Enterprise JavaBeans 3.0, 5th Edition

Chapter 2. Architectural Overview

To use Enterprise JavaBeans and Java Persistence effectively, you need to understand their architectures. This chapter explores the core of the EJB and Java Persistence architectures: how enterprise beans are distributed as business objects and how they interact with Java Persistence. Chapter 3 explores the services and resource-management techniques supported by EJB.

In order to be truly versatile, the EJB component design had to be smart. For application developers, assembling enterprise beans requires little or no expertise in the complex system-level issues that often plague three-tier development efforts. While EJB makes the process easier for application developers, it also provides EJB server developers with a great deal of flexibility in how they support the EJB specification.

Java Persistence also makes it fairly easy for developers to write objects that can be persisted to a relational database. Writing a persistent entity bean can be as easy as using a few strategically placed annotations with little to no information about the database. Although it is easy to prototype entity beans, the specification is rich enough to provide facilities for more complex database mappings.

The Entity Bean

Entity beans in the Java Persistence 1.0 specification are available only as plain old Java objects (POJOs), and are mapped to tables in a relational database. Unlike other EJB types, entities can be allocated, serialized, and sent across the network like ...