how to avoid show buttons

this is my jsp

<%-- 
    Document   : Puchasing
    Created on : Apr 11, 2010, 12:34:23 PM
    Author     : aruna
--%>

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">

<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
        <table align="center">
            <tr><td>
                    <%
                        Double value = (Double) session.getAttribute("total");
                        if (value == 0.0 || value < 0.0) {
                            out.println("Thank You");
                        } else {
                            out.print("Your Total Credit");
                            out.print(session.getAttribute("total"));
                        }

%>
                </td></tr>
        </table>
        <br>

this is my calculate.java servlet

package zone;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class calculate extends HttpServlet {

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        Double total = 0.0;
        try {

String value = request.getParameter("action");
            HttpSession session = request.getSession();
            total = (Double) session.getAttribute("total");

if (value.equals("5p")) {
                total = total * 100 - 5;
            } else if (value.equals("10p")) {
                total = total * 100 - 10;
            } else if (value.equals("20p")) {
                total = total * 100 - 20;
            } else if (value.equals("50p")) {
                total = total * 100 - 50;
            } else if (value.equals("100p")) {
                total = total * 100 - 100;
            } else if (value.equals("200p")) {
                total = total * 100 - 200;
            }
            session.setAttribute("total", total/100);
           // out.write("total is  " + total);
            RequestDispatcher r = request.getRequestDispatcher("/Puchasing.jsp");
            r.forward(request, response);
        } finally {
            out.close();
        }
    }

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
     * Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

/** 
     * Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

/** 
     * Returns a short description of the servlet.
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}

there are many buttons and they have several values.
when i press button it decreases the total value.
when total is 0 the thank you message is appears.
when total is 0 i need to avoid rthe showing buttons.
how to do this?

In your Servlet you could set an attribute (request or session attribute) when total=0;

Then you get it on your jsp. If it's null the buttons are visible, if not they aren't.
In the same way. If that attribute you set in the Servlet is null you don't show the message. If it is not, you do show it.

In the Servlet:

The following is the jsp code:

(With the caveat that scriptlets aren't the cleanest way to do this--avoid them, including the bit from lines 19-28. No reason to do that in the JSP, and good reasons not to.

if it is not good way please tell me a good way?

Scriptlets are java code fragments. So, where do YOU think you should place them on?
You may use standard actions or JSTLs on the JSP, but not scriptlets.

Yes, right.

Assuming you have the same request attribute total0 set in your servlet

With the core library the test in your jsp could be written as follows:

Consider using Boolean.TRUE, and simplifying the conditional logic to just <c:when test="${total0}">.

in my servlet it get servlet using below code

then each request for clicking button it makes a new session
how to solve this issue?

Samanthi perera wrote:each request for clicking button it makes a new session

With all due respect, have you every seen the Servlet specification or the documentations of those classes? Which part of the documentation made you believe that getSession() always creates a new session?

I DON'T REMEMBER WHERE.But i heard that if we use
HttpSession session = request.getSession();
it makes a new session for each request.
if we use HttpSession session = request.getSession(false it gets the old session).

i change my servlet.java

package zone;

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class calculate extends HttpServlet {

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        Double total = 0.0;

try {

String value = request.getParameter("action");
            HttpSession session = request.getSession();
            total = (Double) session.getAttribute("total");

if (value.equals("5p")) {
                total = total * 100 - 5;
            } else if (value.equals("10p")) {
                total = total * 100 - 10;
            } else if (value.equals("20p")) {
                total = total * 100 - 20;
            } else if (value.equals("50p")) {
                total = total * 100 - 50;
            } else if (value.equals("100p")) {
                total = total * 100 - 100;
            } else if (value.equals("200p")) {
                total = total * 100 - 200;
            }

session.setAttribute("total", total / 100);
             if (total <= 0.0) {
                request.setAttribute("total0", new Boolean(true));
            }
            // out.write("total is  " + total);
            RequestDispatcher r = request.getRequestDispatcher("/Puchasing.jsp");
            r.forward(request, response);
        } finally {
            out.close();
        }
    }

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
     * Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

/** 
     * Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

/** 
     * Returns a short description of the servlet.
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>
}

now my jsp is like this

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">

<br>
    <c:choose>
        <c:when test="${total0==true}">
            <div align="center"> <h1>Thank you very much ccccccccccccccccccccccccccc</h1></div>
        </c:when>
        <c:otherwise>
            <div align="center"> Your Total Credit
                ${sessionScope["total"]}
            </div>
            <br>
            <br>
            <br>
            <table align="center">
                <tr><td>
                        <form action="calculate" method="post">
                            <input type="submit" name="action" value="5p" style="height: 25px; width: 100px"/>
                        </form>
                    </td></tr>
                <tr><td>
                        <form action="calculate" method="post">
                            <input type="submit" name="action" value="10p" style="height: 25px; width: 100px"/>
                        </form>
                    </td></tr>
                <tr><td>
                        <form action="calculate" method="post">
                            <input type="submit" name="action" value="20p" style="height: 25px; width: 100px"/>
                        </form>
                    </td></tr>
                <tr><td>
                        <form action="calculate" method="post">
                            <input type="submit" name="action" value="50p" style="height: 25px; width: 100px"/>
                        </form>
                    </td></tr>
                <tr><td>
                        <form action="calculate" method="post">
                            <input type="submit" name="action" value="100p" style="height: 25px; width: 100px"/>
                        </form>
                    </td></tr>
                <tr><td>
                        <form action="calculate" method="post">
                            <input type="submit" name="action" value="200p" style="height: 25px; width: 100px"/>
                        </form>
                    </td></tr>
            </table>
        </c:otherwise>
    </c:choose>

</c:if>

</body>
</html>

but it always print
Thank you very much ccccccccccccccccccccccccccc.
it can't be happen.because it is in c:choose part.how it happens?

Samanthi perera wrote:I DON'T REMEMBER WHERE.

Please KeepItDown.

Samanthi perera wrote:But i heard that if we use....

Do you thing listening to someone and believing whatever he say is better than going through the specifications or documentations to understand the truth?

Samanthi perera wrote:
HttpSession session = request.getSession();
it makes a new session for each request.
if we use HttpSession session = request.getSession(false it gets the old session)

Please go through the documentation of HttpServletRequest and read it.

Samanthi perera wrote:but it always print
Thank you very much ccccccccccccccccccccccccccc.
it can't be happen.because it is in c:choose part.how it happens?

Is their any taglib declaration for the JSTL core in your JSP?
I think you should have a look at the JSTL Tutorial.

if i run this is jps it print both falseee and otherwiseeeeeeeee

if i use this tooo same

Devaka Cooray wrote:Is their any taglib declaration for the JSTL core in your JSP?
I think you should have a look at the JSTL Tutorial.

it is ok now.
i have added
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> to the jsp and add jstl jar file.
not it is working.
when it comes to 0 value it prints thank you.
but after that if i click back button in the browser it shows the buttons and when i click it shows valus as minus valus.
how to avoid this?

It's ok.

If you set an attribute in a HttpServletRequest object it happens exactly as you are saying.
Once the request is gone, the attribute is gone as well.

Now, if you want, please try to put the attribute total0 in your session instead of in your request.

I mean:

1) Delete the statement:

2) add this one

It works as you expected it should.

And sorry i would like to add this too:

if you set an attribute in your session, it will stay there during your session life.
So, if your total value is not zero anymore and then you want to show your buttons again during the same session, remember to remove the attribute from your session.

For example, in your servlet you would do like that:

and your buttons will appear again.