Toplink insert new value issues

Question

Hi all,
I'm working on toplink and encounter a problem.
I have 3 tables, A(a.id), B(b.id) and relation table AB(a.id(fk),b.id(fk)),
Now table B have one value(b1)(b1 got from sessionBean.findByid method ),
I want to add a new value A(a1) to database, and the relation table AB(a1,b1)
So I have the following code.
A a = new A();
List listAB= new ArrayList();
AB ab = new AB();
ab.SetB(b1);
listAB.add(ab);
a.setAB(ab);
sessionBean.persisA(A)
But the toplink persis B(b1) once again.
So there is an error,because b1 already exists in Database.
Anyone have solution for this problem.
Thanks.

Answer 1

The problem is in what sessionBean.persisA(a) does, and what the sessionBean.findByid does - is it just a register object? Also, you describe the A->B table relationship as a Many to Many using an AB as the relation table, but in the objects you seem to create an AB object for the relation table. Is there a reason A just isn't using a collection of Bs with a ManyToManyMapping specifying AB as the relation table? In the code description, you also state a.setAB(ab); which I assume was just a mistake and that the problem really uses a.setAB(listAB), but just to be sure, what do the ab.setB() and a.setAB() methods do, and how is the AB->A value set?
Best Regards,
Chris