Embed Size (px)
Citation preview
Applet vs ServletPresenting by Bharat Sahu
MCA Vth Sem., MSIT
Outline• Applet
• Introduction• Life Cycle• Implementation
• Servlet• Introduction• Life Cycle• Implementation
• Difference Between Applet and Servlet
AppletIntroduction
• Applications are stand alone programs• Executed by Java Interpreter.
• Applet is small program• Can be placed on web page.• It will be executed by web browser.• Provide web page interactive content with power of Java.
• An applet is a Panel that allows interaction with a Java program.• A applet is typically embedded in a Web page and can be run
from a browser.• You need special HTML in the Web page to tell the browser
about the applet.
• Applets run in a sandbox: they have no access to the client’s file system.
• You can run Applet in any browser.• The best support isn't a browser, but the standalone program
appletviewer.
java.lang.Object
java.awt.Component
java.awt.Container
java.awt.Panel
java.applet.Applet
AppletClass Hierarchy
init()
start()
stop()
destroy()
Do Some Work
Life Cycle of An Applet
• Applet Method• public void init ()• public void start ()• public void stop ()• public void destroy ()• public void paint (Graphics g)note: repaint(), update()
import java.awt.*;import java.applet.*;
public class WelcomeApplet extends Applet {
public void init() {}
public void paint(Graphics g) {g.drawString("Welcome to Java Programming!",
25, 25 );}
}
<html><applet code = "WelcomeApplet.class" width = "300" height = "45"></applet> </html>
ServletIntroduction
• Server• Servers are those machine which is responds the clients request.
• Servlets – Web-based solutions executes by Server• Dynamically generate custom HTML documents• Replacement to CGI• Secure access to Website• Interact with databases• Servlet are as Applet but Server side
ServletHow it works?
• Client sends a request to server
• Server starts a servlet
• Servlet computes a result for server and does not quit
• Server returns response to client
• Another client sends a request
• Server calls the servlet again
Server
Client
Client
Servlet
• A servlet is any class that implements the javax.servlet.Servlet interface • In practice, most servlets extend the
javax.servlet.http.HttpServlet class• Some servlets extend javax.servlet.GenericServlet instead
• Tomcat is the Servlet Engine than handles servlet requests for Apache• It’s best to think of Tomcat as a “servlet container”
• Apache can handle many types of web services• Apache can be installed without Tomcat• Tomcat can be installed without Apache
Life cycle of ServletInitialization
(load resource)
Service(accept requests)
Destruction(unload resource)
• Initialize• Service• Destroy
ResponseRequest
• Initialize: init() method called once, when any request occur.• Service: Any requests will be forwarded to the service() method
• doGet()• doPost()• doDelete()• doOptions()• doPut()• doTrace()
• Destroy: called once• destroy() method called when: Application is stopped or Servlet container
shuts down• Allows resources to be free
import javax.servlet.*; import javax.servlet.http.*;import java.io.*;public class WelcomeServlet extends HttpServlet {
protected void doGet( HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
response.setContentType( "text/html" ); PrintWriter out = response.getWriter(); out.println( “<html><body>" );out.println( “<h1>Hello World</h1>" ); out.println( “</body></html>" );out.close}
}
Applet vs Servlet
• Similarities• Neither has a main()• Both have init() and destroy()• Both are part of a larger application made for the web
• Dissimilarity• Applets run on the client (browser) while servlets run on the
HTTP server• Applets are having limited functionality to look at the local file
system, establish network connections, etc.• Servlets are generally built to handle multiple clients at once,
whereas applets generally service one client at a time.• Servlets handle HTTP request• Applets used for static web pages, Servlet used for dynamic
web pages.
Reference
• Sun’s Website1. http://
java.sun.com/docs/books/tutorial/servlets/lifecycle/index.htm
2. http://java.sun.com/docs/books/tutorial/applets/lifecycle/index.htm
