Works as List, not as Map

Question

I'm having an issue with 1-M mappings where the type of the child attribute is a java.util.Map. When I read the parent and reference the child, Toplink is only populating one object in the Map, even though there multiple in the database.
When I change the data type on the collection attribute to a List, all children are correctly read - i.e., it works fine.
In the collections tab in the workbench, I set the collection type to IndirectMap when using a Map (and set the key method appropriately), and Indirect List when using a List.
In debug (JDeveloper) when processing as a Map, I do see the key method accessed, and actually see data from all children in the debugger data view as it cycles through them. However, only the last object (which it seems to cycle through twice in the key method) ends up in the map. Unfortuntely, the debugger doesn't let me see what's happening with the population of the collection.
This happens whether I use indirection (transparent or value holder) or not.
Any idea on what I'm missing? Code snippets below (parent is Firm, child is FirmOfficer - there are 3 on the database; intent is to read/update all children):
List code:
Firm firm = (Firm)session.readObject(Firm.class);
UnitOfWork uow = session.acquireUnitOfWork();
Firm tempFirm = (Firm)uow.registerObject(firm);
tempFirm.setState("CA");
List l = tempFirm.getFirmOfficers();
// size() of list is 3
Iterator i = l.iterator();
FirmOfficer fo;
while (i.hasNext()){
fo = (FirmOfficer)i.next();
fo.setState("CA");
uow.commit(); //all 3 children updated
Map code:
Firm firm = (Firm)session.readObject(Firm.class);
UnitOfWork uow = session.acquireUnitOfWork();
Firm tempFirm = (Firm)uow.registerObject(firm);
tempFirm.setState("CA");
Map m = tempFirm.getFirmOfficers();
//size() of map = 1
Set s = h.keySet();
Iterator i = s.iterator();
FirmOfficer fo;
while (i.hasNext()){
fo = (FirmOfficer)h.get(i.next());
fo.setState("CA");
uow.commit(); //only the 1 child is updated
Thank you.

Answer 1

Check that the value you are using for the Map key is unique. i.e. each object in the collection must have a unique key value otherwise with a Map you will only end up with a single element if they all share the same Map key.