[bv-dev] BVAL-234 @NotNull @Id for JPA and Bean Validation

[Hardy Ferentschik]

Is option #3 even possible within the JPA spec? One would need meta information about the id property 
(which generation type and how exactly this type behaves regarding the id generation time). I don't think there
is a way to do this with the JPA api. Also  JPA does not even explicitly define the behavior of the different strategies. 

Disabling the validation per default can also backfire in the cases where a user "knows" that a certain strategy 
will generate the id pre insert. In this case it would be valid to add @NotNull.

To me option #1 sounds best. Maybe #2, but I am not convinced that it is needed.

--Hardy

On May 15, 2012, at 10:22 AM, Emmanuel Bernard wrote:

> There is an annoyance when using JPA and Bean Validation today. I worked out a proposal. Please let me know what you think
> 
> http://beanvalidation.org/proposals/BVAL-234/
> 
> --- (copied here for convenience) ---
> 
> [Link to JIRA ticket][jira]  
> See also [NetBeans issue][netbeans]
> 
> ## 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.
> 
> ## Solutions
> 
> ### 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 User adjusts with some help
> 
> We could use option 1 but have JPA provide the created group: `javax.persistence.validation.groups.Created`
> 
> ### 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.
> 
> ### 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.
> 
> ### Questions remaining
> 
> - should the `Created` groups be renamed?
> - is that correct to sneakily disable @NotNull constraint validation?
> 
> 
> [netbeans]: http://netbeans.org/bugzilla/show_bug.cgi?id=197845#c3
> [jira]: https://hibernate.onjira.com/browse/BVAL-234
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