Example 2: Developing of Stateful Session Bean

The purpose

Decision of the bean type

Development steps

1. Remote Interface:

      // File Counter.java
   
      public interface Counter extends javax.ejb.EJBObject {
        void increment() throws java.rmi.RemoteException;
        int value() throws java.rmi.RemoteException;
      }
    

2. Home Interface:

      // File CounterHome.java
   
      public interface CounterHome extends javax.ejb.EJBHome {
        Counter create(int initialValue)
          throws java.rmi.RemoteException, javax.ejb.CreateException;
      }
    

   Note the custom create() method with the numeric argument.

3. The Bean Class:

   // File CounterBean.java
   
   public class CounterBean implements javax.ejb.SessionBean {
   
     private javax.ejb.SessionContext _context;
     private int _value;
   
     public void setSessionContext(javax.ejb.SessionContext sessionContext)
      { _context = sessionContext; }
   
     public void ejbCreate(int initialValue) throws java.rmi.RemoteException 
      { _value=initialValue; }
   
     public void increment() throws java.rmi.RemoteException 
      { _value++; }
   
     public int value() throws java.rmi.RemoteException 
      { return _value; }
   
     // ...
     // empty implementations of ejbRemove(), ejbActivate() and ejbPassivate()
   }
   

4. The Client:

   // File CounerClient.java
   
   public class CounterClient {
   
     public static void main(String[] args) throws Exception {
   
       // get a JNDI context using the Naming service
       javax.naming.Context context = new javax.naming.InitialContext();
   
       Object ref = context.lookup("myCounterBean");
       CounterHome home = 
         (CounterHome) javax.rmi.PortableRemoteObject.narrow(ref, CounterHome.class);
   
       Counter c1 = home.create(0);
       Counter c2 = home.create(10);
   
       for (int i=0; i<10; i++) {
        c1.increment(); c2.increment();
      }
      
      System.out.println("c1="+c1.value()+", c2="+c2.value());
   
       c1.remove();
       c2.remove();
     }
   
   }
   

5. The deployment descriptor looks like in the previous example, only the < session-type > tag specifies the bean type as Stateful.
6. The process of the compilation, deployment and running of the bean in the container is the same as in the previous example

Hint: Try to redefine the Counter bean type as stateless and run it !