SWAPNA MEDIKONDA: Reading Servlet Parameters

Reading Servlet Parameters :

The ServletRequest class includes methods that allow you to read the names and values of parameters that are included in a client request. We will develop a servlet that illustrates their use.

The example contains two files.

A Web page is defined in sum.html and a servlet is defined in Add.java

sum.html:

<html>

<body>

<form name="Form1" method="post"

action="Add">

<table>

<tr>

<td><B>Enter First Number</td>

</tr>

<tr>

<td><B>Enter Second Number</td>

</tr>

</table>

</body>

</html>

The HTML source code for sum.html defines a table that contains two labels and two text fields. One of the labels is Enter First Number,and the other is Enter Second Number. There is also a submit button. Notice that the action parameter of the form tag specifies a URL. The URL identifies the servlet to process the HTTP POST request.

Add.java

import java.io.*;

import java.util.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class Add

extends HttpServlet

{

public void doPost(HttpServletRequest request,

HttpServletResponse response)

throws ServletException, IOException

{

// Get print writer.

response.getContentType("text/html");

PrintWriter pw = response.getWriter();

// Get enumeration of parameter names.

Enumeration e = request.getParameterNames();

// Display parameter names and values.

int sum=0;

while(e.hasMoreElements())

{

String pname = (String)e.nextElement();

pw.print(pname + " = ");

String pvalue = request.getParameter(pname);

sum+=Integer.parseInt(pvalue);

pw.println(pvalue);

}

pw.println("Sum = "+sum);

pw.close();

}

The source code for Add.java contains doPost( ) method is overridden to process client requests. The getParameterNames( ) method returns an enumeration of the parameter names. These are processed in a loop.we can see that the parameter name and value are output to the client. The parameter value is obtained via the getParameter( ) method.

after typing URL : http://localhost:9999/servlets/sum.html