Hibernate version: 2.1.6

I have objects A and B, connected by a many-to-many relationship A_B. I'm using a Swing GUI to manipulate data, i.e. load an object of type A including the relationship to B, display in the GUI, and then allow the user to add and delete relationship objects A_B from the loaded object A. Because of the Swing GUI I am not keeping the sessions open, but rather open and close only when directly interacting with the DB.

Here is what I currently do when adding:
- create a new instance of A_B
- add the corresponding object A and object B to the new instance of A_B
- open a session
- save new instance of A_B
- close the session
- open a session
- refresh the object A (session.refresh) and reload the collection of A_B relationships
- close session
- update GUI, so that the new A_B instance is also displayed as part of the collection of A

What I tried and didn't work:
- after saving the new instance of A_B, "manually" add A_B to the collection in A. When I do this, I will get problems later when continuing to work with A (the problem is when I try to do a session.lock(A, LockMode.NONE) to reattach the object to the session, Hibernate complains about "dirty collection").

Questions:
- what is the proper way to add or delete an object A_B related to A, particularly do I have to "manually" add the new A_B instance to the collection (in my case a Set) managed by A (but without provoking "dirty collection" exceptions later)?
- is there a proper way to reload / re-initialize a collection from the database (just the collection, not the whole object which contains the collection)? In my case the object A might be loaded with several related collections, so doing a full refresh might be rather costly, which is why I'm not really happy with the refresh-approach outlined above.


thanks in advance
Peter

bumping the thread, hoping to get some input...

It depends on how these are mapped bi-directional and whether they are cached. The safest bet is to update all sides of the assocations you have defined to Hibernate. Typically this would mean something like:



or more succintly from client perspective:



Specifically, this should be done before saving the new instance of A_B...

Thanks for the feedback!



So the question boils down to: which objects do I have to save / update after having done the adds. When I only insert ab (the new A_B object), then I will get later the "dirty collection" exception. However, when I update a and b, then even though no attributes have changed for these rows, they will get an incremented version or timestamp, which is a problem for me. Am I doing something wrong?