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EJB 3.0
 
 

• In this tutorial, you will learn how a stateless EJB application is developed using an Application Server Jboss 4.2.0. So lets first see the life cycle of a
Stateless Session Bean.

Life Cycle of a Stateless Session Bean:

Since the Stateless session bean does not passivates across method calls therefore a stateless session bean includes only two stages. Whether it does not exist or ready for method invocation. A stateless session bean starts its life cycle when the client first obtains the reference of the session bean. For this, the container performs the dependency injection before invoking the annotated @PreConstruct method if any exists. After invoking the annotated @PreConstruct method the bean will be ready to invoke its method by the client.

The above figure demonstrates how the Stateless Session Beans are created and destroyed.

The container calls the annotated @PreDestroy method while ending the life cycle of the session bean. After this, the bean is ready for garbage collection.

In this tutorial, we are going to develop a Stateless Session Bean Application named example. The purpose of example is to perform the mathematical operations such as Addition, Subtraction, Multiplication, and Division.

 

The example application consists of an enterprise bean, which performs the calculations, and a web client.

There are following steps that you have to follow to develop a calculator JEE application.

1. Create the enterprise bean: CalculatorBean
2. Create web clients: index.jsp, form.jsp, WebClient.jsp
3. Deploy example onto the server.
4. Using a browser, run the web client.

1.Creating the enterprise bean:
The enterprise bean in our example is a stateless session bean called CalculatorBean. The source code for CalculatorBean is in “com.javajazz/examples/ejb3/stateless” directory.

Creating CalculatorBean requires these steps:

1) Coding the bean’s Remote business interface and Enterprise bean class.

2) Compiling the source code with the Ant tool.

(i) Coding the Business Interface

The business interface defines the business methods that a client can call remotely. The business methods are implemented in the enterprise bean class. The source code for the CalculatorRemote business interface is given
below.

package
com.javajazzup.examples.ejb3.stateless;
import java.math.*;
import javax.ejb.Remote;
import java.lang.annotation.*;
@Remote
public interface CalculatorRemote {
public float add(float x, float y);
public float subtract(float x, float y);
public float multiply(float x, float y);
public float division(float x, float y);
}

 

Jan 2008 | Java Jazz Up | 17
 
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