I have the following situation: I have loaded an object of class A (A0), which has several children of class B (B0 and B1), and closed the session in which that happened. In a new session, I now load A1, with children B0 and B2. There are now two different instances of object B0, while I would like there to be just one. Is it possible to do this with Hibernate?

thanks,

Jeroen

Once you detach the domain objects from Hibernate, Hibernate has no way of knowing about them. The only way to accomplish what you are trying to do is by reattaching A0 to the new session (with session.lock), with cascade="lock" (or equivalent) on the B collection. Then, when you load A1, the first level cache should return the cached B0 entity (afaik).