JavaRocks

This example shows how to write a simple program to print Hello World on web page.

 

Introduction : To write any servlet we need to use following files:

 

1. Deployment Descriptor (web.xml)
2. Servlet class (Implementation of HttpServlet class)
3. j2ee.jar or servlet-api.jar (generally comes with the webserver).
4. Web Server (Tomcat)
 

We will start by writing our Servlet class.

 

MyHelloWorld.java

 

package test;

 

import javax.servlet.http.HttpServlet;

import java.io.PrintWriter;

 

public class TestServlet extends HttpServlet {

    public void doGet(javax.servlet.http.HttpServletRequest httpServletRequest, javax.servlet.http.HttpServletResponse httpServletResponse) throws javax.servlet.ServletException, java.io.IOException{

        PrintWriter out=httpServletResponse.getWriter();

        out.print("Hello World");

    }

}

 
web.xml

 

<?xml version="1.0" encoding="ISO-8859-1"?>
<!--<!DOCTYPE web-app
 PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd"> -->

<web-app>
 <servlet>
  <servlet-name>MyHelloWorld</servlet-name>
  <servlet-class>test.MyHelloWorld</servlet-class>
 </servlet>
 <servlet-mapping>
 <servlet-name>Hello</servlet-name>
 <url-pattern>/HelloWorld</url-pattern>
 </servlet-mapping>
</web-app>

 

The above is the configuration of servlet in deployment descriptor.

&lt;servlet&gt; tag specify that test.MyHelloWorld is the servlet class and MyHelloWorld is its alias.

&lt;servlet-mapping&gt; specifies that whenever there is a request for /MyHelloWorld it should direct it to this servlet.

 

Put the compiled MyHelloWorld.class file in Tomcat/webapps/urAppName/WEB-INF/classes/test directory.

Put the jar files in Tomcat/webapps/urAppName/WEB-INF/lib directory.

 

Start the web server and run http://localhost:8080/urAppName/MyHelloWorld

 

It should show “Hello World “on the webpage.