Developing Servlet Clients to our Enterprise JavaBeans
Gopalan Suresh Raj

Note
To work with any of these samples, you will need the following:
.........................................JDK 1.1.6 or higher (I use JDK 1.1.7A)
.........................................The EJBHome version0.5.1 (Scunthorpe)- a free EJB Server from http://www.ejbhome.com

To work with the EJB Servlet client, you will need
.........................................JSDK 2.0 or higher

The Steps involved in developing and deploying a Servlet client to our Enterprise Beans are:

1. Develop the client code.
2. Define the servlet properties.
3. Startup the EJB Server and the servlet runner.
4. Connect to the servlet from any standard web browser

A four-tier Architecture for a Typical Bank

Figure shows what we are trying to ultimately accomplish in these pages here.

1. Develop the servlet client code

Accounts.java
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;import java.rmi.*;
import java.util.*;
import Bank.*;

public class Accounts extends HttpServlet {
 TellerHome home = null;
 Teller teller = null;

 public void init() {
  try{
   home = (TellerHome)Naming.lookup("Teller");
   if( home == null )
   {
    System.out.println( "null TellerHome returned..." );
   }
   else
   {
    teller = home.create();
    System.out.println( "Naming.lookup successful..." );
    System.out.println( "home.create successful..." );
   }
  } catch(Exception e){System.out.println( e );}
 }

 public void doGet(HttpServletRequest req, HttpServletResponse res)
  throws ServletException, IOException
 {
  displayForm(res, "Welcome");
 }

 public void doPost(HttpServletRequest req, HttpServletResponse res)
  throws ServletException, IOException
 { double initialBalance = 0, transferAmount = 0;
   String customerName = null;
   int fromAccount = 0, toAccount = 0;
   boolean isCreate = false;
   if ("application/x-www-form-urlencoded".equals(req.getContentType())) {
    Enumeration enum = req.getParameterNames();
    while (enum.hasMoreElements()) {
     String name = (String) enum.nextElement(); System.out.println("name = " + name);

     String values[] = req.getParameterValues(name);
     if (values != null) {
      if( name.equals("initialBalance") )
      { initialBalance = (Double.valueOf(values[0])).doubleValue();
      }
      if( name.equals("customerName") )
      { customerName = values[0];
      } if( name.equals("transferAmount") )
        { transferAmount = (Double.valueOf(values[0])).doubleValue();
        }
        if( name.equals("fromAccount") )
        { fromAccount = Integer.parseInt( values[0]);
        }
        if( name.equals("toAccount") )
        { toAccount = Integer.parseInt( values[0]);
        } if( name.equals("createButton") )
          { isCreate = true;
          }
          if( name.equals("transferButton") )
          { isCreate = false;
          }
     }
    }
    System.out.println(" initialBalance = " + initialBalance +
                       " customerName = " + customerName+
                       " transferAmount = " + transferAmount+
                       " fromAccount = " + fromAccount+
                       " toAccount = " + toAccount+
                       " isCreate = " + isCreate);
    /**
    * Talk to the bean here
    */
    try{
        if( ( home == null ) || (teller == null) )
        {
         home = (TellerHome)Naming.lookup("Teller");
         teller = home.create();
        }
        if( isCreate == true ) { teller.createCheckingsAccount(customerName, initialBalance);
        }
        else
        {
         teller.TransferMoney( transferAmount, fromAccount, toAccount);
        }
       } catch(Exception e){ System.out.println( e ); }
   }
   displayForm(res, "Welcome");
 }

 private void displayForm(HttpServletResponse response, String message)
  throws IOException
 {
  if( ( home == null ) || (teller == null))
  {
   try{
    home = (TellerHome)Naming.lookup("Teller");
    teller = home.create();
   } catch(Exception e){ System.out.println( e ); }
  }
  response.setContentType("text/html");
  PrintWriter out = response.getWriter();
  out.println("<HTML><BODY>");
  out.println("<H1> List of Checking Accounts... </H1>");
  out.println("<body bgcolor=\"#FFFFFF\">");
  out.println("<table border=\"2\" width=\"100%\">");
  out.println("<tr><td align=\"center\" bgcolor=\"#C0C0C0\"><font size=\"3\"");
  out.println("face=\"Verdana\"><strong>Teller Number</strong></font></td>");
  out.println("<td align=\"center\" bgcolor=\"#C0C0C0\"><font size=\"3\"");
  out.println("face=\"Verdana\"><strong>Customer Name </strong></font></td>");
  out.println("<td align=\"center\" bgcolor=\"#C0C0C0\"><font size=\"3\"");
  out.println("face=\"Verdana\"><strong>Teller Balance </strong></font></td></tr>");
  System.out.println( "Checking List..." );
  int i = 0;
  Vector checkingList = null;
  try{
   checkingList = teller.getCheckingsList();
  }catch(Exception e){ System.out.println(e);}
  if(checkingList != null)
   for(i = 0; i < checkingList.size(); i++)
   {
    try{
     CheckingsPK key = (CheckingsPK)checkingList.elementAt(i);
     if(key == null)
      break;
     Checkings found = (Checkings)teller.getCheckings(key.account_number);
     if(found == null)
      break;
     System.out.println( " Account No = "+key.account_number+
                         " Name = "+found.getCustomerName()+
                         " Balance = " + found.getBalance() );
     out.println( "<tr><td><font size=\"1\" face=\"Verdana\"><strong>" + key.account_number +"</strong></font></td>" +
                  "<td><font size=\"1\" face=\"Verdana\"><strong>"+found.getCustomerName() +"</strong></font></td>" +
                  "<td><p align=\"right\"><font size=\"1\" face=\"Verdana\"><strong>"+ " $ " +found.getBalance() +"</strong></font></td>");

    }catch(Exception e){ System.out.println(e); break;}

   }
  out.println("</tr></table>");
  out.println("<p align=\"center\">");
  out.println("<font size=\"3\" face=\"Verdana\"><strong>Total Number of Checking Accounts = "+ i +" </strong></font></p>");
  System.out.println( "Listed all the "+ i + " records..." );

  out.println("<hr>");
  out.println("<H1> List of Savings Accounts... </H1>");
  out.println("<body bgcolor=\"#FFFFFF\">");
  out.println("<table border=\"2\" width=\"100%\">");
  out.println("<tr><td align=\"center\" bgcolor=\"#C0C0C0\"><font size=\"3\"");
  out.println("face=\"Verdana\"><strong>Teller Number</strong></font></td>");
  out.println("<td align=\"center\" bgcolor=\"#C0C0C0\"><font size=\"3\"");
  out.println("face=\"Verdana\"><strong>Customer Name </strong></font></td>");
  out.println("<td align=\"center\" bgcolor=\"#C0C0C0\"><font size=\"3\"");
  out.println("face=\"Verdana\"><strong>Teller Balance </strong></font></td></tr>");
  System.out.println( "Savings List..." );
  int j = 0;
  Vector savingsList = null;
  try{
   savingsList = teller.getSavingsList();
  }catch(Exception e){ System.out.println(e);}
  if(savingsList != null)
   for(j = 0; j < savingsList.size(); j++)
   {
    try{
     SavingsPK key = (SavingsPK)savingsList.elementAt(j);
     if(key == null)
      break;
     Savings found = (Savings)teller.getSavings(key.account_number);
     if(found == null)
      break;
     System.out.println( " Account No = "+key.account_number+
                         " Name = "+found.getCustomerName()+
                         " Balance = " + found.getBalance() );
     out.println( "<tr><td><font size=\"1\" face=\"Verdana\"><strong>" + key.account_number +"</strong></font></td>" +
                  "<td><font size=\"1\" face=\"Verdana\"><strong>"+found.getCustomerName() +"</strong></font></td>" +
                  "<td><p align=\"right\"><font size=\"1\" face=\"Verdana\"><strong>"+ " $ " +found.getBalance() +"</strong></font></td>");

    }catch(Exception e){ System.out.println(e); break;}

   }
  out.println("</tr></table>");
  out.println("<p align=\"center\">");
  out.println("<font size=\"3\" face=\"Verdana\"><strong>Total Number of Savings Accounts = "+ j +" </strong></font></p>");
  System.out.println( "Listed all the "+ j + " records..." );

  out.println("<hr>");

  out.println("<p align=\"center\"><font size=\"4\" face=\"Verdana\">");
  out.println("Create a New Teller</font></p>" );
  out.println("<form method=\"POST\">");
  out.println("<p align=\"center\"><font size=\"3\" face=\"Verdana\">");
  out.println("<strong>Enter Name <input type=\"text\" size=\"20\" name=\"customerName\">");
  out.println("Enter Initial Deposit </strong></font><font size=\"2\">");
  out.println("<strong><input type=\"text\" size=\"20\" name=\"initialBalance\"></strong></font></p>");
  out.println("<p align=\"center\"><font size=\"2\"><input type=\"submit\"");
  out.println("name=\"createButton\" value=\"Create\"></font></p>");
  out.println("</form><hr>");

  if((checkingList == null) || (savingsList == null))
  {
   out.println("</BODY></HTML>");
   return;
  }
  out.println("<p align=\"center\">");
  out.println("<font size=\"4\" face=\"Verdana\">");
  out.println("Transfer Money between Accounts</font></p>");

  out.println("<form method=\"POST\">");
  out.println("<p align=\"center\"><font size=\"3\" face=\"Verdana\">");
  out.println("<strong>Enter amount <input type=\"text\" size=\"20\" name=\"transferAmount\">");
  out.println("From Teller<select name=\"fromAccount\" size=\"1\">");
  System.out.println("Listing checking from");
  for(int k = 0; k < checkingList.size(); k++)
  {
   try{
    CheckingsPK found = (CheckingsPK)checkingList.elementAt(k);
    if(found == null)
     break;
    out.println("<option>" + found.account_number+ "</option>");
   }catch(Exception e){ System.out.println(e); break;}
  }
  System.out.println("Listing saving from");
  for(int k = 0; k < savingsList.size(); k++)
  {
   try{
    SavingsPK found = (SavingsPK)savingsList.elementAt(k);
    if(found == null)
     break;
    out.println("<option>" + found.account_number+ "</option>");
   }catch(Exception e){ System.out.println(e); break;}
  }

  out.println("</select> To Teller<select name=\"toAccount\" size=\"1\">");
  System.out.println("Listing checking to");
  for(int k = 0; k < checkingList.size(); k++)
  {
   try{
    CheckingsPK found = (CheckingsPK)checkingList.elementAt(k);
    if(found == null)
     break;
    out.println("<option>" + found.account_number+ "</option>");
   }catch(Exception e){ System.out.println(e); break;}
  }
  System.out.println("Listing saving to");
  for(int k = 0; k < savingsList.size(); k++)
  {
   try{
    SavingsPK found = (SavingsPK)savingsList.elementAt(k);
    if(found == null)
     break;
    out.println("<option>" + found.account_number+ "</option>");
   }catch(Exception e){ System.out.println(e); break;}
  }
  out.println("</select></strong></font><font size=\"2\">");
  out.println("<strong> </strong></font></p>");
  out.println("<p align=\"center\"><font size=\"2\"><input type=\"submit\"");
  out.println("name=\"transferButton\" value=\"Transfer\"></font></p>");
  out.println("</form>");

  out.println("<hr>");

  out.println("</BODY></HTML>");

 }
}

2. Define the servlet properties

servlet.properties
# @(#)servlets.properties 1.86 97/11/14
#
# Servlets Properties
#
# servlet.<name>.code=class name (foo or foo.class)
# servlet.<name>.initArgs=comma-delimited list of {name, value} pairs
# that can be accessed by the servlet using the
# servlet API calls
#
# session servlet
servlet.accounts.code=Accounts

3. Make sure the EJBServer is up and running and Startup the servlet runner


E:\MyProjects\AccountEJB>

E:\MyProjects\AccountEJB>servletrunner -p 6060 -d E:\MyProjects\AccountEJB -s servlet.properties
servletrunner starting with settings:
port = 6060
backlog = 50
max handlers = 100
timeout = 5000
servlet dir = E:\MyProjects\AccountEJB
document dir = .\examples
servlet propfile = servlet.properties

4. Open up your web browser - be it IE4.0x or Netscape 4.0x - and connect to the URL by typing the following into the Address


http://localhost:6060/servlet/Accounts

click here to go to
My EJB HomePage...

About the Author...
Gopalan Suresh Raj is a Software Architect, Developer and an active Author. He is contributing author to a couple of books "Enterprise Java Computing-Applications and Architecture" and "The Awesome Power of JavaBeans". His expertise spans enterprise component architectures and distributed object computing. Visit him at his Web Cornucopia© site (http://www.execpc.com/~gopalan) or mail him at gopalan@execpc.com.

 

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This site was developed and is maintained by Gopalan Suresh Raj

This page has been visited times since September 21,1998.

Last Updated : Dec 19, '98

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