Dear all,

When I persist an entity I need to know a unique id for it before commiting the transaction. As stated in another thread, the id of an entity can only be obtained via getId() after commiting – at least if you want your code to be portable.

In order to overcome this, I want to add another field to my entity, getReference(), say, which stores an id which I manually set before calling session.save(). For this, I need a way to generate unique id's and I thought, I could use one of Hibernate's generators. How could I do this?

I need something like

UniqueIdSource.getNext()

which returns a new id each time it is called; for instance, it increments the current value and returns it. It should be synchronized and persist the id.

Can somebody give me a pointer on which Hibernate generator I could use for this and how?

It is important that UniqueIdSource.getNext() runs in its "own" transaction – not that two concurrently running sessions obtain the same id because neither of them has committed yet.

Thanks,
hbf

P.S. I am using Hibernate with Spring and a single data source.

Hmmm... I don't think this is entirely true. If you use session.save() to save your object it will return the id that has been assigned to that object. The thread you are referring to are discussing session.persist() which works differently. It doesn't return the id, and thus id generation can be delayed until later. In the "worst" case, until commit().

You are right! – My mistake. save() returns the id!

Apologies,
Hbf