1. 20-Nov-15introServlets.ppt Intro to servlets

2. 20-Nov-15introServlets.ppt typical web page – source Hello Hello

3. 20-Nov-15introServlets.ppt HTTP client-server model web client (browser) web server (Apache) HTTP request HTTP response

4. 20-Nov-15introServlets.ppt HyperText Transport Protocol (HTTP) client-server scenario a web server is a program plays the role of “server” runs all the time but does nothing much listens on some TCP port until called if called, formulates an answer and sends it to the client as a string (or stream or file) a web browser is a program plays the role of “client” runs if a user starts it if the user instructs clicks something: 1.sends a URL to a web server 2.waits to receive a plain text file from from web server 3.formats (displays) the contents of the received file (string or stream) 4.the three steps above may be repeated if the page contains images by file, string or stream, I mean: a one-dimensional array of printable characters

5. 20-Nov-15introServlets.ppt servlet URL General form: http://serverName:port/contextName Example: http://harborsparrow.com:80/hello port context Typical: http://harborsparrow.com/hello context

6. 20-Nov-15introServlets.ppt Java web application web client (browser) HTTP request HTTP response web server (Apache) 1 = ServletContext object 2 = HttpServletRequest object 3 = HttpServletResponse object 4 = HttpServlet object 5 = web.xml file 2 3 4 1 servlet container (Tomcat) 5

7. 20-Nov-15introServlets.ppt Java web application web client (browser) HTTP request HTTP response web server (Apache) 1 = ServletContext object 2 = HttpServletRequest object 3 = HttpServletResponse object 4 = HttpServlet object 5 = web.xml file 2 3 4 1 servlet container (Tomcat) 5

8. 20-Nov-15introServlets.ppt Java web application that calls across the network to something else web client (browser) HTTP request HTTP response web server (Apache) 1 = ServletContext object 2 = HttpServletRequest object 3 = HttpServletResponse object 4 = HttpServlet object 5 = web.xml file 2 3 4 1 servlet container (Tomcat) 5 remote computer (database or other)

9. 20-Nov-15introServlets.ppt Hello servlet

10. 20-Nov-15introServlets.ppt code public class Hello extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println(" "); out.println("Hello"); out.println(" "); out.println("Hello"); out.println(" "); } /* end doPost */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { doPost(request,response); } /* end doGet */ } // end class

11. 20-Nov-15introServlets.ppt web.xml (deployment descriptor) for Tomcat <web-app xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" version="2.4"> Hello Hello /servlet/Hello

12. 20-Nov-15introServlets.ppt directory structure for Tomcat

13. 20-Nov-15introServlets.ppt the end of this PowerPoint file Hooray!