I have a detached instance a, of which another instance b with the same id might already be loaded into the persistent context.

The state of a should be updated into the database, so I call
entityManager.merge(a);

If a still exists in the database, this performs well: I get an optimistic lock exception if a has been modified meanwhile.

If a has been deleted in the database meanwhile, I 'd like to get an exception too, but instead it insert it as a new record.
How can I get an exception instead?

Please note that I have no idea if there is a b with the same id or not already in the persistent context, so I can't check if b throws a optimistic lock exception.

Thanks for any and all help :)

Just load the object by id. You'll get an exception or a null result depending on the method used.

Thanks, that works :)

But won't that hurt my performance?
I iterate through a list of P's, on which I load and merge continually, so I get a select-update-select-update-... pattern,
while I'd like to get:

update/delete ... where p.id = :id and p.version = version
If that changes 0 records it should trow an optimistic locking exception.
Notice I never want merge to insert something.

Ok, so how about this;


check with contains(), if the object is contained in the session.

If so do a merge(), else do an update().

I have not tried this, but I'd say it might work.

That doesn't work, because contains() returns false, even if a persistent instance with the same id is already in the cache.
That means that it still crashes once you run update because there is already a persistence instance with the same id in the cache.

Hmm I don't understand the problem with the cache (I asume you are referring to the second level cache?)

Can you post some example code and the exception you get?

Hmm I don't understand the problem with the cache (I asume you are referring to the second level cache?)

Can you post some example code and the exception you get?

Actually I mean the first level cache.

Try something like this:

P detached = em.get(P.class, 101);
em.clear(); // detach it
detached.setDescription("dirty");

em.get(P.class, 101); // Load another instance with the same id in first level cache
if (em.constains(detached)) { // returns false
// this code isn't executed
}
em.getDelegate().update(detached); // throws exception because another instance with the same id is already in the first level cache.



Note I don't want to do em.clear(), because that causes havoc when I am building graph tree.

Ok, now I get it.

I don't know about the entitymanager, but I guess you can get the underlying Hibernate session.

now try this:




This assumes, that getId() returns the id of your detached object.

You might have to activate statistics first, and I don't know what that does to your performance ...

If this doesn't work you could still try to hack your way in the Session private fields and methods ... after all they have to have the Ids somewhere ...