Making a Servlet display a JSP Page on first request (Servlets forum at Coderanch)

Ray mann

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Posts: 55

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posted 7 years ago

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Hi Guys,
I would like some help with my Servlet as I would like my Servlet to run first and to create a session var then forward the value to the JSP (the GUI ) and have the JSP able to send a var back to the Servlet for reprocessing
and update the session var to again be sent to the JSP and so on . - The Servlet contains logic to handle incorrect input types and directly out puts a HTML error page...hope this makes sense!

Below I will add the code I have so far and a link to the question in my Text Book.

My code:

JSP Page:

bank.JSP :

<%
	//Starts outputting the HTML Form
%>
<html>
  <head>
    <title>Online Bank Simulator</title>
  </head>
  <body>
    <hr color="#808000">
      <center>
        <h1>Banking Simulation</h1>
      </center>
        
        
      <form method="POST" action="../servlet/JSPBank">
        <center>Amount: <input type="text" name="Amount" size="20"></center>
	<% 
          <p>Balance:
          //       out.println(session.getAttribute("accBalance"));
          </p>
        %>

Servlet :

JSPBank.java :

import java.lang.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.net.*;
import java.text.DecimalFormat;

public class JSPBank extends HttpServlet //throws ServletException, IOException
{

DecimalFormat myFormat = new DecimalFormat("$#,000.00");

public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException
    {
        doPost(request,response);
    }

public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException
    {
        //Makes instance variable a local variable

//Set MIME type of content returned to browser
        HttpSession session = request.getSession();

response.setContentType("text/html");

PrintWriter out = response.getWriter();

//Starts outputting the HTML Form

//Decides which action to take

double accBalance = 0.0;
		Double savedBalance = (Double)session.getAttribute("accBalance");

if (savedBalance != null)
		{
		    accBalance = savedBalance.doubleValue();
		}

String action = request.getParameter("act");

if(action != null)
        {
            if(action.equals("Deposit"))
            {
             	double amount;
			    String strAmount = request.getParameter("Amount");
				try
				{
				amount = Double.parseDouble(strAmount);

if(amount <= 0.00)
                  {
				 	 //Output error HTML Page
				  	 out.println("<html>");
				 	 out.println("<head>");
				 	 out.println("<title>Invalid Input</title>");
				  	 out.println("</head>");
				  	 out.println("<body>");
				  	 out.println("");
                  	 out.println("<h3>Invalid Input</h3>");
                  	 out.println("<p>Please note that if you are seeing this page it means that you have attempted to Deposit a invalid amount!!<br/>Below is a list of invalid inputs</p>");
                  	 out.println("<ul>");
                  	 out.println("<li>Blank or null values</li>");
                  	 out.println("<li>Negative Numbers</li>");
                  	 out.println("<li>Words or Letters </li>");
                  	 out.println("<li>Special charaters</li>");
                   	 out.println("</ul>");
                  	 out.println("<br/>");
                  	 out.println("<h3>Sugestions</h3>");
                  	 out.println("<p>Inorder to avoid seeing this error page again please only input numbers and avoid inputing the above listed input types</p>");
              	  }
              	  else
              	  {
                   accBalance = accBalance + amount;

session.removeAttribute("accBalance");
				    session.setAttribute("accBalance",new Double(accBalance));

session.setAttribute("forwardTo","bank.jsp");

//out.println("<br><center>Balance:"+myFormat.format(accBalance)+" </center> <br>");
       	          }
       	          }
			  catch(NumberFormatException ex)
			  	{
					//Output error HTML Page
				 	out.println("<html>");
					out.println("<head>");
					out.println("<title>Invalid Input</title>");
					out.println("</head>");
					out.println("<body>");
					out.println("");
					out.println("<h3>Invalid Input</h3>");
					out.println("<p>Please note that if you are seeing this page it means that you have attempted to Deposit a invalid amount!!<br/>Below is a list of invalid inputs</p>");
					out.println("<ul>");
					out.println("<li>Blank or null values</li>");
					out.println("<li>Negative Numbers</li>");
					out.println("<li>Words or Letters </li>");
					out.println("<li>Special charaters</li>");
					out.println("</ul>");
					out.println("<br/>");
					out.println("<h3>Sugestions</h3>");
                    out.println("<p>Inorder to avoid seeing this error page again please only input numbers and avoid inputing the above listed input types</p>");
				}
            }
            else if(action.equals("Withdraw"))
            {

double amount;
				String strAmount = request.getParameter("Amount");
				try
				{
					amount = Double.parseDouble(strAmount);

if(amount <= 0.00)
                {
					//Output error HTML Page
                    out.println("<html>");
					out.println("<head>");
					out.println("<title>Invalid Input</title>");
					out.println("</head>");
					out.println("<body>");
					out.println("");
					out.println("<h3>Invalid Input</h3>");
					out.println("<p>Please note that if you are seeing this page it means that you have attempted to Withdraw a invalid amount!!<br/>Below is a list of invalid inputs</p>");
					out.println("<ul>");
					out.println("<li>Blank or null values</li>");
					out.println("<li>Negative Numbers</li>");
					out.println("<li>Words or Letters </li>");
					out.println("<li>Special charaters</li>");
					out.println("</ul>");
					out.println("<br/>");
					out.println("<h3>Sugestions</h3>");
                  	out.println("<p>Inorder to avoid seeing this error page again please only input numbers and avoid inputing the above listed input types</p>");

}
               else
                {
                    accBalance = accBalance - amount;

session.removeAttribute("accBalance");
        			session.setAttribute("accBalance",new Double(accBalance));

session.setAttribute("forwardTo","bank.jsp");
                   // out.println("<br><center>Balance:"+myFormat.format(accBalance)+" </center> <br>");

}
                }
				catch(NumberFormatException ex)
				{
					//Output error HTML Page
					out.println("<html>");
					out.println("<head>");
					out.println("<title>Invalid Input</title>");
					out.println("</head>");
					out.println("<body>");
					out.println("");
					out.println("<h3>Invalid Input</h3>");
					out.println("<p>Please note that if you are seeing this page it means that you have attempted to Withdraw a invalid amount!!<br/>Below is a list of invalid inputs</p>");
					out.println("<ul>");
					out.println("<li>Blank or null values</li>");
					out.println("<li>Negative Numbers</li>");
					out.println("<li>Words or Letters </li>");
					out.println("<li>Special charaters</li>");
					out.println("</ul>");
					out.println("<br/>");
					out.println("<h3>Sugestions</h3>");
                  	out.println("<p>Inorder to avoid seeing this error page again please only input numbers an avoid inputing the above listed input types</p>");

}
            }
            else if(action.equals("Balance"))
            {
				session.setAttribute("forwardTo","bank.jsp");
                //out.println("<br><center>Balance:"+myFormat.format(accBalance)+" </center> <br>");
            }
            else
            {	session.setAttribute("forwardTo","bank.jsp");
                //out.println("<br><center>Balance:"+myFormat.format(accBalance)+" </center> <br>");
            }
        }
        else
        {
			session.setAttribute("forwardTo","bank.jsp");
            //out.println("<br><center>Balance:"+myFormat.format(accBalance)+" </center> <br>");
        }

session.removeAttribute("accBalance");
        session.setAttribute("accBalance",new Double(accBalance));

}

}//end class

The Question is no 7 on this page : Text Book
Hope this helps you to understand what i am trying to achieve .

Thanks in advanced for any and all help!!

Ray mann

Ranch Hand

Posts: 55

I like...

posted 7 years ago

Number of slices to send:

Optional 'thank-you' note:

Send

Awesome Thanks it did the trick!!

Now its almost right ...for some reason the transactions always seem to be one transaction behind eg. if I start on a 0.00 balance then deposit 100 then it displays 0.00 balance then I deposit 50 it displays a balance of 100.00 then I deposit 10 it shows a balance of 150.00 and so on ....

And the error handling (incorrect input type detection) is not working no matter what.

bank.jsp

<%
	//Starts outputting the HTML Form
%>
<html>
  <head>
    <title>Online Bank Simulator</title>
  </head>
  <body>
    <hr color="#808000">
      <center>
        <h1>Banking Simulation</h1>
      </center>
        
        
      <form method="POST" action="../servlet/JSPBank">
        <center>Amount: <input type="text" name="Amount" size="20"></center>
	<center>
          <p>Balance:
          	<%       out.println(session.getAttribute("accBalance"));   %>
          <p/>
        </center>

JSPBank.java

import java.lang.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
import java.net.*;
import java.text.DecimalFormat;

public class JSPBank extends HttpServlet //throws ServletException, IOException
{

DecimalFormat myFormat = new DecimalFormat("$#,000.00");

public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException
    {
        doPost(request,response);
    }

public void doPost(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException
    {

//Set MIME type of content returned to browser

HttpSession session = request.getSession();

response.setContentType("text/html");

PrintWriter out = response.getWriter();

//Starts outputting the HTML Form

RequestDispatcher requestDispatcher = request.getRequestDispatcher("../bank.jsp");
		requestDispatcher.forward(request, response);