EJB 3.0 Tutorial

In this section we will read about the EJB. Here you will read about the various aspects of EJB. This section will describe you the various aspects of EJB that a beginner as well as experienced can learn from here.

EJB 3.0 Tutorial

Through this section you will learn the various aspects of EJB like what is an Enterprise Bean, what is EJB container, benefits of Enterprise Beans, when to use Enterprise Beans, types of Enterprise Beans.

What is Enterprise Beans

A Java EE component is called an Enterprise Beans which implements the EJB technology and runs inside an EJB container. Enterprise Beans are the server side component where the application's business logic is encapsulated. The business logic can be explained as, it is line of statement called code which is written for completing the requirements of application.

What is EJB Container

EJB container is a specification within the Application Server that runs the Enterprise Beans. Services provided by the EJB container is System-level services. In such type of services it provides the transaction and security to its enterprise beans. In addition they also provides for the Resource and life cycle management, remote accessibility, concurrency control, collision etc.

Benefits of Enterprise Beans

Generally, Enterprise beans is used for creating large, distributed applications. This is because of various reasons these are as follows :

  • The first reason is the services that are provided by the EJB container to enterprise beans i.e. System-level services that helps the developer to focus on solving the business problems.
  • The second reason is elaborated from first reason that the bean is responsible for application's business logic not for the client. So, a client developer can focus on only its presentation.
  • The third reason is enterprise bean's portability feature i.e. the enterprise beans components can be easily or conveniently portable.

When to use Enterprise Beans

Enterprise Beans should be used in any of the following requirements that an application is required :

  • Must be Scalable : The application must be scalable i.e. if users of your application is increasing and you may need to distribute applications components on multiple machines.
  • Data Integrity : The application must have to ensure the data integrity while transactions.
  • The client of the application is of different kinds.

Types of Enterprise Beans

Commonly the Enterprise Beans is of two types :

  • Session Bean : Session Bean implies that there is a single client inside the Application Server. Session Bean is responsible for doing tasks for a client that calls the session bean's methods of an application deployed on server. Session beans executes the business process within the server that protects the client from complicating the situation. A session bean is like an interactive session that can't be shared. A session bean is not persistent, it terminates with the client terminates. Session bean is of two types : Stateful Session Beans, Stateless Session Beans.
  • Message-Driven Bean : Message-Driven Bean permits the Java Enterprise Edition applications for processing messages asynchronously. Message-Driven beans likewise the JMS message listener, that receives the JMS messages rather than events.

You may read in detail about EJB 3.0 from here http://www.roseindia.net/ejb/