I have a situation in which I have a many-to-many relation split up in two one-to-many relations using a join table. Normally, each id of the join table referes to some unique entity. For example; Blog - BlogUser - User
After setting up the relations in Blog and User, you can ask a Blog for its collection of users, and inverse, you can ask a User for its Blogs.

Now, my problem is a bit more complex. I have don't have 'unique' entities, in fact, the link table maps id's of the same table.

So I have; User - UserEquality - User

The goal that UserEquality denodes the id's of users which are 'equal'.
Imagine I have three users:



All three acutally represent the same user.
The linktable would then have these entries:



I could map two "one to many" relations in "User" each on a different id. So I would have :

User.hbm.xml


This is all good, I have two relations on the same entity.

Now, with this setup I want to lookup the users that are equal to "Geraald". The problem is that I need a union of both relations. Retrieving "userEqualityA" is only half of the solution ; I only get "Gerold" back.

The thing is, with blog and users you have a clearly defined relation between them. Asking a blog for its users always returns the complete story for that relation; you get what you asked for; all the users registered for that blog. Also, if you ask a user for its blogs; you get what you asked for; all the blogs on which this user has registered.

With this user equality all sides of the relation are 'equal' , there is no pre-defined order. So the correct answer on "give me the equal users" would be a "joined" collection of both the userEqualityA and userEqualityB relation.

So, I'm looking for a way in hibernate to return a 'joined' collection of both userEqualityA and userEqualityB. I don't want to map these relations to my entity objects, since the user would be a ble to only use one of them (and thats not correct; you always need both relations to have a correct view of equal users)[/code]