Hi all..

I am having a strange problem with my many-to-many association.

I have an object 'A' assocaited with object 'B' through object 'AB.'
AB has additional fields, so I have done the mapping as a composite element with a 'many-to-one' element within it.

The strange thing that I have noticed, however, is that when I load Object 'A' and do a trivial operation on the collection (say, for example, A.getB().size()) it works fine, but when the session commits, it deletes all of the associations, and re-inserts them. In fact, it deletes each of my association elements 1 by 1, and then reinserts them...

any ideas?

thanks,

joe

Okay... so I implemented equals() and hashcode() on my composite element and it seems to have solved the problem... and created a few more questions.

Can someone explain, or point me to a document that explains, why this is necessary? Is it because the composite-element is not a full fleged persistant object, and thus Hibernate does not track it's identity?

Also my class, 'AB' does not have any of the foreign key fields in it. The only fields it has is a property object (in my case a boolean) and a field for 'B' (for the many-to-one). Thus when I implement equals() and hashcode() I only have these two fields to work with. It seems to work, but it doesn't feel like it's the proper thing to do. Should I make sure this composite-element also contains a field that holds the id of it's parent?
(thus, really implementing the databases's idea of identity?)

thanks!

joe

http://www.hibernate.org/109.html is a good material
and the reference guide too.

No, it is because of the semantics of java.util.Set