I have a database structure that models a forest of trees in a single table.
This is achieved by the table having 3 fields, the primary key, the primary key of its parent item (pointing to the same table), and a field to identify which tree in the forest this node belongs to.

Due to performance issues, I am not referencing the 'parent' or 'child' elements as 'classes', but just as strings of the promary keys.
So the children collection would be a collection of PK strings, rather than the class objects themselves.

My issue is that the only way I can model this in a class is to have a Map of Sets of strings.
This would work perfectly, if I had tree1, tree2, and tree3, then

myobject.children['tree1'] woud be a Set of strings identifying the PKs of each child element.

Any idea how I would model this in an HBM?
I dont think its possible to place a <set> inside of a <map>...

Any ideas?

Thanks in advance.

- Adam Langley

why dont you just use lazy=true on the classes ?

doing obj.getId() doesnt initialize a object so you wouldnt have any memory hit and you can work with objects instead of their string identity.

Ah, I cant use lazy on the objects because I have to pass the object over web services, so I just want a localized portion of the tree,

ie, this node + parent IDs / child IDs
(its actually a MAP, not a TREE, which is why theres multiple parents...)

sounds like you should think of separating your "biz" object model from your "presentation" (the webservice objects)