Simplifying EJB Development with EJB 3.0

Enterprise JavaBeans (EJB) has been criticized by many developers for its complexity. EJB 3.0, being worked under JSR-220 of the Java Community Process, is designed to simplify development of applications and standardize the persistence API for the Java platform.

In this article, I will explain how EJB 3.0, a full implementation of which is available in Oracle Application Server EJB 3.0 Preview, simplifies the programming model for EJB and defines a simple API for persistence.

Complexities with EJB 2.x

The current EJB 2.x model is overly complex for a variety of reasons:

• The current EJB model requires you to create several component interfaces and implement several unnecessary callback methods.
• The component interfaces require implementation of EJBObject or EJBLocalObject and handling of many unnecessary exceptions.
• The EJB deployment descriptor is complex and error prone.
• The container-managed persistence, being based on the EJB model, is overly complex to develop and manage. Several basic features are missing--such as a standard way to define a primary key using a database sequence. The EJBQL syntax is very limited.
• EJB components are not truly object-oriented, as they have restrictions for using inheritance and polymorphism.
• Developers cannot test EJB modules outside an EJB container and debugging an EJB inside the container is a nightmare.
• Looking up and invoking an EJB is a complex task. Detailed knowledge of JNDI is required for even the most basic use of an EJB in your application.

Simplifying Developers view

If you’ve ever developed an EJB with the current spec, you probably realize how difficult it is develop a simple EJB such as HelloWorld EJB. Even for this simple task, you need at least two interfaces: a bean class and a deployment descriptor. IDEs such as Oracle JDeveloper and utilities like XDoclet simplify these mundane tasks; however, it is still the responsibility of developers to compile these classes and package the deployment descriptor before the EJB can be deployed in the container of choice.

EJB 3.0 is designed to address the complexities of the current EJB model by:

• Removing need for unnecessary interfaces and implementation of callback methods
• Using metadata annotations instead of deployment descriptors
• Using regular Java classes as EJBs and regular business interfaces for EJBs

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