Middlegen with Hibernate: it will ease the job to generate the mappings from a legacy database. On Middlegen site you can see:
database-driven code generation engine
So, instead of writting by hand some tens/hundreds of mappings you just get from Middlegen at least a draft for 'em.
Middlegen uses
JDBC to connect to the DB (so it is easy to be configured) and then for code generation: Velocity and XDoclet.
./pope