FYI, I have always thought that the DefaultTreeModel makes it difficult to efficiently load a TreeModel from the database. If you're not careful, you will fire N+1 selects.
I have created an (untested) LazyTreeModel which IMO is much easier to implement an efficient database lookup for tree nodes. The LazyTreeModelAdapter is a much more database friendly interface which logically separates the calls. Code here https://gist.github.com/uklance/5795703 BE WARNED: It's untested
