Web service using Java Servlets

Rajesh Devadas, Nandhini
Arumugam & Sujata De

Servlet is a Java program that extends the functionality of a Web server, generating dynamic content and interacting with Web applications using a request-response paradigm. Creating a Web service from a servlet involves deploying the servlet in
Weblogic. The example of HelloWorld Servlet is given below.

import javax.servlet.ServletContext;

import javax.servlet.ServletException;

import
javax.servlet.http.HttpServletRequest;

import
javax.servlet.http.HttpServletResponse;

import javax.servlet.http.HttpServlet;

import java.io.IOException;

import java.io.*;

public class HelloWorldServlet extends HttpServlet

{

public void doGet(HttpServletRequest request,HttpServletResponse response) throws
IOException, ServletException

{

response.setContentType("text/html");

PrintWriter out =
response.getWriter();

out.println("HelloWorld");

out.close();

}

public void doPost(HttpServletRequest request,HttpServletResponse response) throws
IOException, ServletException

{

doGet(request,response);

}

}

HelloWorldServlet.java

Copy the HelloWorldServlet.java into HelloWorldServlet directory. Compile the java file into HelloWorldServlet/Web-inf/classes directory. Make sure that Servlet.jar is there in the CLASSPATH before compiling. The deployment descriptor needed for Servlet deployment is Web.xml. It is given below.

Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/Web-app_2_3.dtd">

HelloWorldServlet

HelloWorldServlet

HelloWorldServlet

HelloWorldServlet

/ HelloWorldServlet /*

Web.xml

In case of parameters you can also set these tags in Web.xml

name

nandhu

The directory structure that is needed for deploying a servlet is as follows:

HelloWorldServlet

Web-Inf

Classes

HelloWorldServlet.class

Web.xml

In the Weblogic administration console, select Web Application Modules under Deployment and select Deploy a new Web Application Module. Select the directory HelloWorldServlet and click Target Module. Click Deploy. Wait for few seconds till the success message gets displayed. Now the servlet is deployed. It can be tested with the URL : http://hostname:port/HelloWorldServlet/HelloWorldServlet . "Hello world" will be displayed in the browser.

**Watch out for the next tutorial,
which will cover creating a Web
service from JSP and HTML**

The authors are working as Software
Engineers with Hewlett-Packard India Software Operations Ltd., in Bangalore and
have expertise in the areas of Web services and other J2EE technologies.