Servlet

CGI (Common Gateway Interface)

CGI - Common Gateway Interface is used for generating dynamic content to the user.

CGI is used to execute a program that resider in the server to process data/access database to produce the relevent dynamic result.

CGI
Disadvantages of CGI
  • For each server request a process is created.
  • If no of request increase no of process will also increase. this will take more time and more memory.
  • Script are writen in native language like C, C++, etc.
  • CGI is platform dependent.

Servlet

Servlets are server side application that we develop using java language.
Server side application to be placed in web server or it should be placed in a application server.
To resolve the problem of CGI are reslove in java. Servlet are written in java. Java id flatform independent so servlet can run on any OS. In servlet thread is created for each request.

life cycle of servlet
Servlet VS CGI
Servlet CGI
It is thread based i.e. for every new request new thread is created. Thread is lightweight. It is process based i.e. for every new request new process is created. Process is heavy weight.
Servlet is Portable (platform independent) CGI is not Portable (platform dependent)
Can handle cookies and track session CGI can't handle cookies or session
Less expensive more expensive
Faster Slower
servlet

Servlet Example

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

// Extend HttpServlet class
public class HelloWorld extends HttpServlet {

public void init() throws ServletException {
// Do required initialization
}

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

response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<h1>" + message + "</h1>");
}

public void destroy() {
// do nothing.
} }