What happens if I map a bidirection association, and don't mark either end as inverse? Here's my scenario:

I have a Contact and a ContactGroup managed objects. A ContactGroup can have many contacts, and each contact can be in many groups. So I've mapped a <many-to-many> association on both ends.

The end user will be able to edit this association from both ends: he can either edit a group, and than add users to it, or edit an user, and add groups to it. What I really want is be able to do both:

contact.getGroups().add(someGroup);

OR

group.getContacts().add(someContact);

And have either of those statements update the relationship table at flush time. In other words, I don't want to bother about which end manages the association -- I want both ends to do it. It seems to work right now, but I'm not sure of the consequences. Any words about this?

If you add to both ends, you will get a uniqueness constraint violation (or the row will be inserted twice if you don't have a constraint).

Hmm, if this is the only problem, I guess I'll leave the relationship mapped this way. The way the application works, I'll never modify both ends of the relationship in the same transaction.

I do something similar so that delete-orphan cascades work from both ends of a many-to-many. I haven't found any serious problem with it.

However, for your situation, you'd be better advised writing some addXXX helper methods that automatically set up both ends of the association:

class Bar:

public void addFoo(Foo foo)
{
foos.add(foo);
foo.getBars().add(this);
}

Thanks, Nebob. I'll consider adding something like this.