Early on in the Open For Business project we used a code generator to create CMP entity beans, deployment descriptors, delegates and so forth, even JSPs and events or actions to update the data.
The tool was knows as EntityGen because it generated the code based on definitions of entities which corresponded to relational tables.
That is still available if you want to use it (get the 2001.07.20 release), but it has been deprecated. In the most recent release of OFBiz we have evolved the entity code generator into a dynamic entity engine. This uses the data transfer hashmap pattern and enforces rules about the data from entity definitions in an XML file. In addition these entity definitions are sufficient to do things like automatically creating tables or columns in the database and handling all of the persistence of these generic, dynamic entities.
If you are doing a lot of persistence work one of these might be useful. If the work is very procedural, entity definitions probably won't help you. Just use your favorite J2EE IDE (Forte from Sun, for instance) to automatically create stubs from interface definitions.
Best of luck,
David E. Jones
The Open For Business Project
jonesde at ofbiz dot org