Show Parameter In Servlet

In this section, you will learn how to send and put all parameter names into the table. The following program uses two methods, which is described below.

Here, in this example, you will also see the use of getParameterNames() method and getParameterValues() method. The logic of the program will be written inside the doGet() method which takes two arguments, first is HttpServletRequest interface and the second one is the HttpServletResponse interface and this method can throw ServletException. First, it looks up all the parameter names via the getParameterNames() method of HttpServletRequest. This returns an Enumeration. Next, it loops down the Enumeration in the standard manner, using hasMoreElements() method to determine when to stop and using nextElement to get each entry. Since nextElement returns an Object, it casts the result to a String and passes that to getParameterValues, yielding an array of Strings. If that array is one entry long and contains only an empty string, then the parameter had no values, and the servlet generates an italicized "No Value" entry. The array takes more then one entry long, then the parameter had multiple values and they are displayed in a table list. Otherwise the one main value is just placed into the table.

getParameterNames(): getParameterNames() is a method. This is the method that returns the parameter names for the request as an enumeration of string .

getParameterValues: getParameterValues() is a method. This is the method that returns the values of the specified parameter for the request as an array of strings or null if the named parameter does not exit.


<html>

<head>

  <title>Form Post</title>

</head>



<body bgcolor="#FFFFFF">

<h1 align="center">A Sample FORM using POST</h1>



<form action="/amar/ShowParameterServlet" method="GET">

  Item Number:

  <input type="text" name="ItemNum"><br>

  Quantity:     

  <input type="text" name="Quantity"><br>

  <hr>

  First Name:

  <input type="text" name="FirstName"><br>



  Last Name:

  <input type="text" name="LastName"><br>

  Address:

  <textarea NAME="address" ROWS=3 COLS=40></textarea><br>

  Credit Card:<br>

    <input type="RADIO" name="CardType" value="Visa">Visa<br>

                

    <input type="RADIO" name="CardType" value="Master Card">Master Card<br>

                                        

    <input type="RADIO" name="CardType" value="India Express">India Express<br>

                                        

  Enter the Credit Card Number:

  <input type="password" name="CardNum"><br>

  Reenter the Credit Card Number:

  <input type="password" name="CardNum"><BR><BR>

  <center>

    <input type="submit" VALUE="Submit ">

  <input type ="reset" value= "Reset">

  </center>

</form>

</body>

</html>


import java.io.*;

import java.util.*;

import javax.servlet.*;

import javax.servlet.http.*;



public class ShowParameterServlet extends HttpServlet{

  public void doGet(HttpServletRequest request, HttpServletResponse response) 

                                             throws ServletException, IOException{

    response.setContentType("text/html");

        PrintWriter pw = response.getWriter();

    String title ="Reading all request parameter";

    pw.println("<html><head><title>" +

                "<body bgcolor=\"#FFFFFF\">\n" +

                "<H1 align=center>" + title + "</H1>\n" +

                "<table border=1 align=center>\n" +

                "<TR bgcolor=\"#8AEAF4\">\n" +

                "<td>Parameter Name</td><td>Parameter Value(s)</td>\n");

        Enumeration Names = request.getParameterNames();

    while(Names.hasMoreElements()) {

      String str = (String)Names.nextElement();

      pw.println("<tr><td>" + str + "</td><td>");

      String[] Values = request.getParameterValues(str);

      if (Values.length == 1) {

        String paramValue = Values[0];

        if (paramValue.length() == 0)

          pw.print("<I>No Value</I>");

        else

          pw.print(paramValue);

      }

      else {

        pw.println("<UL>");

        for(int i=0; i<Values.length; i++) {

          pw.println("<LI>" + Values[i]);

        }

        pw.println("</UL>");

      }

    }

    pw.println("</td></tr></table>\n</body></html>");

  }

}

<?xml version="1.0" encoding="ISO-8859-1"?>


<web-app>
<servlet>
<servlet-name>amar</servlet-name>
<servlet-class>ShowParameterServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>amar</servlet-name>
<url-pattern>/ShowParameterServlet</url-pattern>
</servlet-mapping>
</web-app>