Java Servlets - 2 minute tutorial

Let's write our first servlet.

A servlet must extend javax.servlet.http.HttpServlet class. Additoanally it must override method/s specific to the http method/s that it is supposed to handle. If a servlet handls HTTP GET request, it must overide doGet(HttpServletRequest , HttpServletResponse) method. The HttpServlet class is in the servlet-api.jar that can be obtained from the library folder of any web-server that implements servlet specification. In tomcat, servlet-api.jar is present in the $TOMCAT_HOME/lib or $TOMCAT/common/lib folder.

When a client makes an http request, the http web-server (for eg. tomcat) receives it, and calls the appropriate servlet class with an HttpServletRequest object and a HttpServletResponse object. The servlet can use the HttpServletResponse object to construct the http resposne or web-page that it needs to send to the http client. In the example below, the servlet gets a reference to the output stream of the http response using the getWriter() method and adds the content "Hi Friends" to the response.

package com.techfundaes.servletsBag;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class FirstServlet extends HttpServlet
{
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
	{
		PrintWriter pWriter = resp.getWriter();
		pWriter.println("Hi Friends");
	}
}