An Introduction To Java Enterprise Edition - انجمن جاواکاپ

JavaServer Faces A user interface framework for building web applicationsJavaServer Faces Components A GUI component framework A set of custom markup tags h:form , h:head A flexible model for rendering components in different kindsof HTML or different markup 51A Renderer object generates the markup to render the component &view its dataA standard RenderKit for generating HTML/4.01Sadegh AliakbaryJavaEE

JavaServer Faces Components Backing beans The logic of application Facelet The view of application Java classes using Java EE beansXHTML file using component tagsApplication configuration & description 52Mapping between Facelets & BeansFile organization, Sadegh AliakbaryJavaEE

EJB EJBs are distributed components used to implementbusiness logic (no UI)Developer concentrates on business logic Availability, scalability, security, interoperability and handled by the J2EE serverClient of EJBs can be JSPs, servlets, other EJBs andexternal applicationsClients see interfaces53Sadegh AliakbaryJavaEE

EJB Types Session Beans Entity Beans Synchronous Action: Process oriented service providersExample: Credit AuthorizationData: Represent dataExample: Customer, AccountMessage-Driven 54Asynchronous Action: Never called directly, only receivemessagesJMSExample: Transaction loggingSadegh AliakbaryJavaEE

Java EE Summary56Sadegh AliakbaryJavaEE

MVC What is design pattern? Designing complex SW system is really difficultDesign patterns help us to design in methodological mannerModel-View-Controller (MVC) 57Model Contains data, system state, and logicView Presents data and system stateController Handles events/requests affecting model or viewSadegh AliakbaryJavaEE

MVC?!58Sadegh AliakbaryJavaEE

MVC Interactions (cont’d)modelcontroller updatesmodelview queries modelmodel signals changesviewcontroller updatesviewcontrollereventevent is passed to the controller59Sadegh AliakbaryJavaEE

MVC in Web Applications Model consists of data and system stateDatabase tables Persistent dataCurrent system state dataBusiness logic (eCommerce) 60Rules governing the transactionSadegh AliakbaryJavaEE

MVC in Web Applications (cont’d) View gives a presentation of the modelClient-side presentation in a browser window (D)HTMLCSS style-sheetsServer-side templatesAdministrative information 61Server output logsSadegh AliakbaryJavaEE

MVC in Web Applications (cont’d) Controller handles eventsUser-generated events Client-side scriptingHTTP request processingRedirectionPre-processing62Sadegh Aliakbary JavaEE

MVC in Java EE: Approach 1 The pure JSP approachSeparate JSP pages are used for the controller andthe viewBeans being used for the model partThis is a good approach when the development isheavy in graphic designers and light in JavaprogrammersRelatively complex applications can be constructedwith the use of only JSP 63Is also well suited for prototyping Web applicationsSadegh AliakbaryJavaEE

MVC in Java EE: Approach 2 A combination of servlets, JSP, and beansA servlet accepts requests and implementbusiness logic The servlet that receives requests can use other servletsto handle various kinds of requestsBeans store and perform basic data manipulationJSP implements the user views of results ofrequestsConclude: Use servlets to implement the controller JSP to implement the view64Sadegh AliakbaryJavaEE

Application Server vs. Servlet Container A servlet-container supports only the servlet API including JSP, JSTLe.g. Apache TomcatAn application server supports the whole JavaEE 65EJB, JMS, JTA, Servlets, etc.E.g. JBossSadegh AliakbaryJavaEE

Servlet Containers Apache Tomcat Jetty 66Eclipse foundationSadegh AliakbaryJavaEE

Application Servers Apache Geronimo JBoss BEA OracleGlassGish An embedded Apache TomcatJBoss, Red HatWebLogic Tomcat or Jetty as the servlet containerSun OracleThe reference implementation of Java EEA derivative of Apache Tomcat as the servlet containerWebsphere 67IBMSadegh AliakbaryJavaEE

Oracle, BEA, Sun, 68Sadegh AliakbaryJavaEE

A closer look at JSP and Servlet(more practical)69Sadegh AliakbaryJavaEE

JSP Scripting Elements There are four types of scripting elements defined 70DeclarationExpressionScriptletsCommentsSadegh AliakbaryJavaEE

DeclarationDeclares a variable or method valid in the scripting languageused in the JSP pageJSP Syntax %! declaration; [ declaration; ] . % Examples %! int i 0; % %! int a, b, c; % %! Circle a new Circle(2.0); % 71Sadegh AliakbaryJavaEE

ExpressionJSP Syntax % expression % DescriptionAn expression that is converted to a StringExampleWelcome, % userName% Output:Welcome, James72Sadegh AliakbaryJavaEE

Expression % new java.util.Date()% The resulting servlet code will probably look like this:out.print(new java.util.Date());73Sadegh AliakbaryJavaEE

Script lets Contains a code fragment valid in the page scripting languageScriptlets allows you to include a series of java statementsyou must terminate them with semicolon.JSP Syntax % code fragment % 74Sadegh AliakbaryJavaEE

Scriptlets Examples % String name null;if (request.getParameter("name") null) { % %@ include file "error.html" % % }else }% 75Sadegh AliakbaryJavaEE

CommentsTo denote any lines you want to be completely ignored bythe JSP translation process.Example %-- Author: James Gosling --% 76Sadegh AliakbaryJavaEE

taglib directive The taglib directiveDeclares that the JSP page uses custom tagsNames the tag library that defines themand specifies their tag prefix.Defines a tag library and prefix for the custom tags used in the JSPpage.JSP Syntax %@ taglib {uri "URI" tagdir "/WEB-INF/tags[/subdir] "}prefix "tagPrefix" % Examples %@ taglib uri "http://www.jspcentral.com/tags" prefix "public" % public:loop 77. /public:loop Sadegh AliakbaryJavaEE

JSP Implicit objects Implicit objects are being created by JSP mechanismautomatically.They are accessible from the JSP pages :request – represents the HTTP request, which is beingserviced by the JSP page; it is an instance of a class,implementing javax.servlet.http.httpServletRequest interface; getParameter (only strings)getAttribute & setAttribute (any objects)response – represents the HTTP response, receiving by theJSP page; it is an instance of a class, implementingjavax.servlet.http.httpServletResponse interface;78Sadegh AliakbaryJavaEE

JSP Implicit objects (cont.) session – an instance of javax.servlet.http.HttpSession,representint an HTTP session; getAttribute & setAttribute (any objects)application – represents the servlet context for the Webapplication; it is instance of javax.servlet.ServletContextclass; getAttribute & setAttribute (any objects)out – instance of javax.servlet.jsp.JspWriter class, which isbeing used to write content in the JSP output;79Sadegh AliakbaryJavaEE

Example %Integer userviews views null)userviews 0;session.setAttribute("userviews", userviews);% HTML BODY Number of User Views: % userviews% /BODY /HTML 80Sadegh AliakbaryJavaEE

Example %Integer usersview usersview null)usersview 0;application.setAttribute("usersview", usersview);% HTML BODY Number of Users Views: % usersview% /BODY /HTML 81Sadegh AliakbaryJavaEE

Example %request.setAttribute("result",new Double(5.5));% 3.jsp jsp:forward page "display.jsp" / %display.jspDouble number (Double)request.getAttribute("result");String param request.getParameter("query");% HTML BODY Computed Result: % number% Query Parameter: % param% /BODY /HTML Entering:http://localhost:8080/app1/3.jsp?query salaResults:82Sadegh AliakbaryJavaEE

Example %request.setAttribute("result",new 4.jsp% %display.jspDouble number (Double)request.getAttribute("result");String param request.getParameter("query");% HTML BODY Computed Result: % number% Query Parameter: % param% /BODY /HTML Entering:http://localhost:8080/app1/4.jsp?query salaResults:83Sadegh AliakbaryJavaEE

New Presentation-layer Technologies Nowadays, enterprise applications usually use othertechnologies in presentation layerJSF, GWT, Wicket, SpringMVC, Vaadin, But we should know the architecture of JSP/ServletsMany technologies are built on servletServlet concepts are still important and useful84Sadegh AliakbaryJavaEE

Exercise Write a simple JSP fileDeploy it on TomcatSee how it worksSee the translated ServletSee the tomcat folders and files85Sadegh AliakbaryJavaEE

Review some concepts Request/Response t.setAttribute() Session/Application (ServletContext) Why?!Forwarding requestsShare 86Sadegh AliakbaryJavaEE

Getting Information FromRequestsParameters used to convey information between clients andservletsString bookId request.getParameter("Add");Object-valued attributes 87used to pass information between the servlet containerand a servlet or between collaborating bject identifier request.getAttribute(“id”);Sadegh AliakbaryJavaEE

Getting Information FromRequests (cont)Information aboutthe protocolThe method (get, put, )Request pathHeadersQuery String 88Sadegh AliakbaryJavaEE

Constructing ResponsesIndicate the content type response.setContentType("text/html");Indicate whether to buffer output By default, any content written to the output stream is immediatelysent to the clientresponse.setBufferSize(8192);Retrieve an output stream To send character data, use the PrintWriter returned by theresponse's getWriter methodTo send binary data in a MIME body response, use theServletOutputStream returned by getOutputStreamUsing Output stream 89output.println(" html “);Sadegh AliakbaryJavaEE

Invoking Other Web ResourcesTo invoke a resource available on the server that isrunning a web component, you must first obtain aRequestDispatcher using thegetRequestDispatcher("URL") methodTo include another resource, invoke the includemethod of a RequestDispatcher: include(request, response);To forward to another resource, invoke the forward: 90forward(request, response);Sadegh AliakbaryJavaEE

Example: Transferring Control toAnother Web Componentpublic class Dispatcher extends HttpServlet {public void doGet(HttpServletRequest request,HttpServletResponse response) {.request.setAttribute("avg", new Double(18.5));RequestDispatcher dispatcher request.getRequestDispatcher("/template.jsp");if (dispatcher ! null)dispatcher.forward(request, response);}public void doPost(HttpServletRequest request,.}91Sadegh AliakbaryJavaEE

Web ContextThe application object in JSP is called theServletContext object in a servletThe context in which web components execute is anobject that implements the ServletContext interfaceWe can retrieve the web context with thegetServletContext() methodpublic class MyServlet extends HttpServlet{private ServletContext ctx null;@Overridepublic void init(ServletConfig config) throws ServletException {ctx config.getServletContext();} 92Sadegh AliakbaryJavaEE

Session: Maintaining Client StateSessions are represented by an HttpSession objectYou can access a session by calling the getSession()method of a request objectHttpSession session , obj);93Sadegh AliakbaryJavaEE

Servlet Container Folder Structure bin conf startupserver.xmlliblogstempwebappswork94War filesSadegh AliakbaryJavaEE

A web-app Structure Html, css, js, JSPsWEB-INF 95web.xmlclasseslibSadegh AliakbaryJavaEE

web.xml An xml fileContains 96Servlet definitionsServlet-mappingsFilter definitionsFilter-mappingsError-pages Sadegh AliakbaryJavaEE

web.xml servlet97Sadegh AliakbaryJavaEE

web.xml servlet-mapping98Sadegh AliakbaryJavaEE

web.xml error pages 99Sadegh Aliakbary200 OK401 Unauthorized403 Forbidden404 Not FoundJavaEE

Import in JSP Import in Java Import classes: includes the mentioned class in theprogramExample: import java.util.ArrayList;import java.sql.Connection;Import in JSP: %@ page import “CLASS NAME" % Example: 100 %@ page import "java.util.List" % Sadegh AliakbaryJavaEE

Filter Acts as preprocessor to request/response for targetservletExtracts common scenario among different servletsApplications? Authentication 101SSOStatisticsLog Sadegh AliakbaryJavaEE

web.xml filter102Sadegh AliakbaryJavaEE

Filter Servlets HttpPageAuthenticateFilterServlet erifyDataServletSadegh AliakbaryJavaEE

Filter ServletImport java.io.*;import javax.servlet.*;import javax.servlet.http.*;publc class PageHits extends HttpServlet implements Filter{private FilterConfig filterConfig null;implementFilter Interfacepublic void init(FilterConfig filterConfig) throws ServletException{this.filterConfig filterConfig;}public void destroy({this.filterConfig null;}104override init. methodoverride destroy methodSadegh AliakbaryJavaEE

Filter Servlet (cont.)public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException{if (filterConfig null)return;Must overridedoFilter methodInteger counter (Integer) nter");if (counter null)counter new Integer(0);counter new Integer(counter.intValue() 1);filterConfig.getServletContext().log("Number of hits is " bute("Counter", counter);chain.doFilter(req, resp)}105Sadegh AliakbaryJavaEE

Modify Deployment Descriptor web-app filter filter-name PageHits /filter-name filter-class ir.ac.sbu.PageHits /filter-class /filter filter-mapping filter-name PageHits /filter-name url-pattern /payment/* /url-pattern /filter-mapping /web-app 106Sadegh AliakbaryJavaEE

Listener Servlet Servlet is automatically executed whensome external event occursEvent ListenersHTTPSessionActivationListenerSession is ssion attribute is added/removedHTTPSessionListenerSession attribute is rvlet contextattribute isadded/removedServletContextListenerServlet context changes107Sadegh AliakbaryJavaEE

What Events to Listen? ServletContextListener HttpSessionListener vletRequestAttributeListener Listener buteListener Sadegh AliakbaryJavaEE

Examplepublic class MyListener onEvent p) {}sessionWillPassivate(HttpSessionEvent p) {}attributeAdded(HttpSessionBindingEvent p) {}attributeRemoved(HttpSessionBindingEvent p) {}attributeReplaced(HttpSessionBindingEvent p) {}sessionCreated(HttpSessionEvent p) {}sessionDestroyed(HttpSessionEvent p) {}}109Sadegh AliakbaryJavaEE

Create Listener ServletImport java.io.*;import javax.servlet.*;import javax.servlet.http.*;publc class Listener extends HttpServlet implements ServletContextListener{private ServletContext context null;Must implementListner Interfacepublic void contextIntialized(ServletContextEvent event){context event.getServerContext();Integer counter new Integer(0);context.setAttribute(“Counter”, counter);context.log(“Created Counter”);Must overridecontextInitializedmethod}public void contextDestroyed(ServletContextEvent ��Counter”);Must overridecontextDestroyedmethod}}110Sadegh AliakbaryJavaEE

web-app servlet /servlet servlet-mapping /servlet-mapping filter Web.xml /filter filter-mapping /filter-mapping listener listener-class Listener / listener -class /listener /web-app 111Sadegh AliakbaryJavaEE

Modify Filter Servletpublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException{if (filterConfig null)return;synchronized (this){Integer counter ( Integer) ounter”);if (counter null)No longer neededcounter new Integer(1);counter new Integer(counter.intValue() 1);filterConfig.getServletContext().log(“Number of hits is “ bute(“Counter”, counter); counter);}chain.doFilter(request, response);}}112Sadegh AliakbaryJavaEE

Modified Filter Servletpublic void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException{if (filterConfig null)return;synchronized (this){Integer counter ( Integer) ounter”);counter new Integer(counter.intValue() 1);filterConfig.getServletContext().log(“Number of hits is “ bute(“Counter”, counter); counter);}chain.doFilter(request, response);}}113Sad

Java EE Java Platforms Java Card: Smart card version Java ME (Micro Edition): Embedded systems, e.g. Mobile handheld Java SE (Standard Edition): Desktop application development Java EE (Enterprise Edition): Enterprise distributed application software Java EE add standards and libraries to SE for fault- tolerant, distributed, multi-tier based components