Manually specify the value of a primary key in JPA @GeneratedValue column

Question

I\'m having an Entity which has a primary key / id field like the following:

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


        

Answer 1

If you use TABLE sequencing, then EclipseLink will allow you to override the value (or SEQUENCE if your database supports this, MySQL does not).

For IDENTITY, I'm not even sure that MySQL will allow you to supply your own Id, you might want to verify this. In general I would never recommend using IDENTITY as it does not support preallocation.

There are a few issues with allowing IDENTITY to provide the id or not. One is that two different insert SQL will need to be generated depending on the id value, as for IDENTITY the id cannot be in the insert at all. You may wish to log a bug to have IDENTITY support user provided ids.

You should still be able to get it working with your own Sequence subclass, or possibly MySQLPlatform subclass. You would set your MySQLPlatform subclass using the "eclipselink.target-database" persistence unit property.