The incremental database reverse engineering (DBRE) add-on allows you to create an application tier of JPA 2.0 entities based on the tables in your database. DBRE will also incrementally maintain your application tier if you add or remove tables and columns.
M. Granitzer, W. Kienreich, V. Sabol, and G. Dosinger. Proc. Twelfth IEEE International Workshops on Enabling Technologies:
Infrastructure for Collaborative Enterprises WET ICE 2003, page 296--301. (2003)