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EJB 3.0

What is new in EJB 3.0?

Now, have a look over the new features of EJB 3.0 that achieved some simplicity over the previous EJB APIs in various ways:

1. EJBs are now Plain Old Java Objects (POJOs)

2. No need of home and object interface.

3. No need of any component interface.

4. Unnecessary artifacts and lifecycle methods are optional

5. Use of java annotations instead of using XML descriptors

6. Use of dependency injection to simplify client view

7. Simplify APIs to make flexible for bean’s environment

8. Defaults are assumed whenever possible

Types of EJB

There are three different types of EJB that are suited to different purposes:

• Session EJB—A Session EJB is useful for mapping business process flow (or equivalent application concepts). Session EJBs commonly represent “pure”
functionality that is created, as it is
needed.

 

Entity EJB—An Entity EJB maps a combination of data (or equivalent application concept) and associated
functionality. Entity EJBs are usually based on an underlying data store and will be created based on that data within it.

• Message-driven EJB—A Messagedriven EJB is very similar in concept to a Session EJB, but is only activated when an asynchronous message arrives.

Session Bean on EJB Container

Session beans are divided into two parts.

Stateless: A session bean is the enterprise bean that directly interacts with the user and contains the business logic of the enterprise application. A session bean represents a single client accessing the enterprise application deployed on the server by invoking its method. An application may contain multiple sessions depending upon the number of users accessing to the application.

Stateful: These types of beans use the instance variables that allow the data persistent across method invocation because the instance variables allow persistence of data across method invocation. The client sets the data to these variables, which he wants to
persist. Stateful session beans have the extra overhead for the server to maintain the state than the stateless
session bean.

Jan 2008 | Java Jazz Up | 16
 
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