1. Java Servlets Lec 27

2. Creating a Simple Web Application in Tomcat

3. Tomcat Directory Structure myapp

4. Tomcat Setup Folder for HTML and JSP pages Folder for servlet and other java classes

5. Servlet Types Servlets are based on two main packages  javax.servlet  javax.servlet.http GenericServlet  For writing protocol independent servlets HttpServlet  Extends from GenericServlet class  Adds functionality for writing HTTP specific servlets

6. Servlet class hierarchy Object GenericServletServletResponse HttpServletRequest ServerRequest HttpServletHttpServletResponse javax.servlet javax.servlet.http

7. Writing Servlet Every servlet must implement the javax.servlet.Servlet interface  Contains the servlet’s life cycle methods etc. These are implemented by GenericServlet and HttpServlet classes Extend your servlet from one of these classes and add your own functionality public class MyServlet extends GenericServlet public class HelloServlet extends HttpServlet

8. Types of HTTP Requests  Get  Post  Delete  Options  Put  Trace

9. How HTTP Sends Request Client Server Servlets Some HTTP request types Get -- Attr/Val pairs attached after ? of URL E.g. http://www.gmail.com/register?name=ali Post -- Attr/Val pairs attatched with the request body

10. HTTP Request Example Request parameters etc

11. Writing Servlet Steps for making a HelloWorldServlet 1. Create a directory structure for your application (myapp). This is a one time process for any application 2. Create a HelloWorldServlet source file by extending this class from HttpServlet and override your desired method 3. Compile it (If compiler complains of not having required packages, check your class paths)

12. Writing Servlet Steps for making a HelloWorldServlet 1. Place the class file in the classes folder of your webapplication. (myapp) If you are using packages (recommended) then create a complete directory structure under classes folder 2. Create a deployment descriptor ( web.xml ) and put it inside WEB- INF folder 3. Restart your server, if already running 4. Access your application using Web browser

13. HelloServlet Example Code

14. HelloWorldServlet import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloWorldServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); out.println(“Hello World!”); }

15. web.xml HelloWorldServlet HelloWorldServlet /myfirstservlet

16. Compiling and Invoking Servlets Compile HelloWorldServlet.java using javac command Put HelloWorldServlet class in install_dir/webapps/myapp/WEB-INF/classes Put web.xml file in install_dir/webapps/myapp/WEB-INF Invoke your servlet by writing following command in the web browser http://localhost:8080/myapp/myfirstservlet

17. Lets do it LIVE

18. Free Servlet and JSP Engines Apache Tomcat  http://jakarta.apache.org/tomcat/ http://jakarta.apache.org/tomcat/ Allaire/Macromedia JRun  http://www.allaire.com/products/jrun http://www.allaire.com/products/jrun New Atlanta ServletExec  http://www.servletexec.com http://www.servletexec.com Causho’s Resin  http://www.caucho.com http://www.caucho.com