be run simultaneously through several threads (there is no need for having a separate instance 

of a servlet object for each request; only a thread is directly associated with a request). 

A servlet is only removed from memory if it has not been requested over a longer period of time. 

Prior to removal, the servlet's destroy() method is called to allow for clean up activities. 

3.1.3  An Example Servlet 

Java servlets always look very similar. A servlet class usually contains just a few methods, the 

init(), a service(), and the destroy() method. If specific initialization or clean up activities are not 

required, the init() and destroy() methods may even be omitted. An example for a simple, but 

typical servlet class is shown below. This servlet reads a few parameters from the client 

request, performs a task, and generates the HTML output. 

package Rectangle;

// import the servlet packages

import javax.servlet.*;

import javax.servlet.http.*;

// import some other packages

import java.io.*;

import java.util.Arrays;

public class DrawRectangle extends HttpServlet {

// doGet method is an HTTP specific service() method

public void doGet(HttpServletRequest req, HttpServletResponse res)

throws ServletException, IOException {

// read two parameters from the request object

int width, height;

try {

width = Integer.parseInt(req.getParameter("width"));

height = Integer.parseInt(req.getParameter("height"));

}

catch (NumberFormatException e) { width = 10; height = 10; }

// perform action: generate a page & a rectangle with * characters

char line[] = new char[width];

Arrays.fill(line,'*');

StringBuffer str = new StringBuffer();

str.append("
");

for (int i=0; i