Asher Imtiaz Forman Christian College

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Web Application Development *Several of these slides have been adapted and modified from CSUN Comp595Web(Taehyung Wang) and LUMS cs391 (Umair Javed).

1 Web Application Development *Several of these slides have been adapted and modified from CSUN Comp595Web(Taehyung Wang) and LUMS cs391 (Umair Javed). Asher Imtiaz Forman Christian College JVM Client/ browser Server Request Servlet Response Extends the functionality of the server by Generating HTML pages dynamically 1

2 Anything that java can do (e.g. connect to database services) Handle data/requests sent by users (clients) Create and format results Send results back to user Advantages over other SSP technologies: Can use the Java APIs e.g. JDBC. Persistent between invocations, avoiding process instantiations. Portable across operating systems and servers. Good security. Is integrated closely with the J2EE environment. 2

3 To use Java servlets, following softwares will be needed J2SE Additional J2EE based libraries for servlets such as servletapi.jar, jsp-api.jar. You can download these APIs separately but theyarealsoavailablewiththewebserveryou llbeusing. A capable servlet web engine(web server) Environment Setting(Handout on wiki) Web Application Development 3

4 my-app myapp Folder for HTML and JSP pages Folder for servlet and other java classes 4

5 Servlet Types Generic servlets javax.servlet HTTP servlets javax.servlet.http Every servletmust implement the javax.servlet.servlet interface Most servlets implement this interface by extending one of two special classes: javax.servlet.genericservlet or javax.servlet.http.httpservlet Unlike a regular Java program, and just like an applet,aservletdoesnothaveamain()method. Instead, each time the server dispatches a request to a servlet, it invokes the servlet s service() method. 5

6 A generic servlet should override its service() method to handle requests as appropriate for the servlet. AnHTTPservletusuallydoesnotoverridethe service() method. Instead, it overrides doget() to handle GET requests and dopost() to handle POST requests. Object GenericServlet ServerRequest ServletResponse javax.servlet HttpServlet javax.servlet.http HttpServletRequest HttpServletResponse 6

7 Steps for making a HelloWorld servlet 1. Create a directory structure for your application (myapp). This is a one time process for any application 2. Create a HelloWorldsource 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) Steps for making a HelloWorld servlet 1. Place the class file in the classesfolder 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 7

8 import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloWorld extends HttpServlet { public void doget(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getwriter(); out.println( Hello World! ); public class HelloWorldExextends HttpServlet{ protected void processrequest(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); PrintWriter out = response.getwriter(); try { out.println("<html>"); out.println("<head>"); out.println("<title>servlet HelloWorld</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>servlet HelloWorld at " + request.getcontextpath () + "</h1>"); out.println("</body>"); out.println("</html>"); finally { out.close(); 8

9 <?xml version="1.0" encoding="iso "?> <web-app> <servlet> <servlet-name>helloworldservlet</servlet-name> <servlet-class>helloworld</servlet-class> </servlet> <servlet-mapping> <servlet-name>helloworldservlet</servlet-name> <url-pattern>/myfirstservlet</url-pattern> </servlet-mapping> </web-app> Compile HelloWorld.java using javac command Put HelloWorldclass in install_dir/webapps/myapp/web-inf/classes Put web.xml file in install_dir/webapps/myapp/web-inf Invoke your servletby writing following command in the web browser Or 9

Principles and Techniques of DBMS 5 Servlet

Principles and Techniques of DBMS 5 Servlet Haopeng Chen REliable, INtelligentand Scalable Systems Group (REINS) Shanghai Jiao Tong University Shanghai, China http://reins.se.sjtu.edu.cn/~chenhp e- mail: