New System
For the tasks that do not use neither an existing Java layer, nor an existing database schema, Cayenne mapping project can serve as a starting point for both. User would start a new Cayenne project, create a DataMap with DbEntities corresponding to the desired schema, and then create a set of ObjEntities on top of that. After this is done, both Java and database layer can be generated from the mapping.
See the following topics explaining individual tasks involved: