Chapter: Java The Complete Reference - Applying Java - Introducing Servlets

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail

Reading Servlet Parameters

The ServletRequest interface includes methods that allow you to read the names and values of parameters that are included in a client request.

Reading Servlet Parameters

 

The ServletRequest interface 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 PostParameters.html, and a servlet is defined in PostParametersServlet.java.

The HTML source code for PostParameters.html is shown in the following listing. It defines a table that contains two labels and two text fields. One of the labels is Employee and the other is Phone. 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.

<html>

 

<body>

 

<center>

 

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

 

action="http://localhost:8080/examples/servlets/

 

servlet/PostParametersServlet">

 

<table>

 

<tr>

 

<td><B>Employee</td>

 

<td><input type=textbox name="e" size="25" value=""></td> </tr>

 

<tr>

 

<td><B>Phone</td>

 

<td><input type=textbox name="p" size="25" value=""></td> </tr>

 

</table>

 

<input type=submit value="Submit"> </body>

 

</html>

 

The source code for PostParametersServlet.java is shown in the following listing. The service( ) method is overridden to process client requests. The getParameterNames( ) method returns an enumeration of the parameter names. These are processed in a loop. You can see that the parameter name and value are output to the client. The parameter value is obtained via the getParameter( ) method.

 

import java.io.*; import java.util.*; import javax.servlet.*;

 

public class PostParametersServlet extends GenericServlet {

 

public void service(ServletRequest request, ServletResponse response)

 

throws ServletException, IOException {

 

// Get print writer.

 

PrintWriter pw = response.getWriter();

 

     Get enumeration of parameter names. Enumeration e = request.getParameterNames();

 

     Display parameter names and values. while(e.hasMoreElements()) {

 

String pname = (String)e.nextElement(); pw.print(pname + " = ");

 

String pvalue = request.getParameter(pname); pw.println(pvalue);

}

 

pw.close();

 

}

Compile the servlet. Next, copy it to the appropriate directory, and update the web.xml file, as previously described. Then, perform these steps to test this example:

 

            Start Tomcat (if it is not already running).

 

            Display the web page in a browser.

 

            Enter an employee name and phone number in the text fields.

 

            Submit the web page.

 

After following these steps, the browser will display a response that is dynamically generated by the servlet.

 

Study Material, Lecturing Notes, Assignment, Reference, Wiki description explanation, brief detail


Copyright © 2018-2020 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.