jtree and sql queries

Hi all,
I'm just wondering if someone has already bound a JTree to a set of sql
queries. I explain it better: I've got a person table, a skill table and a
role table. Each person can play one or more role, and can have one or more
skill. I'd like to show to the user the result of the query as a tree:
person
+- roles
+- role1
+- role2
+skills
+- skill1
+- skill2
....

As you can imagine, the difficult is to bind each node tree to its table and
to a specific query. For now I've bound each node to its table and its key
value (with bound I mean that from the node I can know which table and key I
must use to find the row in the database), but my difficult now is to refresh
the tree each time the user makes a changes to the database. Unlike the use
of simple tables, building the tree is more complex, because more queries
must be performed, so I was wondering if someone out there has already
something similar and can suggest me.

Thanks,
Luca