Bean Validation

Fix annoyance between JPA and Bean Validation when @Id @GeneratedValue and @NotNull are used

1. Problem description

Today when a property marked @Id @GeneratedValue is also marked @NotNull, it will fail if the identity generation is post-insert in the database. This can be the case if the underlying table is using column id generation for example.

The id property is thus null when Bean Validation is executed during the pre-persist phase and a constraint violation is raised.

2. Solutions

2.1. 1. User adjusts

One option is to stay put and consider the behavior valid. The user can work around that by:

  • creating a com.acme.groups.Created group

  • marking the @NotNull annotation as belonging to the group

  • override the groups in persistence.xml to validate Created accordingly

Here is the snipped of the persistence.xml file

<property name="javax.persistence.validation.group.pre-persist"
          value="javax.validation.groups.Default"/>
<property name="javax.persistence.validation.group.pre-update"
          value="javax.validation.groups.Default,com.acme.groups.Created"/>

2.2. 2 User adjusts with some help

We could use option 1 but have JPA provide the created group: javax.persistence.validation.groups.Created

2.3. 3. Have JPA disable validation of id properties at pre-persist

JPA could disable validation on id properties if in pre-persist and if the generated value is not created yet. Note that we disable all validations - not simply @NotNull - as it does not make much sense to execute other validations when a property is null.

TraversableResolver can be used to solve the problem as isReachable can stop the processing of a property.

2.4. Conclusions

Option 3 seems the most reasonable but it could be complicated at the JPA level. Before going to the JPA EG, let’s discuss the situation here.

2.5. Questions remaining

  • should the Created groups be renamed?

  • is that correct to sneakily disable @NotNull constraint validation?

  • could we as JPA to validate the object id property once the id has been set (flush time in this case)?