Step #4:  Write the Enterprise JavaBeanTM Class

This is where the coding of the application (business logic) is done. Up until now, all we have done is to declare interfaces that the container tools will generate code for, but here is where the functionality of the JavaBean is coded.

One important thing to notice about our bean implementation is just how little code we have had to author. Most of this code is simply implementing methods from the EJB specification. It is easy to envisage templates and tools which do most of the implementation work for us. This is very comparable to the way tools have evolved for the GUI beans environment.

For our DemoBean EJB DemoBean.java looks like this (source):



 /**
 * DemoBean -- This is implemented by the EnterPrise
 * Bean author This class must extend
 * javax.ejb.SessionBean and implement
 * the methods in this interface as well as providing
 * the implementation of the business methods.
 *
 */
package ejb.demo;

import javax.ejb.*;
import java.io.Serializable;
import java.util.*;
import java.rmi.*;

public class DemoBean implements SessionBean { 
  static final boolean verbose = true; 

  private transient SessionContext ctx; 
  private transient Properties     props; 

  // Implement the methods in the SessionBean  
  // interface 
  public void ejbActivate()  { 
    if (verbose) 
      System.out.println("ejbActivate called"); 
  } 

  public void ejbRemove() { 
    if (verbose) 
      System.out.println("ejbRemove called"); 
  } 

  public void ejbPassivate() { 
    if (verbose) 
      System.out.println("ejbPassivate called"); 
  } 

  /** 
   * Sets the session context. 
   * 
   * @param                   SessionContext 
   */ 
  public void setSessionContext(SessionContext ctx) { 
    if (verbose) 
      System.out.println("setSessionContext called"); 
    this.ctx = ctx; 
    props    = ctx.getEnvironment(); 
  } 
 
  /** 
   * This method corresponds to the create method in  
   * the home interface DemoHome.java". 
   * The parameter sets of the two methods are 
   * identical. When the client calls 
   * DemoHome.create(), the container allocates an  
   * instance of the EJBean and calls ejbCreate(). 
   */ 
  public void ejbCreate () { 
    if (verbose) 
      System.out.println("ejbCreate called"); 
  } 

  /**  
   *   **** HERE IS THE BUSINESS LOGIC ***** 
   *  Do the demoSelect() but don't even go to  
   *  the database in this eg but instead just  
   *  return a String. 
   *  The really BIG thing to notice here is that     
   *  this is the only code we have invented at all  
   *  the rest of the code has been declarations  
   *  or simply implementing methods which are  
   *  part of the EJB interfaces and in this example  
   *  are not even used. 
   */ 
  public String demoSelect() 
    throws RemoteException 
  { 
    return("hello world"); 
  } 




 


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