Hi, I have need for bidirectional many-to-many. The doc says one end must be inverse=true, but I need to manipulate from either end. How do I do that?

From the spec:

"You may map a bidirectional one-to-many association by mapping a one-to-many association to the same table
column(s) as a many-to-one association and declaring the many-valued end inverse="true"."

OK - so the same appears to be true for one-to-many as well. Doesn't inverse=true imply that the relation can be maintained/persisted from only one end. But I need to maintain/persist from both ends.

My question applies to both <many-to-many> and <one-to-many>

Heeeelp!

You can manipulate relationship both side if you use inverse="true". butw hen you add a object from one side, you must add on the otjer side

a.getBs().add(b);
b.getAs().add(a);

This is the expected behavior in Java.

Not setting inverse="true" will try to insert the relationship twice.

Thanks. But what is the behaviour if both sides have inverse=false?

I'm inclined to skip the entire inverse=x thing, cus' it confuses me. Are there instances where I MUST use inverse=true?

Of course. Actually, it is used behind the scenes to determine the order of SQL statements sent to the database. It is required to prevent foreign key constraint violations, like with a child (FK to parent) inserted before the parent.

Try to understand it, you can't do without.

Thanks Christian and other. My problem is that I try to automatically map from a UML model (having associations with muliplicity and navigability).

But there is inverse=x notion in UML, so I don't understand how to make this automatic :-(

UML is a language. It has nothing, repeat with me, nothing to do with object models and database schemas.

So for bidirectional many-to-many, does it matter what side is inverse? Or will any side do?

Do you understand my problem? My task is to generate mapping from UML diagram (rational rose)

For a bidirectional many-to-many association, can I put inverse=true on either side?

Thanks.

No, it does not matter if in your code, you do what I did (set both side)

OK, then. So, given my Rational Rose model, it sound like this plan will work:

For bi-directional many-to-many relations, set inverse=true on one end - which one doesn't matter.

For bi-directional one-to-many, set the many-side inverse=true.

Sounds OK? Any caveats?