Make TABLE-generated IDs available on PrePersist

[lukasj]

JSR-338/3.5.3 states that

Generated primary key values are available in the PostPersist method.

It'll be much helpful if those ids whose strategy is GenerationType.TABLE are available on PrePersist.

exempli gratia

public class MyEntity {

    @PrePersist
    private void onPrePersist() {
        // generate a unique and unchangable value from *available* id.
        derived = String.format("%1$016x", id);
    }

    @GeneratedValue(..., strategy = GenerationType.TABLE)
    @Id
    private Long id;

    @Basic(optional = false)
    @Colum(..., nullable = false, updatable = false)
    @NotNull
    private String derived;
}

Note that the derived column is not null and not updatable.

[lukasj]

@glassfishrobot Commented
Reported by jinahya

[lukasj]

@glassfishrobot Commented
neilstockton said:
FWIW DataNucleus JPA already does set ids from all non-IDENTITY value generators (i.e TABLE, SEQUENCE, custom) prior to PrePersist, so hence the values are available in that method.

[lukasj]

@glassfishrobot Commented
This issue was imported from java.net JIRA JPA_SPEC-133

[lukasj]

• Issue Imported From: https://github.com/javaee/jpa-spec/issues/133
• Original Issue Raised By:@glassfishrobot
• Original Issue Assigned To: @ldemichiel

[gavinking]

This is a pretty reasonable and useful request, it seems to me, and to be honest I'm not sure why Hibernate didn't already do things this way (I guess nobody ever asked us directly). But anyway, looks like I've been able to get that working with a very straightforward change. So from our side I don't think we would have a problem adding it to the spec.

@lukasj WDYT? What does EclipseLink do here?

[gavinking]

I have proposed #488. Let's see if other implementors object.

[lukasj]

EclipseLink already supports this

[gavinking]

OK, so I checked with the Hibernate team and they do not object to the change.