Hibernate is a free, open source Java package that makes it easy to work with relational databases. Hibernate makes it seem as if your database contains plain Java objects like you use every day, without having to worry about how to get them out of (or back into) mysterious database tables. It liberates you to focus on the objects and features of your application, without having to worry about how to store them or find them later
Working with Hibernate is very easy and developers enjoy using the APIs and the query language. Even creating mapping metadata is not an overly complex task once you’ve mastered the basics. Hibernate Tools makes working with Hibernate or EJB 3.0 persistence even more pleasant.