Hibernate, created by Gavin King, known as the best and dominated object/relational persistence (ORM) tool for Java developers (Now is support .NET). It provides many elegant and innovative ways to simplifies the relational database handling task in Java.
Hibernate is great at a lot of things, but its something that needs to be used appropriately. In this tutorials, it providing many step by step examples and explanations on using Hibernate4
Hibernate 2 Quick Start
Primary Key in Hibernate
Collections in Hibernate
Inheritance in Hibernate
Table per Subclass Using Annotation
Table per Concrete class Using Annotation