Replace collection [TOPLINK-4002] error

Question

Hi all!
I've a 1:N relationship.
I need to replace the objects in the collection.
I've used the following code:
if (distretti != null) {
//create new list
usrlgdistretti=new ArrayList(distretti.size());
it = distretti.iterator();
//add elements to list
while (it.hasNext()) {
Tbdistretti dist=(Tbdistretti)unofw.registerObject(it.next());
if(dist!=null){
Usrlgdistretti uld=(Usrlgdistretti)unofw.registerObject(new Usrlgdistretti());
uld.setDistretti(dist);
uld.setTdbuser(user);
usrlgdistretti.add(uld);
//change the collection
user.setUsrlgdistrettiCollection(usrlgdistretti);
but, if I try to replace the collection [object A, object B] with the collection [object B, object C], i get an [TOPLINK-4002] error, caused by object B and the UNIQUE constraint.
do I need to use "performDeleteFirst" of unitofwork?
can you please help me?
thanks!

Answer 1

Replacing the collection is fine. The rule of thumb though is that the objects in the new collection should be working copies retrieved from the database and registered with the UnitOfWork. If ObjectB was an existing working copy you would not see and INSERT attempted for it.
Instead of simply creating new instances for the target collection you need to see if you can retrieve existing elements to use.
Doug