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Stateless Session Beans - Complete Project

 Introduction

To improve performance, you might choose a stateless session bean if it has any of these traits:

  • The beanís state has no data for a specific client.
  • In a single method invocation, the bean performs a generic task for all clients. For example, you might use a stateless session bean to send an email that confirms an online order.
  • The bean fetches from a database a set of read-only data that is often used by clients. Such a bean, for example, could retrieve the table rows that represent the products that are on sale this month.
Types of Enterprise Beans are
  • Session Beans
    1.  Stateless Session Beans
    2. Stateful Session Beans
  • Entity Beans
    1. Bean Managed Persistent (BMP) Entity Beans
    2. Container Managed Persistent (CMP) Entity Beans
  • Message-Driven Bean
CLICK HERE to download this complete example (zip file)


 Create the Stateless Session Bean Home Interface (LoanHome.java)

import javax.ejb.EJBHome;
public interface LoanHome extends EJBHome
{
public Loan create() throws java.rmi.RemoteException, javax.ejb.CreateException;
}
Download: LoanHome.java

 Create the Stateless Session Bean Remote Interface (Loan.java)

import javax.ejb.EJBObject;
public interface Loan extends EJBObject
{
public float calculateInterest(float rate, float time, float amount) throws java.rmi.RemoteException;
}
Download: Loan.java

 Create the Stateless Session Bean Class (LoanBean.java)

import java.util.*;
import java.io.*;
import javax.ejb.SessionBean;
import javax.ejb.SessionContext;
public class LoanBean implements SessionBean
{
private javax.ejb.SessionContext m_ctx = null;
public void setSessionContext(SessionContext ctx)
{
m_ctx = ctx;
}
public void ejbCreate() throws java.rmi.RemoteException, javax.ejb.CreateException
{
System.out.println("ejbCreate() on obj " + this);
}
public void ejbRemove()
{
System.out.println("ejbRemove() on obj " + this);
}
public void ejbActivate()
{
System.out.println("ejbActivate() on obj " + this);
}
public void ejbPassivate()
{
System.out.println("ejbPassivate() on obj " + this);
}
public float calculateInterest(float rate, float time, float amount) throws java.rmi.RemoteException
{
float interest = time * amount * (rate / 100);
return interest;
}
}
Download: LoanBean.java

 Create the Web Client HTML File (Loan.html)

<HTML>
<BODY>
<FONT SIZE= 10 ALIGN=CENTER> <B> Calculate Interest </B> </FONT>
<FORM ACTION = "http://127.0.0.1:8080/loanctx/servlet/LoanServlet">
<TABLE>
<TR>
<TD> RATE </TD>
<TD> <INPUT TYPE = TEXT NAME = "rate"> </TD>
</TR>
<TR>
<TD> TIME </TD>
<TD> <INPUT TYPE = TEXT NAME = "time"> </TD>
</TR>
<TR>
<TD> AMOUNT </TD>
<TD><INPUT TYPE = TEXT NAME = "amount"> </TD>
</TR>
<TR>
<TD><INPUT TYPE = SUBMIT VALUE = "Calculate"></TD>
</TR>
</TABLE>
</FORM>
</BODY>
</HTML>
Download: Loan.html

 Create the Web Client Servlet (LoanServlet.java)

import java.io.*;
import javax.servlet.*;
import javax.naming.*;
import javax.servlet.http.*;
import javax.rmi.PortableRemoteObject;
import javax.ejb.*;
public class LoanServlet extends HttpServlet
{
public void doGet (HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException
{
PrintWriter out = response.getWriter();
response.setContentType("text/html");
float rate = Float.valueOf(request.getParameter("rate")).floatValue();
float time = Float.valueOf(request.getParameter("time")).floatValue();
float amount = Float.valueOf(request.getParameter("amount")).floatValue();
Loan myLoanRemote = null;
LoanHome myLoanHome = null;
InitialContext initContext = null;
try
{
initContext = new InitialContext();
}atch (Exception e)
{
out.println("First " + e.toString());
}
try
{
String JNDIName = "ejb/SimpleLoan";
Object obj = initContext.lookup(JNDIName);
myLoanHome = (LoanHome)PortableRemoteObject.narrow(obj, LoanHome.class);
}catch(Exception e)
{
out.println("Second " + e.toString());
}
try
{
myLoanRemote = myLoanHome.create();
}catch(CreateException e)
{
out.println("Third " + e.toString());
}
float interest = myLoanRemote.calculateInterest(rate, time, amount);
out.println("<B>Interest : " + interest + " </B>");
}
}
Download: LoanServlet.java


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