         *
         * Defaults to {@link Scope#HIERARCHY}
         *
         * @param scope expected scope
         * @return {@code this} following the chaining method pattern
         */
        ConstraintFinder lookingAt(Scope scope);

        /**
         * Restricts to the constraints hosted on the listed {@code types}
         * for a given element.
         * <p/>
         * Defaults to all possible types of the element.
         * <p/>
         * Typically used to restrict to fields ({@code FIELD})
         * or getters ({@code METHOD}).
         *
         * @param types targeted types
         *
         * @return {@code this} following the chaining method pattern
         */
        ConstraintFinder declaredOn(ElementType... types);

        /**
         * Retrieves the constraint descriptors following the defined
         * restrictions and hosted on the element described by
         * {@link ElementDescriptor}.
         *
         * @return matching constraint descriptors
         */
        Set<ConstraintDescriptor<?>> getConstraintDescriptors();

        /**
         * Returns {@code true} if at least one constraint declaration
         * matching the restrictions is present on the element,
         * {@code false} otherwise.
         *
         * @return {@code true} if there is at least one constraint
         */
        boolean hasConstraints();
    }
}
package javax.validation.metadata;

/**
 * Scope looked at when discovering constraints.
 *
 * @author Emmanuel Bernard
 */
public enum Scope {

    /**
     * Look for constraints declared on the current class element
     * and ignore inheritance and elements with the same name in
     * the class hierarchy.
     */
    LOCAL_ELEMENT,

    /**
     * Look for constraints declared on all elements of the class hierarchy
     * with the same name.
     */
    HIERARCHY
}

getElementClass() returns

  • the object type when invoked on BeanDescriptor,

  • the type of a property or parameter when invoked on PropertyDescriptor or ParameterDescriptor respectively,

  • Object[].class when invoked on CrossParameterDescriptor,

  • the return type when invoked on ConstructorDescriptor, MethodDescriptor or ReturnValueDescriptor.

getConstraintDescriptors() returns all the ConstraintDescriptors (see Section 6.11, “ConstraintDescriptor”) hosted on the given element in the class hierarchy, each ConstraintDescriptor describing one of the constraints declared on the given element.

hasConstraints() returns true if the given element in the class hierarchy holds at least one constraint declaration.

If you need to query the metadata API in a more fine grained way for example by restricting the constraints to the one described on fields or on getters or by restricting to a given set of groups, you can use the ConstraintFinder fluent API by calling findConstraints().

unorderedAndMatchingGroups() restricts the results to the ConstraintDescriptors (see Section 6.11, “ConstraintDescriptor”) matching the given groups. Order is not respected but group inheritance and inheritance via sequence (including the Default group overriding at the class level) are honored.

declaredOn() lets you restrict the list of element types constraints are hosted on. This is particularly useful to retrieve property constraints only hosted on fields (ElementType.FIELD) or only hosted on getters (ElementType.METHOD).

lookingAt() lets you restrict which constraints are considered. Either constraints belonging to the element but hosted on the class represented by the given descriptor (Scope.LOCAL_ELEMENT), or constraints belonging to the element but hosted anywhere in the class hierarchy (Scope.HIERARCHY).

Here is an example restricting the list of constraints on getters, matching the default group and declared physically on the name getter of Customer (and not any of the getters on the super classes).

Example 6.3. Using the fluent API to restrict matching constraints

public class User {

    @Size(max=50) 
    String getName() {
        [...]
    }

    [...]
}

public class Customer extends User {

    @NotNull
    String getName() {
        [...]
    }
}

PropertyDescriptor pd = 
    validator.getConstraintsForClass(Customer.class).getConstraintsForProperty("name");
Set<ConstraintDescriptor<?>> constraints = 
    pd.findConstraints()
        .declaredOn(ElementType.METHOD)
        .unorderedAndMatchingGroups(Default.class)
        .lookingAt(Scope.LOCAL_ELEMENT)
        .getConstraintDescriptors();

assert 1 == constraints.size();

constraints = pd.getConstraintDescriptors();
//equivalent to pd.findConstraints().getConstraintDescriptors();
assert 2 == constraints.size();

The following example shows how the fluent API is used to retrieve parameter, cross-parameter and return value constraints, taking into account locally declared constraints as well as constraints declared in the inheritance hierarchy.

Example 6.4. Using the fluent API to select method and constructor constraints

public class User {

    public User(@Size(max=50) String name) {
        [...]
    }

    @PasswordParametersMatch
    @NotNull
    public String resetPassword(
        @NotNull @Size(min=8) String password,
        @NotNull @Size(min=8) String confirmation) {
        [...]
    }
}

public class Customer extends User {

    public Customer(@NotNull String name) {
        [...]
    }

    @Size(min=8)
    public String resetPassword(String password, String confirmation) {
        [...]
    }
}

MethodDescriptor methodDescriptor = validator
    .getConstraintsForClass( Customer.class )
    .getConstraintsForMethod( "resetPassword", String.class, String.class );

//one cross-parameter constraint
assert 1 == methodDescriptor.getCrossParameterDescriptor().getConstraintDescriptors().size();

//one local return value constraint
assert 1 == methodDescriptor.getReturnValueDescriptor()
    .findConstraints()
    .lookingAt( Scope.LOCAL_ELEMENT )
    .getConstraintDescriptors()
    .size();

//two return value constraints in the complete hierarchy
assert 2 == methodDescriptor.getReturnValueDescriptor()
    .findConstraints()
    .lookingAt( Scope.HIERARCHY )
    .getConstraintDescriptors()
    .size();

//two parameter constraints, defined on overridden method
assert 2 == methodDescriptor.getParameterDescriptors()
    .get( 0 )
    .getConstraintDescriptors()
    .size();

ConstructorDescriptor constructorDescriptor = validator
    .getConstraintsForClass( Customer.class )
    .getConstraintsForConstructor( String.class );

//one parameter constraint; constraints from super constructor don't apply
assert 1 == constructorDescriptor.getParameterDescriptors()
    .get( 0 )
    .findConstraints()
    .lookingAt( Scope.HIERARCHY )
    .getConstraintDescriptors()
    .size();

6.3. BeanDescriptor

The BeanDescriptor interface describes a constrained Java Bean. This interface is returned by Validator.getConstraintsForClass(Class<?>).

Example 6.5. BeanDescriptor interface

package javax.validation.metadata;

/**
 * Describes a constrained Java Bean and the constraints associated to it. All
 * objects returned by the methods of this descriptor (and associated objects
 * including {@link ConstraintDescriptor}s) are immutable.
 *
 * @author Emmanuel Bernard
 * @author Gunnar Morling
 */
public interface BeanDescriptor extends ElementDescriptor {

    /**
     * Returns {@code true} if the bean involves validation:
     * <ul>
     *     <li>a constraint is hosted on the bean itself</li>
     *     <li>a constraint is hosted on one of the bean properties</li>
     *     <li>or a bean property is marked for cascaded validation ({@link Valid})</li>
     * </ul>
     * <p/>
     * Constrained methods and constructors are ignored.
     *
     * @return {@code true} if the bean involves validation, {@code false} otherwise
     */
    boolean isBeanConstrained();

    /**
     * Returns the property descriptor for a given property.
     * <p/>
     * Returns {@code null} if the property does not exist or has no
     * constraint nor is marked as cascaded (see {@link #getConstrainedProperties()})
     * Properties of super types are considered.
     *
     * @param propertyName property evaluated
     * @return the property descriptor for a given property
     * @throws IllegalArgumentException if {@code propertyName} is {@code null}
     */
    PropertyDescriptor getConstraintsForProperty(String propertyName);

    /**
     * Returns a set of property descriptors having at least one constraint defined
     * or marked as cascaded ({@link Valid}).
     * <p/>
     * If not property matches, an empty set is returned.
     * Properties of super types are considered.
     *
     * @return the set of {@link PropertyDescriptor}s for the constraint properties; if
     *         there are no constraint properties, the empty set is returned
     */
    Set<PropertyDescriptor> getConstrainedProperties();

    /**
     * Returns a method descriptor for the given method.
     * <p/>
     * Returns {@code null} if no method with the given name and parameter types
     * exists or the specified method neither has parameter or return value constraints nor a parameter
     * or return value marked for cascaded validation.
     * Methods of super types are considered.
     *
     * @param methodName the name of the method
     * @param parameterTypes the parameter types of the method
     * @return a method descriptor for the given method
     * @throws IllegalArgumentException if {@code methodName} is {@code null}
     *
     * @since 1.1
     */
    MethodDescriptor getConstraintsForMethod(String methodName, Class<?>... parameterTypes);

    /**
     * Returns a set with descriptors for the constrained methods of the bean
     * represented by this descriptor.
     * <p/>
     * Constrained methods have at least one parameter or return value constraint
     * or at least one parameter or return value marked for cascaded validation.
     * Methods of super types are considered.
     * <p/>
     * Only methods matching the given method type(s) are considered.
     *
     * @param methodType method type to consider
     * @param methodTypes remaining optional method types to consider
     * @return a set with descriptors for the constrained methods of this bean;
     *         will be empty if this bean has no constrained methods of the considered
     *         method type(s) but never {@code null}
     *
     * @since 1.1
     */
    Set<MethodDescriptor> getConstrainedMethods(MethodType methodType, MethodType... methodTypes);

    /**
     * Returns a constructor descriptor for the given constructor.
     * <p/>
     * Returns {@code null} if no constructor with the given parameter types
     * exists or the specified constructor neither has parameter or return value
     * constraints nor a parameter or return value marked for cascaded
     * validation.
     * Constructor of super types are considered.
     *
     * @param parameterTypes the parameter types of the constructor
     * @return a constructor descriptor for the given constructor
     *
     * @since 1.1
     */
    ConstructorDescriptor getConstraintsForConstructor(Class<?>... parameterTypes);

    /**
     * Returns a set with descriptors for the constrained constructors of the
     * bean represented by this descriptor.
     * <p/>
     * Constrained constructors have at least one parameter or return value constraint
     * or at least one parameter or return value marked for cascaded validation.
     *
     * @return a set with descriptors for the constrained constructor of this
     *         bean; will be empty if this bea has no constrained constructor
     *         but never {@code null}
     *
     * @since 1.1
     */
    Set<ConstructorDescriptor> getConstrainedConstructors();
}

Example 6.6. MethodType

package javax.validation.metadata;

/**
 * Represents the type of a method: getter or non getter.
 *
 * @author Emmanuel Bernard <emmanuel@hibernate.org>
 * @since 1.1
 */
public enum MethodType {

    /**
     * A method following the getter pattern. A getter according to the
     * JavaBeans specification is a method whose:
     * <ul>
     *     <li>name starts with get, has a return type but no parameter</li>
     *     <li>name starts with is, has a return type and is returning {@code boolean}.</li>
     * </ul>
     */
    GETTER,

    /**
     * A method that does not follow the getter pattern. A getter according to the
     * JavaBeans specification is a method whose:
     * <ul>
     *     <li>name starts with get, has a return type but no parameter</li>
     *     <li>name starts with is, has a return type and is returning {@code boolean}.</li>
     * </ul>
     */
    NON_GETTER
}

isBeanConstrained() returns true if the given class (and superclasses and interfaces) has at least one class-level or property-level constraint or validation cascade. If the method returns false, the Bean Validation engine can safely ignore the bean as it will not be impacted by validation.

getConstraintsForProperty() returns a PropertyDescriptor object describing the property level constraints (See Section 4.1.2, “Field and property validation”). The property is uniquely identified by its name as per the JavaBeans convention: field level and getter level constraints of the given name are all returned. An IllegalArgumentException is raised if the propertyName parameter is null.

getConstrainedProperties() returns the PropertyDescriptors of the bean properties having at least one constraint or being cascaded (@Valid annotation).

getConstraintsForMethod() returns a MethodDescriptor object describing the method constraints of the given method. The method is uniquely identified by its name and the types of its parameters.

getConstrainedMethods() returns the MethodDescriptors of the methods matching the MethodTypes provided as parameter and having at least one constraint or cascaded parameter or return value.

getConstraintsForConstructor() returns a ConstructorDescriptor object describing the method constraints of the given constructor. The constructor is uniquely identified by its name and the types of its parameters.

getConstrainedConstructors() returns the ConstructorDescriptors of the constructors having at least one constraint or cascaded parameter or return value.

6.4. CascadableDescriptor

The CascadableDescriptor interface describes a cascadable element, i.e. an element which can be marked with @Valid in order to perform a cascaded validation of the element as described in Section 4.1.3, “Graph validation”.

package javax.validation.metadata;

/**
 * Represents a cascadable element.
 *
 * @author Gunnar Morling
 * @since 1.1
 */
public interface CascadableDescriptor {

    /**
     * Whether this element is marked for cascaded validation or not.
     *
     * @return {@code true}, if this element is marked for cascaded validation,
     *         {@code false} otherwise
     */
    boolean isCascaded();

    /**
     * Returns the group conversions configured for this element.
     *
     * @return a set containing this element's group conversions; an empty set
     *         may be returned if no conversions are configured but never
     *         {@code null}
     */
    Set<GroupConversionDescriptor> getGroupConversions();
}

The isCascaded() method returns true if the element is marked for cascaded validation.

The method getGroupConversions() returns a set with the group conversions declared for the cascadable element. An empty set will be returned if no group conversions are configured.

6.5. GroupConversionDescriptor

The GroupConversionDescriptor interface describes a group conversion rule configured for a cascadable element as described in Section 4.4.5, “Group conversion”. It is returned by CascadableDescriptor.getGroupConversions().

package javax.validation.metadata;

/**
 * A group conversion rule to be applied during cascaded validation. Two group
 * conversion descriptors are considered equal if they have the same
 * {@code from} and {@code to} group respectively.
 *
 * @author Gunnar Morling
 * @see ConvertGroup
 * @since 1.1
 */
public interface GroupConversionDescriptor {

    /**
     * Returns the source group of this conversion rule.
     *
     * @return the source group of this conversion rule
     */
    Class<?> getFrom();

    /**
     * Returns the target group of this conversion rule.
     *
     * @return the target group of this conversion rule
     */
    Class<?> getTo();
}

The getFrom() method returns the source of a group conversion rule.

The getTo() method returns the target of a group conversion rule.

6.6. PropertyDescriptor

The PropertyDescriptor interface describes a constrained property of a Java Bean.

This interface is returned by BeanDescriptor.getConstraintsForProperty(String) or BeanDescriptor.getConstrainedProperties(). Constraints declared on the attribute and the getter of the same name according to the JavaBeans rules are returned by this descriptor.

package javax.validation.metadata;

/**
 * Describes a Java Bean property hosting validation constraints.
 *
 * Constraints placed on the attribute and the getter of a given property
 * are all referenced.
 *
 * @author Emmanuel Bernard
 */
public interface PropertyDescriptor extends ElementDescriptor, CascadableDescriptor {

    /**
     * Name of the property according to the Java Bean specification.
     *
     * @return property name
     */
    String getPropertyName();
}

getPropertyName() returns the property name as described in Section 5.2, “ConstraintViolation”.

6.7. ExecutableDescriptor, MethodDescriptor and ConstructorDescriptor

The ExecutableDescriptor interface describes a constrained method or constructor of a Java type.

package javax.validation.metadata;

/**
 * Provides the common functionality of {@link MethodDescriptor} and
 * {@link ConstructorDescriptor}.
 *
 * @author Gunnar Morling
 *
 * @since 1.1
 */
public interface ExecutableDescriptor extends ElementDescriptor {

    /**
     * Returns the method name in case this descriptor represents a method or
     * the non-qualified name of the declaring class in case this descriptor
     * represents a constructor.
     *
     * @return the name of the executable represented by this descriptor
     */
    String getName();

    /**
     * Returns a list of descriptors representing this executable's
     * parameters, in the order of their declaration, including synthetic
     * parameters.
     *
     * @return a list of descriptors representing this executable's
     *         parameters; an empty list will be returned if this executable has
     *         no parameters, but never {@code null}
     */
    List<ParameterDescriptor> getParameterDescriptors();

    /**
     * Returns a descriptor containing the cross-parameter constraints
     * of this executable.
     *
     * @return a descriptor containing the cross-parameter constraints of
     *         this executable
     */
    CrossParameterDescriptor getCrossParameterDescriptor();

    /**
     * Returns a descriptor for this executable's return value.
     * <p/>
     * An executable without return value will return a descriptor
     * representing {@code void}. This descriptor will have no constraint
     * associated.
     *
     * @return a descriptor for this executable's return value
     */
    ReturnValueDescriptor getReturnValueDescriptor();

    /**
     * Returns {@code true} if the executable parameters are constrained either:
     * <ul>
     *     <li>because of a constraint on at least one of the parameters</li>
     *     <li>because of a cascade on at least one of the parameters (via
     *     {@link Valid})</li>
     *     <li>because of at least one cross-parameter constraint</li>
     * </ul>
     * <p/>
     * Also returns {@code false} if there is no parameter.
     *
     * @return {@code true} if the executable parameters are constrained
     */
    boolean hasConstrainedParameters();

    /**
     * Returns {@code true} if the executable return value is constrained
     * either:
     * <ul>
     *     <li>because of a constraint on the return value</li>
     *     <li>because validation is cascaded on the return value (via
     *     {@link Valid})</li>
     * </ul>
     * <p/>
     * Also returns {@code false} if there is no return value.
     *
     * @return {@code true} if the executable return value is constrained
     */
    boolean hasConstrainedReturnValue();

    /**
     * Returns {@code false}.
     * <p/>
     * An executable per se does not host constraints, use
     * {@link #getParameterDescriptors()}, {@link #getCrossParameterDescriptor()}
     * and {@link #getReturnValueDescriptor()} to discover constraints.
     *
     * @return {@code false}
     */
    @Override
    boolean hasConstraints();

    /**
     * Returns an empty {@code Set}.
     * <p/>
     * An executable per se does not host constraints, use
     * {@link #getParameterDescriptors()}, {@link #getCrossParameterDescriptor()}
     * and {@link #getReturnValueDescriptor()} to discover constraints.
     *
     * @return an empty {@code Set}
     */
    @Override
    Set<ConstraintDescriptor<?>> getConstraintDescriptors();

    /**
     * Returns a finder that will always return an empty {@code Set}.
     * <p/>
     * An executable per se does not host constraints, use
     * {@link #getParameterDescriptors()}, {@link #getCrossParameterDescriptor()}
     * and {@link #getReturnValueDescriptor()} to discover constraints.
     *
     * @return {@code ConstraintFinder} object
     */
    @Override
    ConstraintFinder findConstraints();
}

getName() returns the name of the represented method (e.g. "placeOrder") respectively the non-qualified name of the declaring class of the represented constructor (e.g. "OrderService").

getParameterDescriptors() returns a list of ParameterDescriptors representing the method's or constructor's parameters in order of their declaration, including synthetic parameters. An empty list will be returned in case the method or constructor has no parameters.

getCrossParameterDescriptor() returns a descriptor containing cross-parameter constraints of the method or constructor. If no cross-parameter constraint is present, the descriptor will return an empty set of constraint descriptors.

getReturnValueDescriptor() returns a descriptor for the method's or constructor's return value. A descriptor representing the special class void, without any constraint descriptors, will be returned for executables which have no return value.

hasConstrainedParameters() returns true if any of the parameters is constrained or cascaded or if the represented executable has at least one cross-parameter constraint. Returns false if there is no parameter.

hasConstrainedReturnValue() returns true if the return value is constrained or cascaded. Returns false if there is no return value.

The methods hasConstraints(), getConstraintDescriptors() and findConstraints() defined on ElementDescriptor are redefined to clarify that executables do not host constraints directly and thus will always return false or an empty set of constraints, respectively. Constraint descriptors for individual parameters can be obtained from the corresponding ParameterDescriptor object, constraint descriptors for cross-parameter constraints can be obtained from the corresponding CrossParameterDescriptor object and constraint descriptors for the return value can be obtained from ReturnValueDescriptor.

The interfaces MethodDescriptor and ConstructorDescriptor are derived from ExecutableDescriptor and allow to distinguish between descriptors representing methods and descriptors representing constructors.

package javax.validation.metadata;

/**
 * Describes a validated method.
 *
 * @author Gunnar Morling
 * @author Emmanuel Bernard
 * @since 1.1
 */
public interface MethodDescriptor extends ExecutableDescriptor {
}
package javax.validation.metadata;

/**
 * Describes a validated constructor.
 *
 * @author Gunnar Morling
 * @author Emmanuel Bernard
 * @since 1.1
 */
public interface ConstructorDescriptor extends ExecutableDescriptor {
}

MethodDescriptor objects are returned by BeanDescriptor.getConstraintsForMethod(String, Class<?>...) and BeanDescriptor.getConstrainedMethods(MethodType, MethodType...), while ConstructorDescriptor objects are returned by BeanDescriptor.getConstraintsForConstructor(Class<?>...) and BeanDescriptor.getConstrainedConstructors().

None of the metadata API methods honor the XML configuration around executable validation nor the presence of @ValidateOnExecution. In other words, all constrained methods and constructors will be returned by the metadata API regardless of these settings.

6.8. ParameterDescriptor

The ParameterDescriptor interface describes a constrained parameter of a method or constructor.

This interface is returned by MethodDescriptor.getParameterDescriptors() and ConstructorDescriptor.getParameterDescriptors().

package javax.validation.metadata;

/**
 * Describes a validated method or constructor parameter.
 *
 * @author Gunnar Morling
 * @since 1.1
 */
public interface ParameterDescriptor extends ElementDescriptor, CascadableDescriptor {

    /**
     * Returns this parameter's index within the parameter array of the method
     * or constructor holding it.
     *
     * @return this parameter's index
     */
    int getIndex();

    /**
     * Returns this parameter's name as retrieved by the current parameter name
     * resolver.
     *
     * @return this parameter's name
     */
    String getName();
}

getIndex() returns the index of the represented parameter within the parameter array of the method or constructor holding it.

getName() returns the name of the represented parameter.

6.9. CrossParameterDescriptor

The CrossParameterDescriptor interface describes a element containing all cross-parameter constraints of a method or constructor.

This interface is returned by MethodDescriptor.getCrossParameterDescriptor() and ConstructorDescriptor.getCrossParameterDescriptor().

package javax.validation.metadata;

/**
 * Describes an element holding cross-parameter constraints of a method or constructor
 *
 * @author Emmanuel Bernard
 * @since 1.1
 */
public interface CrossParameterDescriptor extends ElementDescriptor {

    /**
     * @return {@code Object[].class} - the type of the parameter array
     */
    @Override
    Class<?> getElementClass();
}

getElementClass() returns Object[].

6.10. ReturnValueDescriptor

The ReturnValueDescriptor interface describes the return value of a method or constructor.

This interface is returned by MethodDescriptor.getReturnValueDescriptor() and ConstructorDescriptor.getReturnValueDescriptor().

package javax.validation.metadata;

/**
 * Describes a validated return value of a method or constructor.
 *
 * @author Gunnar Morling
 * @since 1.1
 */
public interface ReturnValueDescriptor extends ElementDescriptor, CascadableDescriptor {
}

6.11. ConstraintDescriptor

A ConstraintDescriptor object describes a given constraint declaration (i.e. a constraint annotation).

package javax.validation.metadata;

/**
 * Describes a single constraint and its composing constraints.
 * <p/>
 * {@code T} is the constraint's annotation type.
 *
 * @author Emmanuel Bernard
 * @author Hardy Ferentschik
 */
public interface ConstraintDescriptor<T extends Annotation> {

    /**
     * Returns the annotation describing the constraint declaration.
     * If a composing constraint, attribute values are reflecting
     * the overridden attributes of the composing constraint
     *
     * @return the annotation for this constraint
     */
    T getAnnotation();

    /**
     * The non-interpolated error message
     *
     * @return the non-interpolated error message
     *
     * @since 1.1
     */
    String getMessageTemplate();

    /**
     * The set of groups the constraint is applied on.
     * If the constraint declares no group, a set with only the {@link Default}
     * group is returned.
     *
     * @return the groups the constraint is applied on
     */
    Set<Class<?>> getGroups();

    /**
     * The set of payload the constraint hosts.
     *
     * @return payload classes hosted on the constraint or an empty set if none
     */
    Set<Class<? extends Payload>> getPayload();

    /**
     * The {@link ConstraintTarget} value of {@code validationAppliesTo} if the constraint
     * hosts it or {@code null} otherwise.
     *
     * @return the {@code ConstraintTarget} value or {@code null}
     *
     * @since 1.1
     */
    ConstraintTarget getValidationAppliesTo();

    /**
     * List of the constraint validation implementation classes.
     *
     * @return list of the constraint validation implementation classes
     */
    List<Class<? extends ConstraintValidator<T, ?>>> getConstraintValidatorClasses();

    /**
     * Returns a map containing the annotation attribute names as keys and the
     * annotation attribute values as value.
     * <p/>
     * If this constraint is used as part of a composed constraint, attribute
     * values are reflecting the overridden attribute of the composing constraint.
     *
     * @return a map containing the annotation attribute names as keys
     *         and the annotation attribute values as value
     */
    Map<String, Object> getAttributes();

    /**
     * Return a set of composing {@link ConstraintDescriptor}s where each
     * descriptor describes a composing constraint. {@code ConstraintDescriptor}
     * instances of composing constraints reflect overridden attribute values in
     * {@link #getAttributes()}  and {@link #getAnnotation()}.
     *
     * @return a set of {@code ConstraintDescriptor} objects or an empty set
     *         in case there are no composing constraints
     */
    Set<ConstraintDescriptor<?>> getComposingConstraints();

    /**
     * @return {@code true} if the constraint is annotated with {@link ReportAsSingleViolation}
     */
    boolean isReportAsSingleViolation();
}

getAnnotation() returns the annotation instance (or an annotation instance representing the given constraint declaration). If ConstraintDescriptor represents a composing annotation (see Section 3.3, “Constraint composition”), the returned annotation must reflect parameter overriding. In other words, the annotation parameter values are the overridden values.

getAttributes() returns a map containing the annotation attribute names as a key, and the annotation attribute values as a value (this API is anticipated to be simpler to use by tools than reflection over the annotation instance). If ConstraintDescriptor() represents a composing annotation (see Section 3.3, “Constraint composition”), the returned Map must reflect attribute overriding.

getMessageTemplate() returns the non-interpolated error message.

getGroups() returns the groups the constraint is supposed to be applied upon. If no group is set on the constraint declaration, the Default group is returned. The groups of a composing constraint are the groups of the composed constraint.

getPayload() returns the payloads associated to the constraint or an empty set if none. The payload from the main constraint annotation is inherited by the composing annotations. Any payload definition on a composing annotation is ignored.

getValidationAppliesTo() returns the ConstraintTarget returned by validationAppliesTo if the constraint hosts the attribute or null otherwise. The constraint target from the main constraint annotation is inherited by the composing annotation. Any constraint target definition on a composing annotation is ignored.

isReportAsSingleViolation() returns true if the constraint is annotated with @ReportAsSingleViolation.

getComposingConstraints() return a set of composing ConstraintDescriptors where each descriptor describes a composing constraint.

getConstraintValidatorClasses() returns the ConstraintValidator classes associated with the constraint.

6.12. Example

Assuming the following constraint definitions

package com.acme.constraint;

@Documented
@NotNull
@Size(min=1)
@ReportAsSingleViolation
@Constraint(validatedBy = NotEmpty.NotEmptyValidator.class)
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
public @interface NotEmpty {
    String message() default "{com.acme.constraint.NotEmpty.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default { };

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        NotEmpty[] value();
    }

    class NotEmptyValidator implements ConstraintValidator<NotEmpty, String> {
        @Override
        public void initialize(NotEmpty constraintAnnotation) {}

        @Override
        public boolean isValid(String value, ConstraintValidatorContext context) {
            return true;
        }
    }
}

@Documented
@Constraint(validatedBy = ValidInterval.Validator.class)
@Target({ METHOD, ANNOTATION_TYPE, CONSTRUCTOR })
@Retention(RUNTIME)
public @interface ValidInterval {
    String message() default "{com.acme.constraint.ValidInterval.message}";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default { };
    int startParameter();
    int endParameter();

    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {
        ValidInterval[] value();
    }

    @SupportedValidationTarget(PARAMETERS)
    class Validator implements ConstraintValidator<ValidInterval, Object[]> {
        
        private int start;
        private int end;

        @Override
        public void initialize(ValidInterval constraintAnnotation) {
            this.start = constraintAnnotation.startParameter();
            this.end = constraintAnnotation.endParameter();
        }

        @Override
        public boolean isValid(Object[] value, ConstraintValidatorContext context) {
            return Integer.parseInt( String.valueOf( value[start] ) ) < 
                   Integer.parseInt( String.valueOf( value[end] ) );
        }
    }
}

and the following class definitions

public class Author {
    private String firstName;
    
    @NotEmpty(message="lastname must not be null")
    private String lastName;

    @Size(max=30)
    private String company;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public String getCompany() {
        return company;
    }

    public void setCompany(String company) {
        this.company = company;
    }
}

public class Book {

    public interface FirstLevelCheck {}
    public interface SecondLevelCheck {}
    
    private String title;
    private String description;

    @Valid
    @NotNull
    private Author author;

    @Valid
    public Book(
            String title, 
            @Size(max=30) String description, 
            @Valid
            @ConvertGroup(from=Default.class, to=SecondLevelCheck.class)
            Author author) {
        [...]
    }
    
    public Book() {
        [...]
    }
     
    @NotEmpty(groups={FirstLevelCheck.class, Default.class})
    @Size(max=30)
    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Author getAuthor() {
        return author;
    }

    public void setAuthor(Author author) {
        this.author = author;
    }

    public String getDescription() {
        return description;
    }

    public void setAuthor(String description) {
        this.description = description;
    }
    
    @ValidInterval(startParameter=1, endParameter=2)
    public void addChapter(String title, int startPage, int endPage) {
        [...]
    }
}

The following assertions are true.

BeanDescriptor bookDescriptor = validator.getConstraintsForClass(Book.class);

assert ! bookDescriptor.hasConstraints();

assert bookDescriptor.isBeanConstrained();
assert bookDescriptor.getConstrainedMethods( MethodType.NON_GETTER ).size() > 0;


assert bookDescriptor.getConstraintDescriptors().size() == 0; //no bean-level constraint

//more specifically "author" and "title"
assert bookDescriptor.getConstrainedProperties().size() == 2;

//not a property
assert bookDescriptor.getConstraintsForProperty("doesNotExist") == null; 

//property with no constraint
assert bookDescriptor.getConstraintsForProperty("description") == null; 

PropertyDescriptor propertyDescriptor = bookDescriptor.getConstraintsForProperty("title");
assert propertyDescriptor.getConstraintDescriptors().size() == 2;
assert "title".equals( propertyDescriptor.getPropertyName() );

//assuming the implementation returns the @NotEmpty constraint first
ConstraintDescriptor<?> constraintDescriptor = propertyDescriptor.getConstraintDescriptors()
                                                              .iterator().next();
assert constraintDescriptor.getAnnotation().annotationType().equals( NotEmpty.class );
assert constraintDescriptor.getGroups().size() == 2; //FirstLevelCheck and Default
assert constraintDescriptor.getComposingConstraints().size() == 2;
assert constraintDescriptor.isReportAsSingleViolation() == true;

//@NotEmpty cannot be null
boolean notNullPresence = false;
for ( ConstraintDescriptor<?> composingDescriptor : constraintDescriptor.getComposingConstraints() ) {
    if ( composingDescriptor.getAnnotation().annotationType().equals( NotNull.class ) ) {
        notNullPresence = true;
    }
}
assert notNullPresence; 

//assuming the implementation returns the Size constraint second
constraintDescriptor = propertyDescriptor.getConstraintDescriptors().iterator().next();
assert constraintDescriptor.getAnnotation().annotationType().equals( Size.class );
assert constraintDescriptor.getAttributes().get("max") == Integer.valueOf( 30 );
assert constraintDescriptor.getGroups().size() == 1;

propertyDescriptor = bookDescriptor.getConstraintsForProperty("author");
assert propertyDescriptor.getConstraintDescriptors().size() == 1;
assert propertyDescriptor.isCascaded();

//getTitle() and addChapter()
assert bookDescriptor.getConstrainedMethods( MethodType.GETTER, MethodType.NON_GETTER ).size() == 2;

//the constructor accepting title, description and author
assert bookDescriptor.getConstrainedConstructors().size() == 1;

ConstructorDescriptor constructorDescriptor = bookDescriptor.getConstraintsForConstructor(
    String.class, String.class, Author.class 
);
assert constructorDescriptor.getName().equals( "Book" );
assert constructorDescriptor.getElementClass() == Book.class;
assert constructorDescriptor.hasConstrainedParameters() == true;

//return value is marked for cascaded validation
assert constructorDescriptor.hasConstrainedReturnValue() == true;

//constraints are retrieved via the sub-descriptors for parameters etc.
assert constructorDescriptor.hasConstraints() == false;

//one descriptor for each parameter
assert constructorDescriptor.getParameterDescriptors().size() == 3;

//"description" parameter
ParameterDescriptor parameterDescriptor = constructorDescriptor.getParameterDescriptors().get( 1 );

//Assuming the default parameter name provider
assert parameterDescriptor.getName().equals( "arg1" );
assert parameterDescriptor.getElementClass() == String.class;
assert parameterDescriptor.getIndex() == 1;
assert parameterDescriptor.hasConstraints() == true;

Set<ConstraintDescriptor<?>> parameterConstraints = parameterDescriptor.getConstraintDescriptors();
assert parameterConstraints.iterator().next().getAnnotation().annotationType() == Size.class;

//"author" parameter
parameterDescriptor = constructorDescriptor.getParameterDescriptors().get( 2 );
assert parameterDescriptor.hasConstraints() == false;
assert parameterDescriptor.isCascaded() == true;

//group conversion on "author" parameter
GroupConversionDescriptor groupConversion =
    parameterDescriptor.getGroupConversions().iterator().next();
assert groupConversion.getFrom() == Default.class;
assert groupConversion.getTo() == SecondLevelCheck.class;

//constructor return value
ReturnValueDescriptor returnValueDescriptor = constructorDescriptor.getReturnValueDescriptor();
assert returnValueDescriptor.hasConstraints() == false;
assert returnValueDescriptor.isCascaded() == true;

//a getter is also a method which is constrained on its return value
MethodDescriptor methodDescriptor = bookDescriptor.getConstraintsForMethod( "getTitle" );
assert methodDescriptor.getName().equals( "getTitle" );
assert methodDescriptor.getElementClass() == String.class;
assert methodDescriptor.hasConstrainedParameters() == false;
assert methodDescriptor.hasConstrainedReturnValue() == true;
assert methodDescriptor.hasConstraints() == false;

returnValueDescriptor = methodDescriptor.getReturnValueDescriptor();
assert returnValueDescriptor.getElementClass() == String.class;
assert returnValueDescriptor.getConstraintDescriptors().size() == 2;
assert returnValueDescriptor.isCascaded() == false;

//void method which has a cross-parameter constraint
methodDescriptor = bookDescriptor.getConstraintsForMethod(
    "addChapter", String.class, int.class, int.class
);
assert methodDescriptor.getElementClass() == void.class;
assert methodDescriptor.hasConstrainedParameters() == true;
assert methodDescriptor.hasConstrainedReturnValue() == false;

//cross-parameter constraints accessible via separate descriptor
assert methodDescriptor.hasConstraints() == false;

assert methodDescriptor.getReturnValueDescriptor().getElementClass() == void.class;

//cross-parameter descriptor
CrossParameterDescriptor crossParameterDescriptor = methodDescriptor.getCrossParameterDescriptor();
assert crossParameterDescriptor.getElementClass() == Object[].class;
assert crossParameterDescriptor.hasConstraints() == true;

ConstraintDescriptor<?> crossParameterConstraint =
    crossParameterDescriptor.getConstraintDescriptors().iterator().next();
assert crossParameterConstraint.getAnnotation().annotationType() == ValidInterval.class;

Chapter 7. Built-in Constraint definitions

The specification defines a small set of built-in constraints. Their usage is encouraged both in regular constraint declarations and as composing constraints. Using this set of constraints will enhance portability of your constraints across constraint-consuming frameworks relying on the metadata API (such as client side validation frameworks or database schema generation frameworks).

Built-in annotations are annotated with an empty @Constraint annotation to avoid any dependency between the specification API and a specific implementation. Each Bean Validation provider must recognize built-in constraint annotations as valid constraint definitions and provide compliant constraint implementations for each. The built-in constraint validation implementation is having a lower priority than an XML mapping definition. In other words ConstraintValidator implementations for built-in constraints can be overridden by using the XML mapping (see Section 8.1.2, “Overriding constraint definitions in XML”).

All built-in constraints are in the javax.validation.constraints package. Here is the list of constraints and their declaration.

Example 7.1. @Null constraint

package javax.validation.constraints;

/**
 * The annotated element must be {@code null}.
 * Accepts any type.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface Null {

    String message() default "{javax.validation.constraints.Null.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * Defines several {@link Null} annotations on the same element.
     *
     * @see javax.validation.constraints.Null
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        Null[] value();
    }
}

Example 7.2. @NotNull constraint

package javax.validation.constraints;

/**
 * The annotated element must not be {@code null}.
 * Accepts any type.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface NotNull {

    String message() default "{javax.validation.constraints.NotNull.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * Defines several {@link NotNull} annotations on the same element.
     *
     * @see javax.validation.constraints.NotNull
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        NotNull[] value();
    }
}

Example 7.3. @AssertTrue constraint

package javax.validation.constraints;

/**
 * The annotated element must be true.
 * Supported types are {@code boolean} and {@code Boolean}.
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface AssertTrue {

    String message() default "{javax.validation.constraints.AssertTrue.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * Defines several {@link AssertTrue} annotations on the same element.
     *
     * @see AssertTrue
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        AssertTrue[] value();
    }
}

Example 7.4. @AssertFalse constraint

package javax.validation.constraints;

/**
 * The annotated element must be false.
 * Supported types are {@code boolean} and {@code Boolean}.
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface AssertFalse {

    String message() default "{javax.validation.constraints.AssertFalse.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * Defines several {@link AssertFalse} annotations on the same element.
     *
     * @see javax.validation.constraints.AssertFalse
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        AssertFalse[] value();
    }
}

Example 7.5. @Min constraint

package javax.validation.constraints;

/**
 * The annotated element must be a number whose value must be higher or
 * equal to the specified minimum.
 * <p/>
 * Supported types are:
 * <ul>
 *     <li>{@code BigDecimal}</li>
 *     <li>{@code BigInteger}</li>
 *     <li>{@code byte}, {@code short}, {@code int}, {@code long}, and their respective
 *     wrappers</li>
 * </ul>
 * Note that {@code double} and {@code float} are not supported due to rounding errors
 * (some providers might provide some approximative support).
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface Min {

    String message() default "{javax.validation.constraints.Min.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * @return value the element must be higher or equal to
     */
    long value();

    /**
     * Defines several {@link Min} annotations on the same element.
     *
     * @see Min
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        Min[] value();
    }
}

Example 7.6. @Max constraint

package javax.validation.constraints;

/**
 * The annotated element must be a number whose value must be lower or
 * equal to the specified maximum.
 * <p/>
 * Supported types are:
 * <ul>
 *     <li>{@code BigDecimal}</li>
 *     <li>{@code BigInteger}</li>
 *     <li>{@code byte}, {@code short}, {@code int}, {@code long}, and their respective
 *     wrappers</li>
 * </ul>
 * Note that {@code double} and {@code float} are not supported due to rounding errors
 * (some providers might provide some approximative support).
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface Max {

    String message() default "{javax.validation.constraints.Max.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * @return value the element must be lower or equal to
     */
    long value();

    /**
     * Defines several {@link Max} annotations on the same element.
     *
     * @see Max
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        Max[] value();
    }
}

Example 7.7. @DecimalMin constraint

package javax.validation.constraints;

/**
 * The annotated element must be a number whose value must be higher or
 * equal to the specified minimum.
 * <p/>
 * Supported types are:
 * <ul>
 *     <li>{@code BigDecimal}</li>
 *     <li>{@code BigInteger}</li>
 *     <li>{@code CharSequence}</li>
 *     <li>{@code byte}, {@code short}, {@code int}, {@code long}, and their respective
 *     wrappers</li>
 * </ul>
 * Note that {@code double} and {@code float} are not supported due to rounding errors
 * (some providers might provide some approximative support).
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface DecimalMin {

    String message() default "{javax.validation.constraints.DecimalMin.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * The {@code String} representation of the min value according to the
     * {@code BigDecimal} string representation.
     *
     * @return value the element must be higher or equal to
     */
    String value();

    /**
     * Specifies whether the specified minimum is inclusive or exclusive.
     * By default, it is inclusive.
     *
     * @return {@code true} if the value must be higher or equal to the specified minimum,
     *         {@code false} if the value must be higher
     *
     * @since 1.1
     */
    boolean inclusive() default true;

    /**
     * Defines several {@link DecimalMin} annotations on the same element.
     *
     * @see DecimalMin
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        DecimalMin[] value();
    }
}

Example 7.8. @DecimalMax constraint

package javax.validation.constraints;

/**
 * The annotated element must be a number whose value must be lower or
 * equal to the specified maximum.
 * <p/>
 * Supported types are:
 * <ul>
 *     <li>{@code BigDecimal}</li>
 *     <li>{@code BigInteger}</li>
 *     <li>{@code CharSequence}</li>
 *     <li>{@code byte}, {@code short}, {@code int}, {@code long}, and their respective
 *     wrappers</li>
 * </ul>
 * Note that {@code double} and {@code float} are not supported due to rounding errors
 * (some providers might provide some approximative support).
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface DecimalMax {

    String message() default "{javax.validation.constraints.DecimalMax.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * The {@code String} representation of the max value according to the
     * {@code BigDecimal} string representation.
     *
     * @return value the element must be lower or equal to
     */
    String value();

    /**
     * Specifies whether the specified maximum is inclusive or exclusive.
     * By default, it is inclusive.
     *
     * @return {@code true} if the value must be lower or equal to the specified maximum,
     *         {@code false} if the value must be lower
     *
     * @since 1.1
     */
    boolean inclusive() default true;

    /**
     * Defines several {@link DecimalMax} annotations on the same element.
     *
     * @see DecimalMax
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        DecimalMax[] value();
    }
}

Example 7.9. @Size constraint

package javax.validation.constraints;

/**
 * The annotated element size must be between the specified boundaries (included).
 * <p/>
 * Supported types are:
 * <ul>
 *     <li>{@code CharSequence} (length of character sequence is evaluated)</li>
 *     <li>{@code Collection} (collection size is evaluated)</li>
 *     <li>{@code Map} (map size is evaluated)</li>
 *     <li>Array (array length is evaluated)</li>
 * </ul>
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface Size {

    String message() default "{javax.validation.constraints.Size.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * @return size the element must be higher or equal to
     */
    int min() default 0;

    /**
     * @return size the element must be lower or equal to
     */
    int max() default Integer.MAX_VALUE;

    /**
     * Defines several {@link Size} annotations on the same element.
     *
     * @see Size
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        Size[] value();
    }
}

Example 7.10. @Digits constraint

package javax.validation.constraints;

/**
 * The annotated element must be a number within accepted range
 * Supported types are:
 * <ul>
 *     <li>{@code BigDecimal}</li>
 *     <li>{@code BigInteger}</li>
 *     <li>{@code CharSequence}</li>
 *     <li>{@code byte}, {@code short}, {@code int}, {@code long}, and their respective
 *     wrapper types</li>
 * </ul>
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface Digits {

    String message() default "{javax.validation.constraints.Digits.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * @return maximum number of integral digits accepted for this number
     */
    int integer();

    /**
     * @return maximum number of fractional digits accepted for this number
     */
    int fraction();

    /**
     * Defines several {@link Digits} annotations on the same element.
     *
     * @see Digits
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        Digits[] value();
    }
}

Example 7.11. @Past constraint

package javax.validation.constraints;

/**
 * The annotated element must be a date in the past.
 * Now is defined as the current time according to the virtual machine.
 * <p/>
 * The calendar used if the compared type is of type {@code Calendar}
 * is the calendar based on the current timezone and the current locale.
 * <p/>
 * Supported types are:
 * <ul>
 *     <li>{@code java.util.Date}</li>
 *     <li>{@code java.util.Calendar}</li>
 * </ul>
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface Past {

    String message() default "{javax.validation.constraints.Past.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * Defines several {@link Past} annotations on the same element.
     *
     * @see Past
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        Past[] value();
    }
}

Example 7.12. @Future constraint

package javax.validation.constraints;

/**
 * The annotated element must be a date in the future.
 * Now is defined as the current time according to the virtual machine
 * The calendar used if the compared type is of type {@code Calendar}
 * is the calendar based on the current timezone and the current locale.
 * <p/>
 * Supported types are:
 * <ul>
 *     <li>{@code java.util.Date}</li>
 *     <li>{@code java.util.Calendar}</li>
 * </ul>
 * <p/>
 * {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface Future {

    String message() default "{javax.validation.constraints.Future.message}";

    Class<?>[] groups() default { };

    Class<? extends Payload>[] payload() default { };

    /**
     * Defines several {@link Future} annotations on the same element.
     *
     * @see Future
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        Future[] value();
    }
}

Example 7.13. @Pattern constraint

package javax.validation.constraints;

/**
 * The annotated {@code CharSequence} must match the specified regular expression.
 * The regular expression follows the Java regular expression conventions
 * see {@link java.util.regex.Pattern}.
 * <p/>
 * Accepts {@code CharSequence}. {@code null} elements are considered valid.
 *
 * @author Emmanuel Bernard
 */
@Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
@Retention(RUNTIME)
@Documented
@Constraint(validatedBy = { })
public @interface Pattern {

    /**
     * @return the regular expression to match
     */
    String regexp();

    /**
     * @return array of {@code Flag}s considered when resolving the regular expression
     */
    Flag[] flags() default { };

    /**
     * @return the error message template
     */
    String message() default "{javax.validation.constraints.Pattern.message}";

    /**
     * @return the groups the constraint belongs to
     */
    Class<?>[] groups() default { };

    /**
     * @return the payload associated to the constraint
     */
    Class<? extends Payload>[] payload() default { };

    /**
     * Possible Regexp flags.
     */
    public static enum Flag {

        /**
         * Enables Unix lines mode.
         *
         * @see java.util.regex.Pattern#UNIX_LINES
         */
        UNIX_LINES( java.util.regex.Pattern.UNIX_LINES ),

        /**
         * Enables case-insensitive matching.
         *
         * @see java.util.regex.Pattern#CASE_INSENSITIVE
         */
        CASE_INSENSITIVE( java.util.regex.Pattern.CASE_INSENSITIVE ),

        /**
         * Permits whitespace and comments in pattern.
         *
         * @see java.util.regex.Pattern#COMMENTS
         */
        COMMENTS( java.util.regex.Pattern.COMMENTS ),

        /**
         * Enables multiline mode.
         *
         * @see java.util.regex.Pattern#MULTILINE
         */
        MULTILINE( java.util.regex.Pattern.MULTILINE ),

        /**
         * Enables dotall mode.
         *
         * @see java.util.regex.Pattern#DOTALL
         */
        DOTALL( java.util.regex.Pattern.DOTALL ),

        /**
         * Enables Unicode-aware case folding.
         *
         * @see java.util.regex.Pattern#UNICODE_CASE
         */
        UNICODE_CASE( java.util.regex.Pattern.UNICODE_CASE ),

        /**
         * Enables canonical equivalence.
         *
         * @see java.util.regex.Pattern#CANON_EQ
         */
        CANON_EQ( java.util.regex.Pattern.CANON_EQ );

        //JDK flag value
        private final int value;

        private Flag(int value) {
            this.value = value;
        }

        /**
         * @return flag value as defined in {@link java.util.regex.Pattern}
         */
        public int getValue() {
            return value;
        }
    }

    /**
     * Defines several {@link Pattern} annotations on the same element.
     *
     * @see Pattern
     */
    @Target({ METHOD, FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER })
    @Retention(RUNTIME)
    @Documented
    @interface List {

        Pattern[] value();
    }
}

Chapter 8. XML deployment descriptor

Two kinds of XML descriptors are used by Bean Validation. The first one describes the Bean Validation configuration provided as META-INF/validation.xml. The second one describes constraints declarations and closely matches the annotations declaration approach. If an XML descriptor does not validate against the corresponding XSD file, a ValidationException is raised.

8.1. Constraint definition and declaration

Bean Validation lets you declare constraints via XML rather than annotations. You can either ignore constraints declared via annotations or consider XML as adding additional constraints on top of annotation constraints. While it is not possible to define a new constraint via XML, you can redefine the list of ConstraintValidator classes associated to a given constraint definition.

There is no distinction between an annotation based constraint declaration and an XML based constraint declaration: they are considered equivalent and should be treated as such by the Bean Validation provider. The rest of the specification only refers to annotations as validation metadata: it should be read as annotation or their XML descriptor equivalent.

Specifically when exploring metadata, the Bean Validation provider must ensure that an annotation instance corresponding to the XML declaration is provided via ConstraintDescriptor.getAnnnotation(). The annotation elements as well as ConstraintValidator.getAttributes() must reflect the values described in the XML declaration (see Section 8.1.3, “Converting the string representation of a value”). Likewise, ConstraintDescriptor.getConstraintValidatorClasses() must reflect XML based constraint definition overriding (see Section 8.1.2, “Overriding constraint definitions in XML”).

A given class must not be described more than once amongst all the XML mapping descriptors. A given field or getter must not be described more than once on a given class description. A given constraint definition must not be overridden more than once amongst all the XML mapping descriptors. If any of these rule is violated in a given validation deployment, a ValidationException is raised during the creation of the ValidatorFactory.

The schema is provided in Section 8.1.4, “XML Schema”.

8.1.1. Constraint declaration in XML

If default-package is set, all unqualified class names (including annotations) are considered part of the package described by default-package.

A given JavaBean is described by the bean element. The name of the class is mandatory. By default, all constraint declarations expressed via annotation are ignored for classes described in XML. You can force Bean Validation to consider both annotations and XML constraint declarations by using ignore-annotations="false" on bean.

Note

The ignore-annotations setting is not inherited from nor by the class hierarchy. In other words, it only applies to the current bean only.

If the name of the class does refer to a class not present in the classpath, a ValidationException is raised.

Example 8.1. Example of bean XML declaration

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">

    <default-package>com.acme.app.domain</default-package>

    <bean class="Customer" ignore-annotations="false">
        [...]
    </bean>
    <bean class="com.acme.common.model.Address">
        [...]
    </bean>
</constraint-mappings>

8.1.1.1. Class-level overriding

Class level annotations are described via the class element. If ignore-annotations is declared, Bean Validation must honor the explicit value for this element. If not declared, the default value defined in the encapsulating bean element is considered.

When ignore-annotations is true, class-level Bean Validation annotations are ignored for this class (including the @GroupSequence). When ignore-annotations is false:

  • Constraints declared in XML and constraints declared in annotations are added and form the list of class-level declared constraints.

  • @GroupSequence is considered unless group-sequence element is explicitly used.

Example 8.2. Example of class-level declaration

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">
    <default-package>com.acme.app.domain</default-package>
    <bean class="Customer" ignore-annotations="false">
        <class ignore-annotations="true">
            [...]
        </class>
    </bean>
    <bean class="com.acme.common.model.Address">
        <class>
            [...]
        </class>
    </bean>
</constraint-mappings>

8.1.1.2. Field-level overriding

Field level annotations are described via the field element. The name attribute corresponds to the name of the field considered. If ignore-annotations is declared, Bean Validation must honor the explicit value for this element. If not declared, the default value defined in the encapsulating bean element is considered.

When ignore-annotations is true, field-level Bean Validation annotations on the targeted field are ignored (including @Valid and @ConvertGroup). When ignore-annotations is false:

  • Constraints declared in XML and constraints declared in annotations are added and form the list of field-level declared constraints.

  • @Valid is considered unless the valid element is explicitly used. Note that the only way to disable cascading on a field marked as @Valid is to use ignore-annotations=true.

  • Group conversions declared in XML and via the @ConvertGroup annotation are added and form the list of applied conversions. Note that the rules for the declaration of group conversions as outlined in Section 4.4.5, “Group conversion” apply, in particular it is not legal to declare several conversions for the same source group.

If the name of the field does not correspond to a field in the given bean a ValidationException is raised.

Example 8.3. Field-level declaration

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">
    <default-package>com.acme.app.domain</default-package>
    <bean class="Customer" ignore-annotations="false">
        <field name="firstName">
            [...]
        </field>
        <field name="orders">
            <valid/>
            [...]
        </field>
    </bean>
</constraint-mappings>

8.1.1.3. Property-level overriding

Property-level annotations are described via the getter element. The name attribute corresponds to the name of the property considered as defined in Section 4.1.2, “Field and property validation” (for example a getter String getAge() would have <getter name="age"/> as a corresponding descriptor). If ignore-annotations is declared, Bean Validation must honor the explicit value for this element. If not declared, the default value defined in the encapsulating bean element is considered.

When ignore-annotations is true, property-level Bean Validation annotations on the targeted property are ignored (including @Valid and @ConvertGroup). When ignore-annotations is false:

  • Constraints declared in XML and constraints declared in annotations are added and form the list of property-level declared constraints.

  • @Valid is considered unless the valid element is explicitly used. Note that the only way to disable cascading on a property marked as @Valid is to use ignore-annotations=true.

  • Group conversions declared in XML and via the @ConvertGroup annotation are added and form the list of applied conversions. Note that the rules for the declaration of group conversions as outlined in Section 4.4.5, “Group conversion” apply, in particular it is not legal to declare several conversions for the same source group.

If the name of the property does not correspond to a property in the given bean a ValidationException is raised.

Example 8.4. Property-level declaration

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">
    <default-package>com.acme.app.domain</default-package>
    <bean class="Customer" ignore-annotations="false">
        <getter name="firstName">
            [...]
        </getter>
        <getter name="orders">
            <valid/>
            [...]
        </getter>
    </bean>
</constraint-mappings>

8.1.1.4. Constructor-level overriding

Constructor-level annotations are described via the constructor element.

To identify a constructor to be configured, zero or more parameter elements are used, matching the number and types of parameters of the configured constructor. When configuring the default constructor, no parameter element is to be used. The parameter types are specified using their fully qualified name using the syntax described in the documentation of java.lang.Class.getName().

Let's look at some examples:

  • "java.lang.String" must be specified for a parameter of type java.lang.String

  • "long" must be specified for a parameter of type long

  • "[Ljava.lang.Object;" must be specified for a parameter of type java.lang.Object[]

Varargs parameters are specified using the corresponding array type, e.g. a parameter String... must be specified as "[Ljava.lang.String;".

If the default-package element is configured for the mapping file, any unqualified class names will be resolved using the given default package.

Note

You must declare all parameters even if they are not reconfigured to ensure the right constructor is identified.

If no constructor with the specified parameter types exists in the given bean a ValidationException is raised.

The optional return-value element is used to change the configuration of a constructor's return value if required.

The optional cross-parameter element is used to change the configuration of a constructor's cross-parameter constraints if required.

The constraints applying for a constructor's parameters and its return value are specified by adding constraint elements to the parameter and return-value elements respectively. Whether or not to perform cascaded validation is controlled using the valid element. Group conversion rules for cascaded validation are specified using the convert-group element.

The cross-parameter constraints applied on a constructor parameter list are specified by adding constraint elements to the cross-parameter element.

If ignore-annotations is declared on the parameter, cross-parameter element or return value level, Bean Validation must honor the explicit value for this element. Otherwise, if ignore-annotations is declared for the constructor element, Bean Validation must honor this value. Otherwise, the default value declared in the encapsulating bean element is considered.

When ignore-annotations is true, Bean Validation annotations on the targeted constructor or parameter are ignored (including @Valid and @ConvertGroup). When ignore-annotations is false:

  • Constraints declared in XML and constraints declared in annotations are added and form the list of declared parameter, cross-parameter or return value constraints respectively.

  • @Valid is considered unless the valid element is explicitly used. Note that the only way to disable cascading on a constructor parameter or return value marked as @Valid is to use ignore-annotations=true. This does not apply to cross-parameter elements as cascading does not make sense in this situation.

  • Group conversions declared in XML and via the @ConvertGroup annotation are added and form the list of applied conversions. Note that the rules for the declaration of group conversions as outlined in Section 4.4.5, “Group conversion” apply, in particular it is not legal to declare several conversions for the same source group. This does not apply to cross-parameter elements as cascading does not make sense in this situation.

Example 8.5. Constructor-level declaration

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">
    <default-package>com.acme.app.domain</default-package>
    <bean class="Customer" ignore-annotations="false">
        <constructor ignore-annotations="true">
            <parameter type="java.lang.String">
                [...]
            </parameter>
            <parameter type="int">
                <valid/>
                [...]
            </parameter>
            <parameter type="long" ignore-annotations="false"/>
            <cross-parameter ignore-annotations="false">
                [...]
            </cross-parameter>
            <return-value>
                <valid/>
                [...]
            </return-value>
            [...]
        </constructor>

    </bean>
</constraint-mappings>

8.1.1.5. Method-level overriding

Method-level annotations are described via the method element.

To identify a method to be configured, zero or more parameter elements are used, matching the number and types of parameters of the configured method. The parameter types are specified using their fully qualified name using the syntax described in the documentation of java.lang.Class.getName().

Let's look at some examples:

  • "java.lang.String" must be specified for a parameter of type java.lang.String

  • "long" must be specified for a parameter of type long

  • "[Ljava.lang.Object;" must be specified for a parameter of type java.lang.Object[]

Varargs parameters are specified using the corresponding array type, e.g. a parameter String... must be specified as "[Ljava.lang.String;".

If the default-package element is configured for the mapping file, any unqualified class names will be resolved using the given default package.

Note

You must declare all parameters even if they are not reconfigured to ensure the right method is identified.

Note

A given getter method representing a JavaBeans property may either be configured using the getter or the method element, but not both. If a getter element and a method element referring to the same method are detected by the Bean Validation provider, a ValidationException is raised.

If no method with the specified name and parameter types exists in the given bean a ValidationException is raised.

The optional return-value element is used to change the configuration of a method's return value if required.

The optional cross-parameter element is used to change the configuration of a method's cross-parameter constraints if required.

The constraints applying for a method's parameters and its return value are specified by adding constraint elements to the parameter and return-value elements respectively. Whether or not to perform cascaded validation is controlled using the valid element. Group conversion rules for cascaded validation are specified using the convert-group element.

The cross-parameter constraints applied on a method parameter list are specified by adding constraint elements to the cross-parameter element.

If ignore-annotations is declared on the parameter, cross-parameter element or return value level, Bean Validation must honor the explicit value for this element. Otherwise, if ignore-annotations is declared for the method element, Bean Validation must honor this value. Otherwise, the default value declared in the encapsulating bean element is considered.

When ignore-annotations is true, Bean Validation annotations on the targeted method or parameter are ignored (including @Valid and @ConvertGroup). When ignore-annotations is false:

  • Constraints declared in XML and constraints declared in annotations are added and form the list of declared parameter, cross-parameter or return value constraints respectively.

  • @Valid is considered unless the valid element is explicitly used. Note that the only way to disable cascading on a method parameter or return value marked as @Valid is to use ignore-annotations=true. This does not apply to cross-parameter elements as cascading does not make sense in this situation.

  • Group conversions declared in XML and via the @ConvertGroup annotation are added and form the list of applied conversions. Note that the rules for the declaration of group conversions as outlined in Section 4.4.5, “Group conversion” apply, in particular it is not legal to declare several conversions for the same source group. This does not apply to cross-parameter elements as cascading does not make sense in this situation.

Example 8.6. Method-level declaration

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">
    <default-package>com.acme.app.domain</default-package>
    <bean class="Customer" ignore-annotations="false">
        <method name="update" ignore-annotations="true">
            <parameter type="java.lang.String">
                [...]
            </parameter>
            <parameter type="int">
                <valid/>
                [...]
            </parameter>
            <parameter type="long" ignore-annotations="false"/>
            <cross-parameter ignore-annotations="false">
                [...]
            </cross-parameter>
            <return-value>
                <valid/>
                [...]
            </return-value>
            [...]
        </method>

    </bean>
</constraint-mappings>

8.1.1.6. Constraint declaration

New constraint declarations are represented by the constraint element. The annotation attribute is the class name of the annotation representing the constraint. Message, groups and payload are defined respectively by the message, groups and payload elements.

Other custom elements of an annotation are represented by element. The name attribute is mandatory and represents the name of the element in the constraint declaration. message”, “groups” and “payload” are not permitted names, use the message, groups or payload elements instead. Otherwise a ValidationException is raised.

Note

validationAppliesTo (see Section 3.1.1.4, “validationAppliesTo”) is not necessary as cross-parameter constraints and return value constraints are declared in different XML elements, respectively cross-parameter and return-value.

If the element represents a primitive type, a class or an enum, the string representation of its value is placed in the element itself. See Section 8.1.3, “Converting the string representation of a value” for a detailed explanation of the conversion rules from string to the type.

If the element represents a primitive type array, a class array or an enum array, the string representation of each value is placed in a value element placed under the element itself.

If the element represents an annotation, the annotation element is used to represent the annotation and placed under element. An annotation element contains element elements.

If the element represents an array of annotations, one or more annotation elements are placed under element.

Elements with default values in the annotation definition do not have to be represented in XML: the default value will be used in this case. If an XML constraint declaration is missing mandatory elements, or if it contains elements not part of the constraint definition, a ValidationException is raised.

Example 8.7. Constraint declaration

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">
    <default-package>com.acme.app.domain</default-package>
    <bean class="Customer" ignore-annotations="false">

        <field name="firstName">


            <!-- @LooksLike(patterns={
                      @Pattern(value="myRegExp", flag=PatternFlag.INSENSITIVE),
                      @Pattern(value="my2ndRegExp")}
                  )
             -->
            <constraint annotation="com.acme.app.constraint.LooksLike">
                <element name="patterns">
                    <annotation>
                        <element name="value">myRegExp</element>
                        <element name="flag">
                            <value>INSENSITIVE</value>
                        </element>
                    </annotation>
                    <annotation>
                        <element name="value">my2ndRegExp</element>
                    </annotation>
                </element>
            </constraint>


        </field>
        <field name="orders">
            <valid/>


            <!-- @DiscreteSize(value={ 0, 20 } )
             -->
            <constraint annotation="com.acme.app.constraint.DiscreteSize">
                <element name="value">
                    <value>0</value>
                    <value>20</value>
                </element>
            </constraint>


        </field>

        <getter name="orders">
            <valid/>


            <!-- @Size(message="Size is limited",
                       groups={Default.class, LightValidation.class},
                       max=30
                 )
            -->
            <constraint annotation="javax.validation.constraints.Size">
                <message>Size is limited</message>
                <groups>
                    <value>com.acme.app.model.LightValidation</value>
                    <value>javax.persistence.Default</value>
                </groups>
                <payload>
                    <value>com.acme.app.model.WARN</value>
                </payload>
                <element name="max">30</element>
            </constraint>


        </getter>

        <constructor ignore-annotations="true">
            <parameter type="java.lang.String">

                <!-- @DiscreteSize(value={ 0, 20 } ) -->
                <constraint annotation="com.acme.app.constraint.DiscreteSize">
                    <element name="value">
                        <value>0</value>
                        <value>20</value>
                    </element>
                </constraint>
            </parameter>
        </constructor>

        <method name="update" ignore-annotations="true">
            <parameter type="java.lang.String">

                <!-- @DiscreteSize(value={ 0, 20 } ) -->
                <constraint annotation="com.acme.app.constraint.DiscreteSize">
                    <element name="value">
                        <value>0</value>
                        <value>20</value>
                    </element>
                </constraint>
            </parameter>

            <return-value>

                <!-- @ValidCustomer -->
                <constraint annotation="com.acme.app.constraint.ValidCustomer"/>
            </return-value>
        </method>

        <method name="resetPassword" ignore-annotations="false">
            <parameter type="java.lang.String"/>
            <parameter type="java.lang.String"/>

            <cross-parameter>
                <!-- @ValidResetPasswordParameters -->
                <constraint annotation="com.acme.app.constraint.ValidResetPasswordParameters"/>
            </cross-parameter>
        </method>
    </bean>
</constraint-mappings>

8.1.1.7. Declaration of group conversions

Group conversion rules are declared by specifying one or more convert-group elements within the field, getter, parameter and return-value elements.

Source and target group of a conversion rule are given by specifying their fully-qualified names within the from and to attribute respectively. If the default-package element is configured for the mapping file, any unqualified class names will be resolved using the given default package.

Example 8.8. Declaration of group conversions

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">
    <default-package>com.acme.app.domain</default-package>
    <bean class="Customer" ignore-annotations="false">

        <field name="firstName">
            <valid/>
            <convert-group from="javax.validation.groups.Default" to="com.acme.CustomerBasic"/>
            <convert-group from="com.acmenote.Advanced" to="com.acme.CustomerComplex"/>
        </field>

        <getter name="orders">
            <valid/>
            <convert-group from="javax.validation.groups.Default" to="com.acme.CustomerBasic"/>
        </getter>

        <constructor>
            <parameter type="java.lang.String">
                <valid/>
                <convert-group from="javax.validation.groups.Default" to="com.acme.CustomerBasic"/>
            </parameter>
            <return-value>
                <valid/>
                <convert-group from="javax.validation.groups.Default" to="com.acme.CustomerBasic"/>
            </return-value>
        </constructor>

        <method name="update">
            <parameter type="java.lang.String">
                <valid/>
                <convert-group from="javax.validation.groups.Default" to="com.acme.CustomerBasic"/>
            </parameter>
            <return-value>
                <valid/>
                <convert-group from="javax.validation.groups.Default" to="com.acme.CustomerBasic"/>
            </return-value>
        </constructor>
    </bean>
</constraint-mappings>

8.1.2. Overriding constraint definitions in XML

A constraint definition (i.e. the annotation representing a constraint), cannot be fully expressed in XML but the list of ConstraintValidators associated to a given constraint can be altered.

A constraint definition is represented by a constraint-definition element. The annotation attribute represents the constraint annotation being altered. The validated-by elements represent the (ordered) list of ConstraintValidator implementations associated to the constraint.

If include-existing-validator is set to false, ConstraintValidator defined on the constraint annotation are ignored. If set to true, the list of ConstraintValidators described in XML are concatenated to the list of ConstraintValidator described on the annotation to form a new array of ConstraintValidator evaluated. Annotation based ConstraintValidator come before XML based ConstraintValidators in the array. The new list is returned by ConstraintDescriptor.getConstraintValidatorClasses().

Example 8.9. Overriding constraint definitions

<?xml version="1.0" encoding="UTF-8"?>
<constraint-mappings
        xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/mapping validation-mapping-1.1.xsd"
        version="1.1">
   <default-package>com.acme.app.domain</default-package>
   <bean class="com.acme.common.model.Address">
       [...]
    </bean>

    <constraint-definition annotation="javax.validation.constraints.Size">
        <validated-by include-existing-validators="true">
            <value>com.acme.app.constraint.SizeValidatorForDictionary</value>
        </validated-by>
    </constraint-definition>
    <constraint-definition annotation="AcmeOrderNumber">
        [...]
    </constraint-definition>
</constraint-mappings>

8.1.3. Converting the string representation of a value

Primitive types, Class and Enum are represented as strings in the XML descriptor. Elements of an array are represented by the value element.

byte are represented according to the rules defined in Byte.parseByte(String).

short are represented according to the rules defined in Short.parseShort(String).

int are represented according to the rules defined in Integer.parseInt(String).

long are represented according to the rules defined in Long.parseLong(String).

float are represented according to the rules defined in Float.parseFloat(String).

double are represented according to the rules defined in Double.parseDouble(String).

boolean are represented according to the rules defined in Boolean.parseBoolean(String).

char are represented according to the following rules:

  • the string must be of one character long

  • the character extracted from the string is the returned char

A Class is represented by the fully qualified class name of the class or more precisely according to the syntax described in the documentation of java.lang.Class.getName(). Note that if the raw string is unqualified, default package is taken into account.

An enum is represented by its enum.name() value.

If any of the string representation does not match its type counterpart, a ValidationException is raised.

8.1.4. XML Schema

This section contains the XML schema used for constraint mapping descriptors.

From Bean Validation revision 1.1 onwards, mapping authors must specify the used version of the schema within the version attribute of the constraint-mappings element. Implementations supporting Bean Validation 1.1 must properly parse mapping descriptors of Bean Validation 1.0 and 1.1. If the version attribute attribute is not given, schema version 1.0 is to be assumed by the Bean Validation Provider.

In case an unknown version is given (e.g. if a mapping descriptor adhering to a future schema version is parsed by a Bean Validation 1.1 provider) a ValidationException is raised.

Example 8.10. XML schema for constraint mapping descriptors

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema attributeFormDefault="unqualified"
           elementFormDefault="qualified"
           targetNamespace="http://jboss.org/xml/ns/javax/validation/mapping"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:map="http://jboss.org/xml/ns/javax/validation/mapping"
           version="1.1">

    <xs:annotation>
        <xs:documentation><![CDATA[
            This is the XML Schema for Bean Validation constraint mapping files.

            Bean Validation constraint mapping files must indicate the Bean Validation
            XML schema by using the constraint mapping namespace:

            http://jboss.org/xml/ns/javax/validation/mapping

            and indicate the version of the schema by using the version attribute
            as shown below:

            <constraint-mappings
                xmlns="http://jboss.org/xml/ns/javax/validation/mapping"
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                xsi:schemaLocation="
                    http://jboss.org/xml/ns/javax/validation/mapping
                    validation-mapping-1.1.xsd"
                version="1.1">
                [...]
            </constraint-mappings>
        ]]>
        </xs:documentation>
    </xs:annotation>

    <xs:element name="constraint-mappings" type="map:constraint-mappingsType"/>

    <xs:complexType name="payloadType">
        <xs:sequence>
            <xs:element type="xs:string" name="value" maxOccurs="unbounded" minOccurs="0"/>
        </xs:sequence>
    </xs:complexType>
    <xs:complexType name="groupsType">
        <xs:sequence>
            <xs:element type="xs:string" name="value" maxOccurs="unbounded" minOccurs="0"/>
        </xs:sequence>
    </xs:complexType>
    <xs:complexType name="groupSequenceType">
        <xs:sequence>
            <xs:element type="xs:string" name="value" maxOccurs="unbounded" minOccurs="0"/>
        </xs:sequence>
    </xs:complexType>
    <xs:complexType name="groupConversionType">
        <xs:attribute type="xs:string" name="from" use="required"/>
        <xs:attribute type="xs:string" name="to" use="required"/>
    </xs:complexType>
    <xs:complexType name="constraint-mappingsType">
        <xs:sequence>
            <xs:element type="xs:string" name="default-package" minOccurs="0"/>
            <xs:element type="map:beanType"
                        name="bean"
                        maxOccurs="unbounded"
                        minOccurs="0"/>
            <xs:element type="map:constraint-definitionType"
                        name="constraint-definition"
                        maxOccurs="unbounded"
                        minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="version" type="map:versionType" fixed="1.1" use="required"/>
    </xs:complexType>
    <xs:simpleType name="versionType">
        <xs:restriction base="xs:token">
            <xs:pattern value="[0-9]+(\.[0-9]+)*"/>
        </xs:restriction>
    </xs:simpleType>
    <xs:complexType name="validated-byType">
        <xs:sequence>
            <xs:element type="xs:string" name="value" maxOccurs="unbounded" minOccurs="0"/>
        </xs:sequence>
        <xs:attribute type="xs:boolean" name="include-existing-validators" use="optional"/>
    </xs:complexType>
    <xs:complexType name="constraintType">
        <xs:sequence>
            <xs:element type="xs:string" name="message" minOccurs="0"/>
            <xs:element type="map:groupsType"
                        name="groups"
                        minOccurs="0"/>
            <xs:element type="map:payloadType"
                        name="payload"
                        minOccurs="0"/>
            <xs:element type="map:elementType"
                        name="element"
                        maxOccurs="unbounded"
                        minOccurs="0"/>
        </xs:sequence>
        <xs:attribute type="xs:string" name="annotation" use="required"/>
    </xs:complexType>
    <xs:complexType name="elementType" mixed="true">
        <xs:sequence>
            <xs:element type="xs:string" name="value" maxOccurs="unbounded" minOccurs="0"/>
            <xs:element type="map:annotationType"
                        name="annotation"
                        maxOccurs="unbounded"
                        minOccurs="0"/>
        </xs:sequence>
        <xs:attribute type="xs:string" name="name" use="required"/>
    </xs:complexType>
    <xs:complexType name="classType">
        <xs:sequence>
            <xs:element type="map:groupSequenceType"
                        name="group-sequence"
                        minOccurs="0"/>
            <xs:element type="map:constraintType"
                        name="constraint"
                        maxOccurs="unbounded"
                        minOccurs="0"/>
        </xs:sequence>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
    <xs:complexType name="beanType">
        <xs:sequence>
            <xs:element type="map:classType"
                        name="class"
                        minOccurs="0">
            </xs:element>
            <xs:element type="map:fieldType"
                        name="field"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:getterType"
                        name="getter"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:constructorType"
                        name="constructor"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:methodType"
                        name="method"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute type="xs:string" name="class" use="required"/>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
    <xs:complexType name="annotationType">
        <xs:sequence>
            <xs:element type="map:elementType"
                        name="element"
                        maxOccurs="unbounded"
                        minOccurs="0"/>
        </xs:sequence>
    </xs:complexType>
    <xs:complexType name="getterType">
        <xs:sequence>
            <xs:element type="xs:string" name="valid" minOccurs="0" fixed=""/>
            <xs:element type="map:groupConversionType"
                        name="convert-group"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:constraintType"
                        name="constraint"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute type="xs:string" name="name" use="required"/>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
    <xs:complexType name="methodType">
        <xs:sequence>
            <xs:element type="map:parameterType"
                        name="parameter"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:crossParameterType"
                        name="cross-parameter"
                        minOccurs="0"
                        maxOccurs="1"/>
            <xs:element type="map:returnValueType"
                        name="return-value"
                        minOccurs="0"
                        maxOccurs="1"/>
        </xs:sequence>
        <xs:attribute type="xs:string" name="name" use="required"/>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
    <xs:complexType name="constructorType">
        <xs:sequence>
            <xs:element type="map:parameterType"
                        name="parameter"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:crossParameterType"
                        name="cross-parameter"
                        minOccurs="0"
                        maxOccurs="1"/>
            <xs:element type="map:returnValueType"
                        name="return-value"
                        minOccurs="0"
                        maxOccurs="1"/>
        </xs:sequence>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
    <xs:complexType name="parameterType">
        <xs:sequence>
            <xs:element type="xs:string" name="valid" minOccurs="0" fixed=""/>
            <xs:element type="map:groupConversionType"
                        name="convert-group"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:constraintType"
                        name="constraint"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute type="xs:string" name="type" use="required"/>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
    <xs:complexType name="returnValueType">
        <xs:sequence>
            <xs:element type="xs:string" name="valid" minOccurs="0" fixed=""/>
            <xs:element type="map:groupConversionType"
                        name="convert-group"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:constraintType"
                        name="constraint"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
    <xs:complexType name="crossParameterType">
        <xs:sequence>
            <xs:element type="map:constraintType"
                        name="constraint"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
    <xs:complexType name="constraint-definitionType">
        <xs:sequence>
            <xs:element type="map:validated-byType"
                        name="validated-by"/>
        </xs:sequence>
        <xs:attribute type="xs:string" name="annotation" use="required"/>
    </xs:complexType>
    <xs:complexType name="fieldType">
        <xs:sequence>
            <xs:element type="xs:string" name="valid" minOccurs="0" fixed=""/>
            <xs:element type="map:groupConversionType"
                        name="convert-group"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
            <xs:element type="map:constraintType"
                        name="constraint"
                        minOccurs="0"
                        maxOccurs="unbounded"/>
        </xs:sequence>
        <xs:attribute type="xs:string" name="name" use="required"/>
        <xs:attribute type="xs:boolean" name="ignore-annotations" use="optional"/>
    </xs:complexType>
</xs:schema>

8.2. Configuration schema

XML Configuration is set in META-INF/validation.xml. The file is optional. The XML schema followed by the configuration file is as followed.

Example 8.11. XML configuration XSD

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema attributeFormDefault="unqualified"
           elementFormDefault="qualified"
           targetNamespace="http://jboss.org/xml/ns/javax/validation/configuration"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:config="http://jboss.org/xml/ns/javax/validation/configuration"
           version="1.1">

    <xs:annotation>
        <xs:documentation><![CDATA[
            This is the XML Schema for the Bean Validation configuration file.
            The configuration file must be named "META-INF/validation.xml".

            Bean Validation configuration files must indicate the Bean Validation
            XML schema by using the validation namespace:

            http://jboss.org/xml/ns/javax/validation/configuration

            and indicate the version of the schema by using the version attribute
            as shown below:

            <validation-config
                xmlns="http://jboss.org/xml/ns/javax/validation/configuration"
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                xsi:schemaLocation="
                    http://jboss.org/xml/ns/javax/validation/configuration
                    validation-configuration-1.1.xsd"
                version="1.1">
                [...]
            </validation-config>
        ]]>
        </xs:documentation>
    </xs:annotation>

    <xs:element name="validation-config" type="config:validation-configType"/>
    <xs:complexType name="validation-configType">
        <xs:sequence>
            <xs:element type="xs:string" name="default-provider" minOccurs="0"/>
            <xs:element type="xs:string" name="message-interpolator" minOccurs="0"/>
            <xs:element type="xs:string" name="traversable-resolver" minOccurs="0"/>
            <xs:element type="xs:string" name="constraint-validator-factory" minOccurs="0"/>
            <xs:element type="xs:string" name="parameter-name-provider" minOccurs="0"/>
            <xs:element type="config:executable-validationType" name="executable-validation" minOccurs="0"/>
            <xs:element type="xs:string" name="constraint-mapping" maxOccurs="unbounded" minOccurs="0"/>
            <xs:element type="config:propertyType" name="property" maxOccurs="unbounded" minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="version" type="config:versionType" fixed="1.1" use="required"/>
    </xs:complexType>

    <xs:complexType name="executable-validationType">
        <xs:sequence>
            <xs:element type="config:default-validated-executable-typesType" name="default-validated-executable-types" minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="enabled" use="optional" type="xs:boolean" default="true"/>
    </xs:complexType>
    <xs:complexType name="default-validated-executable-typesType">
        <xs:sequence>
            <xs:element name="executable-type" maxOccurs="unbounded" minOccurs="1">
                <xs:simpleType>
                    <xs:restriction base="xs:string">
                        <xs:enumeration value="NONE"/>
                        <xs:enumeration value="CONSTRUCTORS"/>
                        <xs:enumeration value="NON_GETTER_METHODS"/>
                        <xs:enumeration value="GETTER_METHODS"/>
                        <xs:enumeration value="ALL"/>
                    </xs:restriction>
                </xs:simpleType>
            </xs:element>
        </xs:sequence>
    </xs:complexType>
    <xs:complexType name="propertyType">
        <xs:simpleContent>
            <xs:extension base="xs:string">
                <xs:attribute name="name" use="required" type="xs:string"/>
            </xs:extension>
        </xs:simpleContent>
    </xs:complexType>
    <xs:simpleType name="versionType">
        <xs:restriction base="xs:token">
            <xs:pattern value="[0-9]+(\.[0-9]+)*" />
        </xs:restriction>
    </xs:simpleType>
</xs:schema>

From Bean Validation revision 1.1 onwards, the used version of the schema must be specified within the version attribute of the validation-config element. Implementations supporting Bean Validation 1.1 must properly parse configuration descriptors of Bean Validation 1.0 and 1.1. If the version attribute attribute is not given, schema version 1.0 is to be assumed by the Bean Validation Provider.

In case an unknown version is given a ValidationException is raised.

See Section 5.5.6, “XML configuration: META-INF/validation.xml” for more information on XML based configuration.

Chapter 9. Exception model

Illegal arguments passed to the Bean Validation APIs generally lead to an IllegalArgumentException (see the JavaDoc for specific details). Other exceptions raised by Bean Validation are or inherit from the runtime exception javax.validation.ValidationException. Exception cases are described in their respective sections but include (non exhaustive list):

  • invalid constraint definitions (missing mandatory elements, illegal composition cycle, illegal attribute overriding, etc)

  • invalid constraint declarations (ConstraintValidator implementation matching failure, etc)

  • invalid group definition (circularity)

  • invalid Default group redefinition for classes (missing class group etc)

  • invalid group conversion definitions

  • error when retrieving, initializing, executing ConstraintValidators

  • error when parsing the XML configuration or mappings

  • multiple XML configuration files found

  • missing expected provider or no default provider found

  • missing no-arg constructor on extension implementations described in XML configuration files

  • same entity described more than once across the XML mapping files

  • same property or field described more than once for a given entity in the XML mapping files

  • class, field or getter declared in XML mapping files but not found

  • illegal XML constraint definition

  • illegal XML constraint declaration

  • exception raised either at initialization time or execution time by any of the extension interfaces

Each of these error cases lead to a ValidationException or a subclass of ValidationException (see following subsections).

Every (runtime) exception raised either at initialization time or execution time by any of the extension interfaces (ConstraintValidator, ConstraintValidatorFactory, MessageInterpolator, TraversableResolver, ValidationProviderResolver, ParameterNameProvider) is wrapped in a ValidationException.

If a constraint definition or constraint declaration is invalid for a given class, the metadata API should raise the according exception.

9.1. Error report: ConstraintViolationException

Some frameworks or applications need to convey the result of a validation by raising an exception if the validation returns constraint violations.

Bean Validation provides a reference exception for such cases. Frameworks and applications are encouraged to use ConstraintViolationException as opposed to a custom exception to increase consistency of the Java platform. The exception can be raised directly or wrapped into the framework or application specific parent exception.

Example 9.1. ConstraintViolationException

/**
 * Reports the result of constraint violations.
 *
 * @author Emmanuel Bernard
 * @author Gunnar Morling
 */
public class ConstraintViolationException extends ValidationException {
    [...]

    /**
     * Creates a constraint violation report.
     *
     * @param message error message
     * @param constraintViolations {@code Set} of {@link ConstraintViolation}
     */
    public ConstraintViolationException(String message,
                                        Set<? extends ConstraintViolation<?>> constraintViolations) {
        [...]
    }

    /**
     * Creates a constraint violation report.
     *
     * @param constraintViolations {@code Set} of {@link ConstraintViolation}
     */
    public ConstraintViolationException(Set<? extends ConstraintViolation<?>> constraintViolations) {
        [...]
    }

    /**
     * Set of constraint violations reported during a validation.
     *
     * @return {@code Set} of {@link ConstraintViolation}
     */
    public Set<ConstraintViolation<?>> getConstraintViolations() {
        [...]
    }
}

The ConstraintViolationException carries a Set of ConstraintViolation.

Note

Bean Validation never raises this exception itself. Other frameworks like Java Persistence 2 or interception framework wiring method validation do.

Note

If this exception is meant to be send remotely, ConstraintViolation objects should be Serializable as defined an explained in Section 5.2, “ConstraintViolation”.

9.2. Constraint definition: ConstraintDefinitionException

If a constraint definition does not respect the Bean Validation rules or is inconsistent, a ConstraintDefinitionException is raised. ConstraintDefinitionException is a subclass of ValidationException.

This exception can be raised during validation or when the metadata model for the class hosting this constraint is requested.

Note

These exception cases can be determined at compile time by a tool such as an annotation processor.

9.3. Constraint declaration: ConstraintDeclarationException and UnexpectedTypeException

When a constraint declaration is illegal, ConstraintDeclarationException is raised. This includes amongst other things incorrect group conversion rules (definition or positioning) and illegal method constraint declarations (e.g. inheritance rules, cross-parameter constraint used in an illegal situation, improper use of validationAppliesTo).

ConstraintDeclarationException is a subclass of ValidationException.

When the return type of a property cannot be processed for a given constraint an UnexpectedTypeException is raised. This problem typically arise when either no ConstraintValidator or too many ConstraintValidators match the return type (see Section 4.6.4, “ConstraintValidator resolution algorithm”).

UnexpectedTypeException is a subclass of ConstraintDeclarationException.

This exception can be raised during validation or when the metadata model for the class hosting this constraint is requested.

Note

These exception cases can be determined at compile time by a tool such as an annotation processor.

9.4. Group definition: GroupDefinitionException

When a group definition is illegal, GroupDefinitionException is raised. This typically arises when a cyclic group dependency is discovered, an illegal attribute overriding is defined etc.

GroupDefinitionException is a subclass of ValidationException.

Note

These exception cases can be determined at compile time by a tool such as an annotation processor.

Chapter 10. Integration

In this chapter, integration points between Bean Validation and other technologies are discussed. We first address the integration in generic terms applying to all integrations and we then detail how integration with various Java EE specifications is handled more specifically.

10.1. General requirements

This section covers general requirements that should be followed by any container and interception technology integrating Bean Validation.

10.1.1. Objects lifecycle

Generally speaking, containers and frameworks controlling the life cycle of objects (such as Java EE, dependency injection frameworks or component frameworks) should:

  • build and bootstrap the ValidatorFactory instance for an application.

  • provide access to the ValidatorFactory instance as well as Validator instances in their default configuration using the paradigm of the container: for example, such instances would be injectable in other objects via a dependency injection framework.

  • configure ValidatorFactory with a custom ConstraintValidatorFactory instance that returns managed ConstraintValidator instances, unless a custom ConstraintValidatorFactory is requested by the user. The scope of ConstraintValidator instances is still fully controlled by the Bean Validation provider as described in Section 3.5, “The ConstraintValidatorFactory”, but as managed beans they can receive expected services like injection of other objects.

  • configure ValidatorFactory with managed instances of ConstraintValidatorFactory, MessageInterpolator, ParameterNameProvider and TraversableResolver, if such instances are defined in the XML deployment descriptor. Services provided by the container (like dependency injection) should thus be available to these instances.

  • invoke ValidatorFactory.close() when the ValidatorFactory instance is no longer needed.

  • dispose of managed instances provided to the Bean Validation bootstrap process after ValidatorFactory.close() has been invoked.

Important

In this context, a default ValidatorFactory is a factory configured like the factory returned by Validation.buildDefaultValidatorFactory (see also Section 5.5.5, “Validation”) except for the enhancements described above. A default Validator instance is a Validator instance retrieved via getValidator() from the default ValidatorFactory.

10.1.2. Method and constructor validation

This section expresses the behavior that integration with interception frameworks should follow. Any deviation should be considered with care as it will surprise Bean Validation users.

Method interception frameworks (such as AOP or interceptor frameworks) enable interception of constrained methods following the steps defined in Section 5.4, “Triggering method validation”. Method validation execution is implicit for any method or constructor annotated with constraints.

By default, method validation is applied to all constrained methods or constructors provided the integration technology can intercept the call. By default, getters (as defined in Section 4.1, “Requirements on classes to be validated”) are not considered constrained methods. Static methods are ignored by validation. Putting constraints on a static method is not portable.

Bean Validation - via the interception technology - offers a way to customize whether or not a constructor, method or getter is validated when executed. This is achieved:

Note

Integration layers can read the list of validated executable types defined in the global configuration as well as read whether or not executable validation is disabled via the Configuration object: configuration.getBootstrapConfiguration().getDefaultValidatedExecutableTypes() and configuration.getBootstrapConfiguration().isExecutableValidationEnabled() respectively. This list is extracted from validation.xml.

More formally, a given executable (constructor or method) is validated upon execution according to the following rules in decreasing order:

  • the executable is validated if it is annotated with @ValidateOnExecution and the type attribute contains the executable type or IMPLICIT. If the type attribute does neither contain the executable type nor IMPLICIT, the executable is not validated.

  • otherwise the executable is validated if the type (class, interface) on which it is declared is annotated with @ValidateOnExecution and the type attribute contains the executable type. If the type attribute contains IMPLICIT, then this rule is ignored and the behavior is equivalent to @ValidateOnExecution not being present. If the type attribute does not contain the executable type, the executable is not validated.

  • otherwise the executable is validated if the global executable validation setting contains the executable type. If the global setting does not contain the executable type, the executable is not validated.

  • The rules above do not apply to methods overriding a superclass method or implementing an interface method. In this case, the method inherits the behavior of the method it overrides / implements. Out of the box, a conforming integration implementation raises a ValidationException if the overriding / implementing method hosts the @ValidateOnExecution annotation.

The last point is present to enforce the Liskov substitution principle (more info at Section 4.5.5, “Method constraints in inheritance hierarchies”) In addition, providers may implement alternative, potentially more liberal, approaches for handling validated methods in inheritance hierarchies. Possible means for activating such alternative behavior include provider-specific configuration properties or annotations. Note that client code relying on such alternative behavior is not portable.

The following executable types are available:

  • NONE: parameters and return values are not validated upon execution. This option is equivalent to an empty list of executable types and is present to improve readability. A list containing NONE and other types of executables is equivalent to a list containing the types of executables without NONE.

  • CONSTRUCTORS: parameters and return values are validated provided the executable is a constructor.

  • NON_GETTER_METHODS: parameters and return values are validated provided the executable is a method but not a getter.

  • GETTER_METHODS: return values are validated provided the executable is a getter method.

  • ALL: parameters and return values are validated for all executables (getters, non getters and constructors). This option is equivalent to a list of all executable types and is present to improve readability. A list containing ALL and other types of executables is equivalent to a list containing only ALL.

  • IMPLICIT: if @ValidateOnExecution is on a type (class or interface), then it is equivalent to @ValidateOnExecution not being present; if @ValidateOnExecution is on a an executable, the following applies:

    • if on a constructor, it is equivalent to CONSTRUCTORS.

    • if on a non-getter method, it is equivalent to NON_GETTER_METHODS.

    • if on a getter, it is equivalent to GETTER_METHODS.

Mixing IMPLICIT and other executable types is illegal.

Example 10.1. @ValidateOnExecution annotation

package javax.validation.executable;

/**
 * Expresses which executables (methods or constructors) should have their parameters
 * and return value validated upon execution. Can be on executable (method, constructor)
 * or type level (with the former taking precedence).
 * <p/>
 * If not present for a given executable, the default configuration from
 * {@code META-INF/validation.xml} and finally the implicit default
 * validated executable types (constructors and non-getters) are taken into account to determine
 * whether a given executable is validated upon execution or not.
 * <p/>
 * The following describes the formal rules for deciding whether an executable is validated.
 * They are applied in decreasing order:
 * <ul>
 *     <li>the executable is validated if it is annotated with {@code @ValidateOnExecution} and
 *     the {@code type} attribute contains the executable type or {@link ExecutableType#IMPLICIT}.
 *     If the {@code type} attribute does neither contain the executable type nor {@code IMPLICIT},
 *     the executable is not validated.</li>
 *     <li>otherwise the executable is validated if the type (class, interface) on which it is
 *     declared is annotated with {@code @ValidateOnExecution} and the {@code type} attribute
 *     contains the executable type. If the {@code type} attribute contains
 *     {@code IMPLICIT}, then this rule is ignored and the behavior is
 *     equivalent to {@code ValidateOnExecution} not being present. If the
 *     {@code type} attribute does not contain the executable type, the executable is not
 *     validated.</li>
 *     <li>otherwise the executable is validated if the global executable validation setting
 *     contains the executable type. If the global setting does not contain the executable type,
 *     the executable is not validated.</li>
 *     <li>The rules above do not apply to methods overriding a superclass method or
 *     implementing an interface method. In this case, the method inherits the behavior
 *     of the method it overrides or implements. Out of the box, a conforming implementation
 *     raises a {@link ValidationException} if the overriding / implementing method hosts
 *     the {@code ValidateOnExecution} annotation.</li>
 * </ul>
 * <p/>
 * Note that you can exclude an executable from validation by making sure the rules above do not match
 * or by annotating the executable with {@code @ValidateOnExecution(NONE)}.
 *
 * @author Emmanuel Bernard
 * @since 1.1
 */
@Target({ CONSTRUCTOR, METHOD, TYPE, PACKAGE })
@Retention(RUNTIME)
public @interface ValidateOnExecution {

    /**
     * List of executable types to be validated when called.
     * Defaults to the types discovered implicitly (see {@link ExecutableType#IMPLICIT}).
     */
    ExecutableType[] type() default {ExecutableType.IMPLICIT};
}
package javax.validation.executable;

/**
 * Defines the types of executables targeted by an operation.
 *
 * @author Emmanuel Bernard
 * @since 1.1
 */
public enum ExecutableType {

    /**
     * If the annotation using {@code ExecutableType} is on a type (class or interface),
     * the behavior is equivalent to the annotation not being present.
     * <p/>
     * If on a constructor, it is equivalent to {@link #CONSTRUCTORS}.
     * <p/>
     * If on a non-getter method, it is equivalent to {@link #NON_GETTER_METHODS}.
     * <p/>
     * If on a getter method, it is equivalent to {@link #GETTER_METHODS}.
     */
    IMPLICIT,

    /**
     * None of the executables.
     * <p/>
     * Note that this option is equivalent to an empty list of executable types
     * and is present to improve readability. If {@code NONE} and other types of executables
     * are present in a list, {@code NONE} is ignored.
     */
    NONE,

    /**
     * All constructors.
     */
    CONSTRUCTORS,

    /**
     * All methods except the ones following the getter pattern. A getter according to the
     * JavaBeans specification is a method whose:
     * <ul>
     *     <li>name starts with get, has a return type but no parameter</li>
     *     <li>name starts with is, has a return type and is returning {@code boolean}.</li>
     * </ul>
     */
    NON_GETTER_METHODS,

    /**
    /**
     * All methods following the getter pattern. A getter according to the
     * JavaBeans specification is a method whose:
     * <ul>
     *     <li>name starts with get, has a return type but no parameter</li>
     *     <li>name starts with is, has a return type and is returning {@code boolean}.</li>
     * </ul>
     */
    GETTER_METHODS,

    /**
     * All executables (constructors and methods).
     */
    ALL
}

If a sub type overrides/implements a method originally defined in several parallel types of the hierarchy (e.g. two interfaces not extending each other, or a class and an interface not implemented by said class), @ValidateOnExecution cannot be placed in the parallel types of the hierarchy. This is to avoid an unexpected altering of the post conditions to be guaranteed to the caller.

You can globally disable executable validation by using <executable-validation enabled="false"/>, in this case, <default-validated-executable-types/> and @ValidateOnExecution are ignored.

Example 10.2. validation.xml disabling executable validation

<?xml version="1.0" encoding="UTF-8"?>
<validation-config
        xmlns="http://jboss.org/xml/ns/javax/validation/configuration"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation=
            "http://jboss.org/xml/ns/javax/validation/configuration validation-configuration-1.1.xsd"
        version="1.1">
    <default-provider>com.acme.ACMEProvider</default-provider>
    <message-interpolator>com.acme.ACMEAwareMessageInterpolator</message-interpolator>

    <executable-validation enabled="false"/>

    <constraint-mapping>META-INF/validation/order-constraints.xml</constraint-mapping>
    <constraint-mapping>META-INF/validation/catalog-constraints.xml</constraint-mapping>
    <constraint-mapping>META-INF/validation/customer-constraints.xml</constraint-mapping>

    <property name="com.acme.validation.logging">WARN</property>
    <property name="com.acme.validation.safetyChecking">failOnError</property>

</validation-config>

@ValidateOnExecution(type=IMPLICIT) on a type (class or interface) is useful to mark a class as being involved in executable validation without affecting the behavior. This is used when the integration technology needs a little help to find the classes and interfaces involved.

Note

The proper selection of the validated executables is the responsibility of the integration between the interception technology and Bean Validation. Bean Validation engines ignore the XML configuration around executable validation and @ValidateOnExecution when validating executables and when providing metadata.

10.1.2.1. Examples

The following example shows some of the way you can refine executable validation with @ValidateOnExecution.

Example 10.3. Method validation configurations

//optional: @ValidateOnExecution
public class OrderService {

    boolean isValidCustomer(@NotNull String customerCode) { [...] }

    @ValidateOnExecution
    @Min(0)
    Integer getBacklog() { [...] }

    @ValidateOnExecution(type=NONE)
    Order placeOrder(@NotNull String customerCode, @Valid Item item, int quantity) { [...] }

}

@ValidateOnExecution(type={GETTER_METHODS, NON_GETTER_METHODS})
public class SimpleOrderService extends OrderService {

    public SimpleOrderService(@NotNull ServiceProvider provider) { [...] }

    @Overrides
    Order placeOrder(String customerCode, Item item, int quantity) { [...] }

}

//optional: @ValidateOnExecution
public class ComplexOrderService extends SimpleOrderService {
    public ComplexOrderService(@NotNull ServiceProvider provider) { [...] }
}

All constructors and non-getter methods of OrderService are validated upon execution as this is the default setting. isValidCustomer() is validated as this method is not a getter (it has a parameter). getBacklog() is a getter but is validated thanks to @ValidateOnExecution defaulting to GETTER_METHODS. placeOrder() is not validated as @ValidateOnExecution is set to NONE.

All getter and non-getter methods of SimpleOrderService are validated upon execution by default due to the presence of @ValidateOnExecution on the class. The SimpleOrderService constructor is thus not validated. SimpleOrderService.placeOrder() is not validated either because it overrides OrderService.placeOrder() and thus inherits its settings.

All constructors and non-getter methods of ComplexOrderService are validated upon execution as this is the default settings - the type level settings of SimpleOrderService are not inherited. This means that the ComplexOrderService constructor is validated.

@ValidateOnExecution can be optionally set on OrderService and ComplexOrderService without altering the semantic. This marker is necessary for some integration technology in some situations.

10.2. Java EE

Java EE must obey the rules defined above and make the following instances available under JNDI:

  • ValidatorFactory under java:comp/ValidatorFactory

  • Validator under java:comp/Validator

Instead of looking the instances up via JNDI, the user can request them to be injected via the Resource annotation:

@Resource ValidatorFactory validatorFactory;
@Resource Validator validator;

When the application is CDI enabled, the ValidatorFactory and Validator instances returned by JNDI or @Resource injection are CDI enhanced as defined in Section 10.3, “Context and Dependency Injection (CDI) integration”. In particular, dependency injection is available to Bean Validation components.

10.3. Context and Dependency Injection (CDI) integration

There are several integrations points between Bean Validation and CDI. If a Bean Validation provider integrates with CDI, it must follow the rules laid out in this section. In a Java EE container, a Bean Validation provider must integrate with CDI.

10.3.1. ValidatorFactory and Validator

Similar to the Java EE integration via @Resource (see Section 10.2, “Java EE”), a CDI container must support injection of built-in default ValidatorFactory and Validator beans via @Inject. These default beans are injectable via the @Default qualifier.

@Inject ValidatorFactory;
@Inject Validator;

Optionally, the CDI container can support injection of provider specific - as defined by Validation.byProvider() - ValidatorFactory and Validator beans via @Inject. These beans must be registered with a custom qualifier, for example @ACME. Using the product name or brand for the qualifier is considered good practice.

@Inject @ACME ValidatorFactory;
@Inject @ACME Validator;

Discussion on possible implementations

Registration of the built-in default beans and the provider specific beans may be achieved using the CDI portable extension SPI or a vendor specific SPI.

10.3.2. ConstraintValidatorFactory, MessageInterpolator, ParameterNameProvider and TraversableResolver

If a custom ConstraintValidatorFactory, MessageInterpolator, ParameterNameProvider or TraversableResolver class is defined in the XML deployment descriptor (see Section 5.5.6, “XML configuration: META-INF/validation.xml”), the ValidatorFactory must be configured with CDI managed beans representing the requested classes. Services like dependency injection, interception and decoration must thus be made available to these instances by the container.

If no custom ConstraintValidatorFactory is requested by the user, the ValidatorFactory must be configured with a custom ConstraintValidatorFactory instance that returns CDI managed beans representing the requested ConstraintValidator types. The factory

  • creates non-contextual ConstraintValidator instances for each ConstraintValidatorFactory.getInstance() call. To inject dependencies into the ConstraintValidator instance, the CDI InjectionTarget API should be used. Before returning the instance the following calls should be made: InjectionTarget.produce(), InjectionTarget.inject() and InjectionTarget.postConstruct().

  • calls InjectionTarget.preDestroy() and InjectionTarget.dispose() upon ConstraintValidatorFactory.releaseInstance (see also Section 3.5, “The ConstraintValidatorFactory” for more information about the life cycle of a ConstraintValidator).

Using directly or indirectly a JPA EntityManager that might call back Bean Validation for validation is not allowed in the Bean Validation extension points and in ConstraintValidator instances. This would lead to infinite flush or unexpected behavior.

10.3.3. Method and constructor validation

Bean Validation requires that CDI beans support constructor and method validation as defined in Section 10.1.2, “Method and constructor validation”. Validation must happen at the equivalent time an interceptor occurs when having priority Interceptor.Priority.PLATFORM_AFTER+800, in other words priority of 4800.

For maximum portability, it is recommended to mark CDI bean interfaces and classes involved in executable validation with @ValidateOnExecution (defaults to IMPLICIT). This helps some implementations to be more efficient. Most CDI - Bean Validation integration implementations do not need such marker. In particular this marker should not be needed on validated beans annotated with constraint annotations, @Valid or @ValidateOnExecution anywhere in the class. Such limitation will be removed in a future version of this specification.

Discussion on possible implementations

The CDI interceptor binding facility does not directly support this, but the effect may be achieved using the CDI portable extension SPI, or vendor specific SPIs. For example, an interceptor with the expected priority can be programmatically bound to the constructors and methods expected to be validated according to the rules at Section 10.1.2, “Method and constructor validation”.

It is recommended to only intercept methods and constructors that are both constrained and validated according to the rules defined at Section 10.1.2, “Method and constructor validation”. Section 5.4, “Triggering method validation” gives examples how the metadata API can be used to determine whether or not a method is constrained (regardless of the filtering rules of @ValidateOnExecution).

10.4. Java Persistence 2.0 integration

Integration with Java Persistence is described in the Java Persistence 2 specification (JSR-317 and later JSR-338). Persistence frameworks are encouraged to mimic the integration work done with Java Persistence.

10.5. Java Server Faces 2.0 integration

Integration with Java Server Faces is described in the Java Server Faces 2 specification (JSR-314 and later JSR-344). Presentation frameworks are encouraged to study the integration work done with JSF 2.

10.6. JAX-RS 2 integration

Integration with JAX-RS is described in the JAX-RS 2 specification (JSR-339).

Appendix A. Terminology

This appendix aims at giving an overview on the different key terms used through this specification. They are not to be considered formal definitions. Formal definitions are to be inferred from the core specification.

Table A.1. terminology

TermDefinition
ConstraintA restriction on a bean instance, the value of a field or the value of a JavaBean property
Constraint declarationAssignment of a constraint to a target (bean, field, property) for a specific class. Typically by declaring an annotation on the target but can also be done through a XML deployment descriptor
Validation routine

Sequence of operations executed by the Bean Validation provider to validate a given object graph

Constraint definitionDefines a type of constraint, its attributes and the actual constraint validation implementations. Done through annotations. The list of constraint validation implementations can be provided via XML
groupConstraints can belong to one or more group or context. Useful to apply a subset of the constraints for a given use case. By default, the Default group is used.
group sequenceDefines a group ordering in the validation process. If a given group in the sequence contains one or more failure, the following groups in the sequence must be ignored.
Constraint validationConstraint logic algorithm used to determine whether a given value passes a constraint or not.
Constraint validation implementationClass implementing the constraint logic and used to determine whether a given value pass a constraint or not.
Bean validation providerProduct implementing this specification
Message interpolatorAlgorithm used to build the end user message associated to a constraint failure. Typically useful for i18n
Constraint metadata APIAPI exposing the constraints applied to a given bean type. Also considered one of the integration points with other JSR or frameworks.
Bootstrap APIBootstrapping part of the Bean Validation API producing a ValidatorFactory.
javax.validation.ConstraintValidatorInterface implemented by a constraint validation implementation
Composing constraintConstraint declared on another constraint definition. When the main constraint is validated, the composing constraints are validated too.
javax.validation.ValidatorMain API. Holds contracts to validate object graphs
javax.validation.ConstraintViolationInterface describing a given constraint failure on a given bean
Getter

Method whose:

  • name starts with get and has a return type but no parameter

  • name starts with is, has no parameter and is returning boolean

Appendix B. Standard ResourceBundle messages

The properties listed below are resolved by the default message interpolator.

javax.validation.constraints.AssertFalse.message=must be false
javax.validation.constraints.AssertTrue.message=must be true
javax.validation.constraints.DecimalMax.message=\
    must be less than ${inclusive == true ? 'or equal to ' : ''}{value}
javax.validation.constraints.DecimalMin.message=\
    must be greater than ${inclusive == true ? 'or equal to ' : ''}{value}
javax.validation.constraints.Digits.message=\
    numeric value out of bounds (<{integer} digits>.<{fraction} digits> expected)
javax.validation.constraints.Future.message=must be a future date
javax.validation.constraints.Max.message=must be less than or equal to {value}
javax.validation.constraints.Min.message=must be greater than or equal to {value}
javax.validation.constraints.NotNull.message=must not be null
javax.validation.constraints.Null.message=must be null
javax.validation.constraints.Past.message=must be a past date
javax.validation.constraints.Pattern.message=\
    must match the following regular expression: {regexp}
javax.validation.constraints.Size.message=size must be between {min} and {max}

Appendix C. Java Persistence 2.0 and schema generation

While not specified by this specification or the Java Persistence 2.0 specification, Persistence Providers are encouraged to make use of Bean Validation constraint metadata when generating DDL schemas. The proposal is as followed.

Ideas explored and not standardized

Java Persistence consumes Bean Validation (BV) metadata to enhance persistence property 
metadata.

A Persistence provider must use the BV metadata of a given list of groups. 
The default group evaluated is Default (default BV group). Groups evaluated 
can be overridden by a property. 
This property contains the comma separated groups (fully qualified class name).

For each entity, apply the following algorithm. 
For each persistent property in a given entity: 
 - extract the list of BV constraints (including the composing constraints) 
 - determine the subset of applicable constraints 
    (i.e. constraints understood by the persistence provider)
 - apply these constraints on the persistent property metadata 
 - if the property type is an embeddable object or a collection 
of embeddable objects, apply the algorithm on the embeddable object properties

The list of constraints that must be understood by persistence providers are
as followed:
 - @NotNull should be considered equivalent to @Column(nullable=false) / 
     @JoinColumn(nullable=false)
 - @Size.max should be considered equivalent to @Column.length 
     for String properties 
 - @Digits (which contains integer and fraction) should be considered 
     equivalent to @Column.precision = integer+fraction, 
     @Column.scale = fraction for decimal columns

The BV annotation metadata should have priority over JPA metadata 
(JPA has no sensible "unset" values on their annotations).

Question: should we add @Unique that would map to @Column(unique=true)? 
@Unique cannot be tested at the Java level reliably but could generate
a database unique constraint generation. @Unique is not part 
of the BV spec today.

Persistence Provider should optionally recognize and try to apply the 
following constraints as well:
 - @Min / @Max on numeric columns (TODO String too?)
 - @Future / @Past on temporal columns
 - @Size for collections and array (not sure it is feasible).

Persistence Providers can also apply non standard constraints to their metadata model. 
For example, provider ACME might recognize and understand @com.acme.validation.Email 
and apply it to the database model.

While most high level constraints will not be recognize, the BV built-in constraints 
will be the common language spoken by Persistence Providers. Any high level constraint 
can be composed of more modular constraints (constraint composition).

* additional proposal
In case of a constraint violation report detected and generated by the database 
(not null, etc), the Java persistence provider catches this report and translates 
it into a BV error report. From the perspective of the application, constraint 
errors are viewed through a unified layer. BV must provide some API to create a 
constraint violation error (constraintDescriptor.createConstraintViolation(...)).

While this proposal has a lot of value-add, I wonder how difficult it can be to 
implement this in persistence providers.

Provide a way to disable BV metadata use by a persistence provider (property based).

This is not an endorsement of the Java Persistence expert group or the Bean Validation expert group. Such approach may nor may not be standardized in the future. Such integration should not be considered portable.

Appendix D. Changelog

Example D.1. Changelog

1.1.0.Final (2013-04-10)
------------------------

** Improvement
    * [BVAL-452] - Remove @Deprecate annotation from addNode() method


1.1.0.CR3 (2013-03-20)
----------------------

** Bug
    * [BVAL-444] - Remove revisionflags from specification
    * [BVAL-445] - Do not consider arrays of primitives equivalent to arrays of wrappers in ConstraintValidation resolution

** Improvement
    * [BVAL-448] - Mention "boolean" instead of "Boolean" in getter definition
    * [BVAL-450] - Make @ValidateOnExecutable for @Override methods raise an exception

** Task
    * [BVAL-449] - Remove tck-needs-update


1.1.0.CR2 (2013-03-14)
----------------------

** Bug
    * [BVAL-431] - Typo in EL expression exemple
    * [BVAL-435] - Rename element <validated-executables/> to <default-validated-executable-types/>
    * [BVAL-436] - Offer global switch to disable executable validation altogether
    * [BVAL-437] - Redesign @ValidateExecutable into @ValidateOnExecution and as CDI marker for portability

** Improvement
    * [BVAL-420] - Add missing @since in metadata package
    * [BVAL-421] - Clarify whether or not getters are provided by the metadata API
    * [BVAL-422] - Update TCK markers
    * [BVAL-423] - Clarify behavior of ConstraintViolation#getLeafBean() for validateValue()
    * [BVAL-424] - Refer to @SupportedValidationTarget in ConstraintValidation JavaDoc
    * [BVAL-429] - Throw a ConstraintDefinitionException if there a several cross-parameter validators
    * [BVAL-432] - Rename areParametersConstrained to hasConstrainedParameters and isReturnValueConstrained to hasConstrainedReturnValue on ExecutableDescriptor
    * [BVAL-433] - Forbid @ValidatedExecutable on methods of parallel hierarchies
    * [BVAL-434] - Clarify exception type if cross-parameter validator support neither Object nor Object[]
    * [BVAL-440] - Improve description of ExecutableType.GETTER_METHODS
    * [BVAL-442] - Make getConstrainedMethods(MethodType methodType, MethodType... methodTypes) to be less error-prone

** New Feature
    * [BVAL-441] - Allow for identical configuration in subtypes

** Task
    * [BVAL-425] - Raise IllegalArgumentException when validateParameters and validateReturnValue are passed parameters that do not match
    * [BVAL-428] - Map remaining assertions for BV 1.1
    * [BVAL-438] - Integration chapter should not mention that the boostrap API can be used to create additional ValidationFactory
    * [BVAL-439] - Clarify that EE validator factory supports CDI services


1.1.0.CR1 (proposed final draft) (2013-02-20)
---------------------------------------------

** Bug
    * [BVAL-322] - Formatting and style improvements
    * [BVAL-369] - Specify copyright year correctly in license headers
    * [BVAL-391] - Use @SupportValidationTarget instead of @CrossParameterConstraint for cross-parameter constraint validators
    * [BVAL-397] - Align the JavaDoc on temps (return vs returns, define vs defines)
    * [BVAL-401] - validateReturnValue should not throw an exception if the method has no return value
    * [BVAL-402] - Remove notion of "reachable" parameters in method validation routine
    * [BVAL-403] - Add example on method validation to 4.6.3. ("Traversable property")
    * [BVAL-407] - ConstraintViolation.unwrap parameterized type hides ConstraintViolation parameterized type

** Improvement
    * [BVAL-275] - Align on style for referencing methods in spec text
    * [BVAL-277] - Align on style for author names in JavaDoc
    * [BVAL-285] - ValidatorFactory#close should clearly state post conditions 
    * [BVAL-350] - Add more examples on how to use methods for validating method and constructor constraints
    * [BVAL-362] - Reference the various specs (JPA, JSF, CDI, JavaBeans)
    * [BVAL-400] - Add xml and exception chapters to the list in "How this document is organized"
    * [BVAL-404] - Path examples in table 5.2 are missing node specific attributes like parameterIndex
    * [BVAL-405] - Clarify what isBeanConstrained does and add hasExecutableConstrained
    * [BVAL-406] - Add ConstraintDescriptor.getValidationAppliesTo() and getMessageTemplate()
    * [BVAL-409] - Make ParameterNameProvider use List instead of arrays
    * [BVAL-410] - Make node creation suppress the cross-param and bean-level node in case of subnode creation
    * [BVAL-412] - Make <convert-group/> follow <valid/> and precede <constraint/> in the mapping XSD
    * [BVAL-413] - Fix method validation and ConstraintViolation example 
    * [BVAL-414] - Add example for metadata API with executables
    * [BVAL-415] - Make sure maven plugins are set in beanvalidation-api
    * [BVAL-417] - Mention "validationAppliesTo" in docs of @SupportedValidationTarget
    * [BVAL-419] - Clarify that using a cross-parameter constraint on a method without parameter is illegal


1.1.0.Beta4 (2013-02-15)
------------------------

** Sub-task
    * [BVAL-316] - Decide on whether to allow validation of static methods or not
    * [BVAL-330] - Refinements around metadata API

** Bug
    * [BVAL-221] - The constraint violation builder cannot put constraint on a top level map key
    * [BVAL-283] - Clarify that ConstraintValidator instances must be destroyed after each method validation call if the ConstraintValidatorFactory is provided to the Validator
    * [BVAL-284] - Clarify that ConstraintValidator instances passed to CVF.releaseInstance must be coming from the CVF creating them
    * [BVAL-326] - Fix metadata and error reports for cross-parameter validation
    * [BVAL-328] - Add recommendation that @Inherited shouldn't be added to constraint annotation types
    * [BVAL-337] - Clarifications around ConstraintViolation for method validation
    * [BVAL-370] - Re-consider how cross-parameter constraints are represented in metadata API and XML descriptors
    * [BVAL-375] - Add dedicated "validationAppliesTo" element to schema type representing constraints
    * [BVAL-378] - Mismatch between enum ExecutableType and corresponding schema type
    * [BVAL-380] - Remove improper sentence around constraint being validated once globally in validation routine
    * [BVAL-381] - Specify which path is pathed to traversable resolvers in case of cascaded method validation
    * [BVAL-388] - Create sub-types of Node instead of Node#getElementDescriptor() and remove ElementDescriptor.getKind()
    * [BVAL-389] - @ValidateExecutable.type should default to ALL and NONE should be renamed OFF
    * [BVAL-390] - Clarify syntax for specifying parameter types in XML
    * [BVAL-393] - Revert "intersection type trick"

** Improvement
    * [BVAL-191] - Introduce a addBeanNode() method to the fluent node builder API
    * [BVAL-269] - Polish support for dependency injection after draft feedback
    * [BVAL-336] - Decide what to do about element descriptor when using constraint violation builder API
    * [BVAL-344] - Improve wording around CDI integration
    * [BVAL-368] - Return constant value from Node#getName() for return value nodes
    * [BVAL-372] - Consider moving ExecutableValidator to the executable subpackage
    * [BVAL-379] - Clarify that modifications to BootstrapConfiguration have no effect
    * [BVAL-384] - Add example for ElementDescriptor#findConstraints() for methods
    * [BVAL-385] - Return void ReturnValueDescriptor from ExecutableDescriptor#getReturnValueDescriptor() for void methods
    * [BVAL-386] - Clarify that CDI integration is mandatory under Java EE only
    * [BVAL-398] - Make validateReturnValue raise ValidationException if the method has no return value

** New Feature
    * [BVAL-329] - Method validation support (III)
    * [BVAL-383] - Add a  unwrap method in ConstraintViolation
    * [BVAL-387] - Add ability to add a node corresponding to a parameter in ConstraintViolationBuilder

** Task
    * [BVAL-394] - Verify that we don't need a spec defined API to expose classes hosting constrained methods or constructor defined in XML


1.1.0.Beta3 (2013-02-01)
------------------------

** Sub-task
    * [BVAL-273] - Extend the XML descriptor schema to represent method-level constraints
    * [BVAL-314] - Provide ability to disable validation for method/constructor validation 

** Bug
    * [BVAL-327] - Provide way to change the executable validation (ie accept getters)
    * [BVAL-342] - Clarify that validateProperty / validateValue does not support property paths 
    * [BVAL-343] - "Provider org.hibernate.validator.HibernateValidator not a subtype" error during service discovery
    * [BVAL-345] - List of messages in the standard resource bundle is incomplete
    * [BVAL-346] - Clarify that getters must have no parameter
    * [BVAL-347] - Add implicit assumptions from TCK to spec text
    * [BVAL-351] - Clarify that EntityManager cannot be injected if validating from JPA
    * [BVAL-361] - Expose group conversions via meta-data API
    * [BVAL-363] - Clarify that super method constraints are considered in the validation routine but not constructors
    * [BVAL-366] - Fix typo on ConfigurationState JavaDoc
    * [BVAL-371] - Add package level javadoc (package-info.java)
    * [BVAL-377] - Provide MessageInterpolator.Context#unwrap to allow for custom extensions 

** Improvement
    * [BVAL-192] - Add 'exclusive' boolean attribute to @DecimalMin/@DecimalMax constraints
    * [BVAL-332] - Specify semantics of @ConvertGroup when given several times at overridden property
    * [BVAL-340] - Denote method parameter constraints at declaration site (vs. at definition site)
    * [BVAL-352] - Clarify what managed means in the integration chapter in particular for CDI
    * [BVAL-359] - Relax contract of ExecutableDescriptor#getParameterDescriptors()
    * [BVAL-360] - Describe IllegalArgumentException for ExecutableValidator methods
    * [BVAL-364] - Clarify whether or not the metadata API ignore the method enable/disable settings
    * [BVAL-365] - Clarifications around group conversion in hierarchies
    * [BVAL-367] - Make clear whether methods/properties inherited from super types are reflected by the meta-data API
    * [BVAL-373] - Move ConvertGroup to the groups subpackage

** New Feature
    * [BVAL-219] - Add support for interpolating the value in error messages
    * [BVAL-223] - Add formatter syntax for interpolated messages via EL expression support
    * [BVAL-249] - Add unwrap method to ConstraintValidatorContext for provider extension
    * [BVAL-333] - Enable configuration of group conversions via XML

** Task
    * [BVAL-338] - Clarify lifecycle of managed objects created by BV povider
    * [BVAL-348] - Add example for illegal group conversion on a return value in an inheritance hierarchy
    * [BVAL-349] - Mark spec sentences as TCK-relevant (1.0 assertions)
    * [BVAL-353] - Mark spec sentences as TCK-relevant (1.1 assertions)
    * [BVAL-354] - Describe tagging of TCK-relevant sentences in README.md
    * [BVAL-355] - Rename Validator#forMethods() to forExecutables()
    * [BVAL-357] - Clarify that traversable resolver is not used on parameter and return values during method validation
    * [BVAL-358] - Make ExecutableDescriptor#validateConstructorParameters() and validateConstructorReturnValue() more usable
    * [BVAL-374] - Clarify exceptional case in section 5.5.5 bootstrapping 
    * [BVAL-376] - Remove @MethodValidated as it is not adding value to the CDI integration


1.1.0.Beta2 (2012-11-27)
------------------------

** Sub-task
    * [BVAL-331] - Establish common super-interface for MethodDescriptor and ConstructorDescriptor


** Bug
    * [BVAL-335] - @ConvertGroup.List is missing target types and retention policy



** Improvement
    * [BVAL-198] - Simplify creation of ConstraintViolationExceptions
    * [BVAL-334] - Refer to CDI provided beans as "built-in" beans


1.1.0.Beta1 (public review draft 1) (2012-10-19)
------------------------------------------------

** Sub-task
    * [BVAL-232] - Support cross-parameter constraints
    * [BVAL-274] - Extend the meta-data API with required convenience methods for method validation
    * [BVAL-290] - Mark new method with @since annotation
    * [BVAL-300] - Clarify behavior of constructor validation in class hierachies 
    * [BVAL-308] - Settle on approach for constraint refinement in sub-types
    * [BVAL-309] - Specify logic to be implemented by method validation interceptors
    * [BVAL-310] - Move methods related to method validation to delegate interface
    * [BVAL-317] - Rename 'method-level validation' with 'method validation'


** Bug
    * [BVAL-296] - Example using ConstraintValidatorContext is incorrect
    * [BVAL-298] - DefaultValidationProviderResolver should check context and current class loader for service file
    * [BVAL-304] - Add OSGi headers in the reference implementation
    * [BVAL-306] - Clarify interceptor order in method validation triggering



** Improvement
    * [BVAL-208] - Support groups translation during cascaded validations 
    * [BVAL-226] - Make clear whether the static or the runtime type should be considered when creating property paths in case of cascaded validations
    * [BVAL-230] - Add support for validating CharSequence types instead of just Strings
    * [BVAL-259] - Evaluation of composed constraints should stops on first validation error in case of @ReportAsSingleViolation
    * [BVAL-281] - Improve message when building a ValidatorFactory but no provider is available in the classpath
    * [BVAL-292] - Clarify the behavior of ConfigurationSource methods when no configuration file is present
    * [BVAL-299] - Add note on required Java version

** New Feature
    * [BVAL-272] - Method validation support (II)
    * [BVAL-295] - Should validation-configuration and validation-mapping xsds define a version attribute


** Task
    * [BVAL-280] - Decide whether DefaultValidationProviderResolver should not throw an exception when a specified provider cannot be loaded
    * [BVAL-307] - Decide how CDI and Bean Validation is integrated


1.1.0.Alpha1 (early draft 1) (2012-03-13)
-----------------------------------------

** Sub-task
    * [BVAL-242] - Extend the meta-data API to represent method-level constraints
    * [BVAL-243] - Provide a means for specifying method parameter names
    * [BVAL-244] - Extend Validator API with methods for method validation
    * [BVAL-245] - Define how method constraints are declared at parameters and return values


** Bug
    * [BVAL-194] - Invalid license info
    * [BVAL-196] - Missing </code> element in Javadocs for ConstraintValidatorContext.ConstraintViolationBuilder.NodeContextBuilder
    * [BVAL-212] - Wrong closing </code> element in javadocs of BeanDescriptor
    * [BVAL-236] - Fails to load META-INF/services provider configuration files on non-ASCII platforms 


** Improvement
    * [BVAL-201] - Fix typo in spec, chapter 4.4.3
    * [BVAL-270] - Specify that Bean Validation 1.1 providers must support deployment descriptors version 1.0

** New Feature
    * [BVAL-238] - Support for container injection in ConstraintValidator
    * [BVAL-241] - Support for method validation
    * [BVAL-258] - Clean introduction section to reflect Bean Validation 1.1
    * [BVAL-263] - Add a close() method to ValidatorFactory
    * [BVAL-265] - Expose settings defined in XML in the Configuration API (for ConstraintValidatorFactory, MessageInterpolator etc)


** Task
    * [BVAL-206] - Update pom to use the new distributationManagement information
    * [BVAL-228] - Prepare specification document and Git repository for public eyes
    * [BVAL-279] - Update POM file for Bean Validation API to use latest Git repo urls and generally be ready for a release


1.0.0 final (2009-10-12)
------------------------

** Bug
    * [BVAL-181] - Fix some namespace issues in validation-configuration-1.0.xsd


** Improvement
    * [BVAL-182] - Add getDefaultTraversableResolver and getDefaultConstraintValidatorFactory to Configuration
    * [BVAL-183] - Add getTraversableResolver and getConstraintValidatorFactory to ValidatorFactory
    * [BVAL-184] - Replace Red Hat Middleware LLC to Red Hat, Inc. and/or its affiliates
    * [BVAL-186] - Clarify method names on the constraint violation builder DSL of ConstraintValidatorContext
    * [BVAL-187] - Imply that ConstraintViolation is serializable if entities are serializable

** New Feature
    * [BVAL-185] - Allow overriding of ConstraintValidatorFactory when creating a Validator
    * [BVAL-190] - Add methods to filter ConstraintDescriptor per groups, target and scope


** Task
    * [BVAL-132] - Define behaviour for BeanDescriptor.getConstraintsForProperty(null)



1.0.CR5 (2009-08-27)
--------------------

** Bug
    * [BVAL-173] - Fix typo getUnorderdConstraintDescriptorsMatchingGroups => getUnorderedConstraintDescriptorsMatchingGroups
    * [BVAL-177] - Payload of composed constraints are ignored, the main constraint payload is propagated
    * [BVAL-178] - Add payload to the XML schema
    * [BVAL-180] - ConstraintDescriptor.getPayload() should return Set<Class<? extends Payload>> not Set<Class<Payload>>


** Improvement
    * [BVAL-174] - clearer default message for assertTrue and assertFalse
    * [BVAL-179] - Rename ConstraintPayload to Payload



1.0.CR4 Unpublished release
---------------------------



1.0.CR3 Proposed Final Draft 2 (2009-07-08)
-------------------------------------------

** Bug
    * [BVAL-144] - validation-configuration.xsd property element does not extend basic string type preventing Oxygen to be happy
    * [BVAL-159] - Fix example 3.8 on object graph validation 


** Improvement
    * [BVAL-143] - Describe path with an object model
    * [BVAL-147] - Support for unbounded wildcards in ConstraintValidator
    * [BVAL-148] - Built-in constraints annotations now annotated with @Constraint(validatedBy={})
    * [BVAL-151] - TraversableResolver#isTraversable can receive null traversableObject when valudateValue is called
    * [BVAL-152] - TraversableResolver should differentiate reachability and cascadability
    * [BVAL-153] - Generify ConstraintValidatorException
    * [BVAL-154] - Iterable is a superclass of all collection, clarify it's interaction with @Valid
    * [BVAL-155] - ignore-annotation is not inherited hierarchically: make that explicit
    * [BVAL-156] - Pattern.Flag takes the JDK flag int at construction time
    * [BVAL-157] - Add [] to non-indexed iterable path 
    * [BVAL-158] - Clarify that @Valid is orthogonal to the idea of group
    * [BVAL-160] - rename message template key as [f.q.c.n of the constraint].message
    * [BVAL-162] - Move metadata classes to the metadata package (BeanDescriptor, ElementDescriptor, PropertyDescriptor, ConstraintDescriptor)
    * [BVAL-164] - Validation.byProvider now accept the provider implementation class
    * [BVAL-166] - IllegalArgumentException raised on BeanDescriptor.getConstraintsForProperty and Validator.getConstraintsForClass
    * [BVAL-167] - Recommend f.q.c.n.message for resource bundle keys and migrate examples
    * [BVAL-169] - Rename ElementDescriptor.getType to getElementClass
    * [BVAL-170] - Let built-in annotations to support ElementType.PARAMETER and ElementType.CONSTRUCTOR

** New Feature
    * [BVAL-149] - Provide access to the ValidationProviderResolver via BootstrapState
    * [BVAL-150] - Add ConstraintViolation.getRootBeanClass
    * [BVAL-161] - Add unwrap methods to ValidatorFactory and Validator
    * [BVAL-163] - Add support for constraint payload
    * [BVAL-168] - Return the list of matching ConstraintDescriptor for a given set of groups
    * [BVAL-172] - Provide ConstraintDescriptor#getPayload



1.0.CR2 Unpublished release
---------------------------



1.0.CR1 Proposed Final Draft (2009-03-16)
-----------------------------------------


** Bug
    * [BVAL-118] - ConstraintDescriptor.getGroups() returns Default if no group is declared on the constraint
    * [BVAL-125] - @Size.min default value should be 0


** Improvement
    * [BVAL-32] - Describe what is happening when a composition is not consistent
    * [BVAL-50] - Be consistent in the spec, use @author or not
    * [BVAL-54] - Specify that constraints on non getter methods are ignored (if BVAL-36 is not accepted)
    * [BVAL-72] - Validating an object multiple times if in a different branch of the graph
    * [BVAL-86] - Default TraversableResolver is JPA aware
    * [BVAL-88] - Improvement on MessageInterpolator
    * [BVAL-91] - Rename Constraint related classes to improve readability
    * [BVAL-95] - @Size should support Map
    * [BVAL-96] - Support byte in @Min/@Max
    * [BVAL-106] - Constraintdescriptor.getConstraintValidatorClasses() should return a List, not an array
    * [BVAL-114] - Relax property names in ConstraintValidatorContext
    * [BVAL-120] - Rename ConstraintViolation getRawMessage=>getMessageTemplate, getInterpolatedMessage=>getMessage
    * [BVAL-122] - Rename @GroupSequence.sequence to @GroupSequence.value
    * [BVAL-126] - Define group sequence logic more formally and eliminate corner cases
    * [BVAL-129] - Clarify ConstraintValidatorContext propertyPath generation
    * [BVAL-130] - Make ConstraintDescriptor generic: ConstraintDescriptor<T extends Annotation>
    * [BVAL-131] - Provide object graph navigation determinism
    * [BVAL-134] - @Valid accepts objects implementing Iterable 
    * [BVAL-135] - Remove DefaultValidationProviderResolver from the public API
    * [BVAL-136] - Add Context object for MessageInterpolator
    * [BVAL-137] - prefix for message template key is constraint. instead of validator.
    * [BVAL-138] - Rename OverridesParameter to OverridesAttribute
    * [BVAL-139] - Remove @OverridesParameters and use the inner class mode (OverridesAttribute.LIst)
    * [BVAL-140] - BeanDescriptor.getConstrainedProperties() returns Set<PropertyDescriptor>
    * [BVAL-141] - Rename ConstraintDescriptor.getParameters() to getAttributes()

** New Feature
    * [BVAL-52] - Define the exception hierarchy and rules
    * [BVAL-55] - Exception policy
    * [BVAL-65] - Additional built-in constraints
    * [BVAL-98] - Type-safe ConstraintValidator
    * [BVAL-100] - Support XML mapping overriding
    * [BVAL-102] - Support META-INF/validation.xml
    * [BVAL-119] - Introduce @Pattern for regexp
    * [BVAL-121] - Define built-in constraints plural forms
    * [BVAL-123] - Add ConstraintViolationException
    * [BVAL-124] - Introduce backslash as escaping character
    * [BVAL-142] - @Min/@max no longer accept float/double and introduce @DecimalMin/@DecimalMax


** Task
    * [BVAL-24] - What should be done when multiple META-INF/validation.xml are found?
    * [BVAL-117] - Specify behaviour of ConstraintValidator.initalize in the case of inconsistent values in constraint parameters
    * [BVAL-127] - Remove ConstraintViolation.getGroups()
    * [BVAL-128] - Clarify invalid cases for validateProperty / validateValue on proeprtyName being empty or null
    * [BVAL-133] - Remove JPA and JSF integration proposals




1.0.Beta2 Public Draft (2008-12-15)
-----------------------------------


** Bug
    * [BVAL-6] - Wrong example in validation methods section
    * [BVAL-17] - Validator<A>.validate(b) where b:B and B extends A should validate B. Metadata APIs are specific to A
    * [BVAL-42] - Names of message keys in spec inconsistent
    * [BVAL-45] - Typo at ConstraintDescriptor.getContstraintClass()


** Improvement
    * [BVAL-29] - Types should be determined at runtime
    * [BVAL-33] - Should ConstraintDescriptor.getConstraintImplementation() replaced by .getConstraintImplementationClass()?
    * [BVAL-40] - Rename InvalidConstraint to ConstraintViolation
    * [BVAL-48] - Add a way to access the default message resolver
    * [BVAL-49] - Mark metadata classes as immutable
    * [BVAL-59] - Rethink the group sequence inheritance rules
    * [BVAL-60] - ConstraintViolation points to the corresponding ConstraintDescriptor
    * [BVAL-68] - Specify that static methods and fields are not validated
    * [BVAL-73] - Rename ConstraintViolation.getBeanClass() to CV. getRootClass() or simply remove it
    * [BVAL-78] - Forbid a Validation implementation to modify the state of the object being validated

** New Feature
    * [BVAL-30] - Define validation Context to be passed to constraint implementation calls
    * [BVAL-36] - Validation of method parameters and returned values
    * [BVAL-67] - Allow MessageResolver to be Localizable
    * [BVAL-71] - Should we have group aggregation?
    * [BVAL-76] - Expose the raw message to ConstraintViolation
    * [BVAL-79] - Groups are now Type based rather than String based
    * [BVAL-81] - Provide a TraversableResolver contract


** Task
    * [BVAL-1] - Remove references to 'beancheck' in the spec
    * [BVAL-3] - Replace array return types with Sets
    * [BVAL-4] - Return value for @NotEmpty for null values
    * [BVAL-5] - Change order of exmaple classes in Book/Author example
    * [BVAL-7] - Use of example in ConstraintFactory section (2.4)
    * [BVAL-8] - StandardConstraint description (2.5)
    * [BVAL-23] - Make Validator<T> thread-safe