MySQL: How do you get the next auto_incremented number when merging? If I set it to the correct value it works but how are you supposed to know which number that is? I get exceptions when trying to merge objects which have the auto_incremented primary key set to null. I don't want to set it. I want it to be auto_incremented. Do I change the database or is there something you can do in the Hibernate JPA code?

Is it impossible? Not even with native queries? I create a new object which I want to persist in the database. The id is auto_incremented.

You might have misunderstood the meaning and usage of "session.merge()" method. It's used to MODIFY a persisted object. That's mean, the object you are merging with should already be loaded in previous session and it is detached mode, in another word, it should already have an existing ID value for this object at this point, and no new value is generated during merge().

Your identity ID property(MySQL auto_increment in your case) is used when you go persist a new object. And if you map this right, it should be auto generated for you and you may retrieve it after object is persisted.

See http://docs.jboss.org/hibernate/stable/ ... e-detached

I got it to work. I changed the database table definition some and loaded the new auto_incremented object with a find after merging it.
KEY `TEST_ID_KEY` USING BTREE