Hibernate is an open-source project that handles the role of the persistence layer, becoming the middleman between the business logic code and the database data. Its expressed purpose is to free developers from the tedious and common coding of database tasks such as queries, insertions and deletions.
Take the previous DAOExercise as an example, where most of the code dealt with inserting, selecting and deleting data from the MySQL database. Hibernate would handle these mundane tasks and allow the developer to focus more on the business logic and rare SQL code exceptions.
HIbernate incorporates ORM (object/relational mapping), which will map objects to their proper tables in the database. Such logic would be used when hand-coding DAOs using raw JDBC, and it would be up to the developer to track and maintain any changes in either object or database table. Use of Hibernate simplifies matters and make maintenance easier.