Problem with toplink persistEntity method

Question

Hi,
i have a problem.
I have two tables. One is master and the second is dependent on the first (reationship 1:N)
I have jspx page with master table and this dependent table and everything works fine. Except two errors. I cannot add anything twice to the dependent table. When i call create method from bindings for the first time, new row is inserted, i fill the attributes, call merge entity, and everything is done correctly (old records are updated and the new one is inserted). But when i do it again, i got an Exception :
javax.faces.el.EvaluationException: javax.ejb.EJBException: Exception [TOPLINK-7197] (Oracle TopLink - 10g Release 3 (10.1.3.0.0) (Build 060118)): oracle.toplink.exceptions.ValidationException
Popis v�jimky: Exception in changes determination. Primary key cannot be null.; nested exception is: V�jimka [TOPLINK-7197] (Oracle TopLink - 10g Release 3 (10.1.3.0.0) (Build 060118)): oracle.toplink.exceptions.ValidationException
description: . Primary key cannot be null.
It looks like JDeveloper calls update instead of insert although it is a new record. Because in database is a trigger that works on insert a row and fills primary key automaticcaly from sequence. So, what is wrong ? Why the first call works, but the second dont ?
The second problem is, when i create a new row in master table, and also new row in dependent table, i dont have primary key to fill in dependent table yet. And when insert is called, it throws same exception as above. I use collection attribute to hold reference on records in dependent table. Must i have call persist entity on main object without collection of dependent objects and then ,after i receive primary key, call persist entity on that collection ?
i use JDeveloper 10.1.3.0.4 (SU5)
thanks for help

Answer 1

I have found what cause this problem.
After persisting a new object the Id is not returned and is not wrote into POJO object. And then the next update tries to update a record that has null in a primary key field.This results in an exception mentioned above.
This is why it works for the first time (the objects that exist are updated, objects that do not exist are inserted into database-but the id is not written in POJO because it is generated by sequence in database and toplink dont update object with it). This result in a object that have no Id, thus next try to update him throws "primary key is null" exception.
I hope this will help a lot to understand what is the problem.
I found a method in UnitOfWork that says:
A valid changeSet, with sequencenumbers can be collected from the UnitOfWork After the commit is complete by calling unitOfWork.getUnitOfWorkChangeSet()
but i havent found the new sequence number in it:(.
Does anyone can help how to solve this ? How to get the id?
I must say that toplink is more and more disappointing for me :(.