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Dickson K.W. Chiu PhD, SMIEEE Reference: Sun J2EE 1.4 Tutorial

CSIT600b: XML Programming XML Programming Guide: Getting Started. Dickson K.W. Chiu PhD, SMIEEE Reference: Sun J2EE 1.4 Tutorial . J2EE Environment – a Standard. Distributed multi-tiered applications Widely deployed and supported by many products

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Dickson K.W. Chiu PhD, SMIEEE Reference: Sun J2EE 1.4 Tutorial

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  1. CSIT600b: XML Programming XML Programming Guide: Getting Started Dickson K.W. Chiu PhD, SMIEEE Reference: Sun J2EE 1.4 Tutorial

  2. J2EE Environment – a Standard • Distributed multi-tiered applications • Widely deployed and supported by many products • IBM Websphere, Sun Java studio, Borland Jbuilder, etc. Dickson Chiu 2004

  3. J2EE Containers and API Container = platform / runtime environment Dickson Chiu 2004

  4. Simplified Systems Integration • Platform-independent, not to lock customers into their technologies • The J2EE APIs enable systems and applications integration through the following: • Unified application model across tiers with enterprise beans • Simplified request-and-response mechanism with JSP pages and servlets • Reliable security model with JAAS • XML-based data interchange integration with JAXP, SAAJ, and JAX-RPC • Simplified interoperability with the J2EE Connector architecture • Easy database connectivity with the JDBC API • Enterprise application integration with message-driven beans and JMS, JTA, and JNDI Dickson Chiu 2004

  5. Packaging J2EE Application • Deployment Descriptors can be changed for software configuration without changing the source code Dickson Chiu 2004

  6. Java Web Application Overview • Servlets are basics • Web Components in web containers Dickson Chiu 2004

  7. Advantages of Java Servlet • Performance: VM always running, servlet objects persist instead of continually created/destroyed as CGI are • Stateful: can more easily track session information since same servlet object used • Portable: since written in Java • Security: SecurityManager can constraint servlets in manner similar to applets • Servlets also have all the advantages of Java: runtime safety, built on extensive class libraries, networking, threads, etc. Dickson Chiu 2004

  8. javax.servletpackage Servlets • Servlet interface: declares servlet methods (init, service, etc.) • GenericServlet implements Servlet • HttpServlet subclass adds features specific to HTTP • Technically, an servlet is a program that extends either GenericServlet or HttpServlet. GenericServlet HttpServlet YourServlet Dickson Chiu 2004

  9. javax.servlet.httpPackage Implement your own • HTTP requests include – GET (default), conditional GET, HEAD, POST, PUT, DELETE, TRACE, OPTIONS • All methods take two arguments: • an HttpServletRequest object • an HttpServletResponse object • Return a BAD_REQUEST (400) error by default (i.e., if you don’t have your own implementation) Dickson Chiu 2004

  10. Java Servlet Example – Hello World package servlets; import java.io.*; import java.util.*; import java.sql.*; import javax.servlet.*; import javax.servlet.http.*; public class GreetingServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); response.setBufferSize(8192); PrintWriter out = response.getWriter(); // then write the data of the response out.println("<html>" + "<head><title>Hello</title></head>"); out.println("<body bgcolor=\"#ffffff\">" + "<img src=\"duke.waving.gif\" alt=\"Duke waving\">" + "<h2>Hello, my name is Duke. What's yours?</h2>" + "<form method=\"get\">" + "<input type=\"text\" name=\"username\" size=\"25\">" + "<p></p>" + "<input type=\"submit\" value=\"Submit\">" + "<input type=\"reset\" value=\"Reset\">" + "</form>"); Specify target page if necessary Dickson Chiu 2004

  11. Java Servlet Example – cont String username = request.getParameter("username"); if ((username != null) && (username.length() > 0)) { RequestDispatcher dispatcher = getServletContext().getRequestDispatcher("/response"); if (dispatcher != null) { dispatcher.include(request, response); } } out.println("</body></html>"); out.close(); } public String getServletInfo() { return "The Hello servlet says hello."; } } Stuff the output of another servlet to here Dickson Chiu 2004

  12. Java Servelet Example - Response // import not shown here public class ResponseServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); // then write the data of the response String username = request.getParameter("username"); if ((username != null) && (username.length() > 0)) { out.println("<h2>Hello, " + username + "!</h2>"); } } public String getServletInfo() { return "The Response servlet says hello."; } } Parameters passed with request / response objects Dickson Chiu 2004

  13. Servlet Life Cycle • Servlets are controlled by servers • A server loads and initializes the servlet • The servlet handles zero or more client requests • The server terminates the servlet Dickson Chiu 2004

  14. Servlet Life Cycle (2) The server will automatically called : • public void init(): • Called only once when serlvet is being created. • Good place for set up, open Database, etc. • public void service(): • Called once for each request. • In HttpServlet, it delegates requests to doGet, doPost, etc. • public void destroy(): • Called when server decides to terminate the serverlet. • Release resources. Dickson Chiu 2004

  15. Environment Installation • Visit: http://java.sun.com/j2ee/1.4/download.html • Download and install J2EE 1.4 / JEE5 at say: H:\Sun\AppServer\ • Start the default server from the program menu. • Download and extract the J2EE 1.4 examples update 2 (.zip file) under the same root: H:\Sun\AppServer\ • The main references text are inside:H:\Sun\AppServer\j2eetutorial14\doc • Very Important - edit the file: H:\Sun\AppServer\j2eetutorial14\examples\common\build.properties • set the first line: j2ee.home=H:/Sun/AppServer/ • Set the port if you have changed the default one • You may need a text editor (e.g. wordpad) other than notepad to convert UNIX file formats (line terminator problem) Dickson Chiu 2004

  16. Compiling hello2 • In a terminal window, go to H:/Sun/AppServer/j2eetutorial14/examples/web/hello2/ • Run asant build. This target will compile the servlets to the directory H:/Sun/AppServer/j2eetutorial14/examples/web/hello2/build/ • Double check if your environment path includes H:/Sun/AppServer/bin • asant is a build tool conceptually similar to makefile but modernize with XML  • See apache ant documentation too: http://ant.apache.org/ Dickson Chiu 2004

  17. For JEE5 • Edit the web.xml / sun-web.xml file if necessary • Create the .war file with: asant create-war • You may open it with Winzip or Winrar and you can add other files into it manually. • Deploy the .war • with the web-based admin tool • copy the .war to the auto-deploy directory • run: asant deploy-war Dickson Chiu 2004

  18. Creating the .WAR file and Descriptors • Start deploytool from the program menu • Create a Web application called hello2 by running the New Web Component wizard. • Select File->New->Web Component • In the New Web Component wizard: • Select the Create New Stand-Alone WAR Module radio button. • In the WAR Location field, enter H:/Sun/AppServer/j2eetutorial14/examples/web/hello2/hello2.war • In the WAR Name field, enter hello2 • In the Context Root field, enter /hello2 • Click Edit Contents to add the content files • In the Edit Contents dialog box, navigate to H:/Sun/AppServer/j2eetutorial14/examples/web/hello2/build/. • Select duke.waving.gif and the servlets package and click Add. Click OK. • Click Next. • Select the Servlet radio button. • Click Next. • Select GreetingServlet from the Servlet Class combo box. • Click Finish. Dickson Chiu 2004

  19. Configure the Second Servlet Select File New Web Component. • Click the Add to Existing WAR Module radio button and select hello2 from the combo box. Because the WAR contains all the servlet classes, you do not have to add any more content. • Click Next. • Select the Servlet radio button. • Click Next. • Select ResponseServlet from the Servlet Class combo box. • Click Finish. Dickson Chiu 2004

  20. Setting Aliases Before Running • Select the GreetingServlet Web component. • Select the Aliases tab. • Click Add to add a new mapping. • Type /greeting in the aliases list. • Select the ResponseServlet Web component. • Click Add. • Type /response in the aliases list. • Select File Save. • Deploy the Web moduleSelect the WAR file hello2 • Select from menu: tools -> deploy • You need the admin password • Running - open the URL in a browser: http://localhost:8080/hello2/greeting Dickson Chiu 2004

  21. Changing Your Program • Recompile with asant build • Command Line • Run: asant undeploy-war • Run: asant deploy-war • Use admin tool to redeploy • copy the .war to the auto-deploy directory • In the deploytool • Select hello2.war • Click edit content • Add the changed class files, overwriting the old one • Save changes • Deploy again Dickson Chiu 2004

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