Writing Servlet Hello World

We should start understanding the servlets from the
beginning. Lets start by making one program which will just print the
"Hello World" on the browser. Each time the user visits this page it
will display "Hello World" to the user.
As we know that the our servlet extends the HttpServlet
and overrides the doGet() method which it inherits from the HttpServlet
class. The server invokes doGet() method whenever web server recieves the
GET request from the servlet. The doGet() method takes two arguments first is
HttpServletRequest object and the second one is HttpServletResponse object and
this method throws the ServletException.
Whenever the user sends the request to the server then
server generates two obects, first is HttpServletRequest object and the second
one is HttpServletResponse object. HttpServletRequest object represents the
client's request and the HttpServletResponse represents the servlet's
response.
Inside the doGet(() method our servlet has first used
the setContentType() method of the response object which sets the content
type of the response to text/html. It is the standard MIME content type
for the Html pages. After that it has used the method getWriter() of the
response object to retrieve a PrintWriter object. To display the
output on the browser we use the println() method of the PrintWriter
class.
The code the program is given below:
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class HelloWorld extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException,IOException{
response.setContentType("text/html");
PrintWriter pw = response.getWriter();
pw.println("<html>");
pw.println("<head><title>Hello World</title></title>");
pw.println("<body>");
pw.println("<h1>Hello World</h1>");
pw.println("</body></html>");
}
}
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web.xml file for this program:
<?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>Hello</servlet-name>
<servlet-class>HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Hello</servlet-name>
<url-pattern>/HelloWorld</url-pattern>
</servlet-mapping>
</web-app>
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The output of the program is given below:
Download this example:

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