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Applet Vs Servlet
- 1. Applet vs Servlet Presenting by Bharat Sahu MCA Vth Sem., MSIT
- 2. Outline • Applet • Introduction • Life Cycle • Implementation • Servlet • Introduction • Life Cycle • Implementation • Difference Between Applet and Servlet
- 3. Applet Introduction • 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.
- 4. • 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.
- 6. 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()
- 7. 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>
- 8. Servlet Introduction • 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
- 9. Servlet How 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
- 10. • 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
- 11. Life cycle of Servlet Initialization (load resource) Service (accept requests) Destruction (unload resource) • Initialize • Service • Destroy Response Request
- 12. • 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
- 13. 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 } }
- 15. Applet vs Servlet • Similarities • Neither has a main() • Both have init() and destroy() • Both are part of a larger application made for the web
- 16. • 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.
- 17. Reference • Sun’s Website 1. http://java.sun.com/docs/books/tutorial/servlets/lifecycle/index.htm 2. http://java.sun.com/docs/books/tutorial/applets/lifecycle/index.htm
Hinweis der Redaktion
- Normal java program has main method on code. Applet doesn't have main method.
- Plateform independent Secure
- JApplet extends Applet Class
- Init(): execute first, initialize variables, best place define buttons, textfields, layouts, slider, every applet have init method. Start(): called after init, not always needed. Conjuction with strop(). Stop(): not always needed, called when browser leaves the page, called before destroy, conjuction with start(). Destroy(): Seldom needed, Called after stop( ), Use to explicitly release system resources (like threads), System resources are usually released automatically. Paint(): almost always needed, don’t call its called automatically call instead repaint, any painting done here or call by here. Repaint(): it’s a request that internally call update(Graphics g), any changes happened then call repaint.
- Servlet communicate to Clients and Server through HTTP
- About 50% and above websites uses Apache server Apache is server, tomcat is container; apache uses tomcat as container both are free source There is also other server available