Enterprise JavaBeans 3.0 (EJB 3.0) is a vital component of the new Java Enterprise Edition 5 platform (previously called J2EE). They are used for the development and deployment of component-based enterprise business applications. Ever since its first release, EJB has been the subject of much media attention and no little controversy. EJBs represent a sophisticated and powerful technology and EJB-based applications can support high numbers of transactions and users, with maximum security. However, previous incarnations of EJB have come to be regarded by many as an overly complex technology that can lead to costly and time-consuming solutions that are difficult to build, implement and maintain. EJB 3 is set to change all that. It has made huge advances in ease of development, and its drastically simplified programming model has been widely acclaimed and embraced. At the heart of the new EJB 3 spec is a massive reduction in the complexity of the EJB persistence and object-relational mapping mechanisms (essentially the entity beans portion of the specification). This book provides the definitive guide to the EJB 3 persistence technology.