（接上期）
Web tier当使用者输入http://localhost:8080/petstore/customer.do，MainServlet接收到Request，转到doProcess()函数：private void doProcess(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { // set the locale of the user to default if not set if (request.getSession().getAttribute(WebKeys.LOCALE) == null) { request.getSession().setAttribute(WebKeys.LOCALE, defaultLocale); } try { getRequestProcessor().processRequest(request);//进行转导动作(forward) getScreenFlowManager().forwardToNextScreen(request,response); } catch (Throwable ex) { String className = ex.getClass().getName(); String nextScreen = getScreenFlowManager().getExceptionScreen(ex); // put the exception in the request request.setAttribute("javax.servlet.jsp.jspException", ex); if (nextScreen == null) { // send to general error screen ex.printStackTrace(); throw new ServletException("MainServlet: unknown exception: " + className); } context.getRequestDispatcher(nextScreen).forward(request, response); }}请开启Petstore_home/src/waf/src/controller/com/sun/j2ee/blueprints/waf/controller/web/flow/ScreenFlowManager.java，在约112列可找到forwardToNextScreen()函数：public void forwardToNextScreen(HttpServletRequest request, HttpServletResponse response) throws java.io.IOException, FlowHandlerException,javax.servlet.ServletException { // set the presious screen String fullURL = request.getRequestURI(); // get the screen name String selectedURL = defaultScreen; int lastPathSeparator = fullURL.lastIndexOf("/") + 1; if (lastPathSeparator != -1) { selectedURL = fullURL.substring(lastPathSeparator, fullURL.length()); } //请加入侦察码，以本例来说，selectedURL=customer.do System.out.println("selectURL="+ selectedURL); String currentScreen = ""; URLMapping urlMapping = getURLMapping(selectedURL); if (urlMapping != null) { if (!urlMapping.useFlowHandler()) { currentScreen = urlMapping.getScreen(); //请加入侦察码，以本例来说，currentScreen =customer.screen System.out.println("currentScreen="+currentScreen); } else { // load the flow handler FlowHandler handler = null; String flowHandlerString = urlMapping.getFlowHandler(); try { handler = (FlowHandler)getClass().getClassLoader() .loadClass(flowHandlerString).newInstance(); // invoke the processFlow(HttpServletRequest) handler.doStart(request); String flowResult = handler.processFlow(request); handler.doEnd(request); currentScreen = urlMapping.getResultScreen(flowResult); // if there were no screens by the id then assume that the result was //the screen itself if (currentScreen == null) currentScreen = flowResult; } catch (Exception ex) { System.err.println("ScreenFlowManager caught loading handler: " + ex); } } } if (currentScreen == null) { System.err.println("ScreenFlowManager: Screen not found for " + selectedURL); throw new RuntimeException("Screen not found for " + selectedURL); } //进行转导动作(forward) System.out.println("forward to "+ currentScreen); context.getRequestDispatcher("/" + currentScreen).forward(request, response);}我们知道它会转导至customer.screen，从screendefinitions_en_US.xml，可找到对应各画面区块：<screen name="customer"> <parameter key="title" value="Customer" direct="true"/> <parameter key="banner" value="/banner.jsp" /> <parameter key="sidebar" value="/sidebar.jsp" /> <parameter key="body" value="/customer.jsp" /> <parameter key="mylist" value="/mylist.jsp" /> <parameter key="footer" value="/footer.jsp" /></screen>其实大部份与main.screen都相同，唯一差异部份就是主体区块(body)，开启customer.jsp瞧它的内容，位置在Petstore_home/src/apps/petstore/src/docroot，在约50列：<table cellpadding="5" cellspacing="0" width="100%" border="0"><tr><td colspan="3"><p class="petstore_title">Contact Information</p></td></tr><tr><td class="petstore_form" align="right"><b>First Name</b></td> <td class="petstore_form" align="left"colspan="2"><c:out value="${customer.account.contactInfo.givenName}"/></td></tr>以下略...以上程序代码作用要将使用者名称(First Name)显示出现，它利用JSTL Tags要资料打印出来，可是问题来了，资料是如何得来的？答案就是本文前头所提到的四个隐形角色之一－SignOnNotifier Attribute Listener。SignOnNotifier请读者回想前头所提，当使用者身分验证成功后，SignOnFilter会将SIGNED_ON_USER对应变量设定真值(true)，存入Session：hreq.getSession().setAttribute(SIGNED_ON_USER, new Boolean(true));此时便会触发SignOnNotifier，请开启：Petstore_home/src/apps/petstore/src/com/sun/j2ee/blueprints/petstore/controller/web/SignOnNotifier.java，在约89列：/** * Process an attribute added *属性新增后 */public void attributeAdded(HttpSessionBindingEvent se) { processEvent(se);}/** * Process the update *属性覆盖后 */public void attributeReplaced(HttpSessionBindingEvent se) { processEvent(se);}private void processEvent(HttpSessionBindingEvent se) { HttpSession session = se.getSession(); String name = se.getName(); /* check if the value matches the signon attribute * if a macth fire off an event to the ejb tier that the user * has signed on and load the account for the user */ //判别新增或覆盖属性为”SIGNED_ON_USER”则进行处理，否则略过 if (name.equals(SignOnFilter.SIGNED_ON_USER)) { boolean aSignOn = ((Boolean)se.getValue()).booleanValue(); if (aSignOn) { String userName = (String)session.getAttribute(SignOnFilter.USER_NAME);//请加入侦察码System.out.println("SignOnNotifier() userName="+userName); // look up the model manager and webclient controller PetstoreComponentManager sl = (PetstoreComponentManager)session.getAttribute(PetstoreKeys.COMPONENT_MANAGER); WebController wc = sl.getWebController(session); SignOnEvent soe = new SignOnEvent(userName); // set the EJBAction on the Event EventMapping em = getEventMapping(session.getServletContext(), soe); if (em != null) { soe.setEJBActionClassName(em.getEJBActionClassName());System.out.println("EJBActionClassName="+ em.getEJBActionClassName()); } try { //更新资料时会用到，以本例来说只需读取，所以没有作用 wc.handleEvent(soe, session); } catch (EventException e) { System.err.println("SignOnNotifier Error handling event " + e); } //取得Customer EJB Local Interface Reference CustomerLocal customer = sl.getCustomer(session); // ensure the customer object is put in the session //将Customer EJB Local Interface存入Session if (session.getAttribute(PetstoreKeys.CUSTOMER) == null) { session.setAttribute(PetstoreKeys.CUSTOMER, customer); } // set the language to the preferred language and other preferences ProfileLocal profile = sl.getCustomer(session).getProfile(); Locale locale = I18nUtil.getLocaleFromString(profile.getPreferredLanguage()); session.setAttribute(PetstoreKeys.LOCALE, locale); } }}以下略... SignOnNotifier会透过PetstoreComponentManager取得ShoppingClientFacade reference，ShoppingClientFacade是Petstore在EJB tier的代理接口，Web tier所有Request均需透过它来存取所需资料，这个Design Pattern的好处是可以降低EJB tier与Web tier间的藕合性，将商业逻辑集中控管在EJB tier。PetstoreComponentManager，源码在D:/petstore1.3.1/src/apps/petstore/src/com/sun/j2ee/blueprints/petstore/controller/web/ PetstoreComponentManager.java，约110列：public CustomerLocal getCustomer(HttpSession session) { ShoppingControllerLocal scEjb = getShoppingController(session); try { //取得ShoppingClientFacade reference ShoppingClientFacadeLocal scf = scEjb.getShoppingClientFacade(); //scf.setUserId(userId); //取得CustomerLocal reference return scf.getCustomer(); } catch (FinderException e) { System.err.println("PetstoreComponentManager finder error: " + e); } catch (Exception e) { System.err.println("PetstoreComponentManager error: " + e); } return null;}ShoppingClientFacadeLocalEJB为Session Bean，源码在D:/petstore1.3.1/src/apps/petstore/src/com/sun/j2ee/blueprints/petstore/controller/ejb/ ShoppingClientFacadeLocalEJB.java，约101列：/* * Asume that the customer userId has been set */public CustomerLocal getCustomer() throws FinderException { //请加入侦察码 System.out.println("ShoppingClientFacadeLocalEJB.getCustomer()"); if (userId == null) { throw new GeneralFailureException("ShoppingClientFacade: failed to look up name of customer: userId is not set" ); } try { ServiceLocator sl = new ServiceLocator(); CustomerLocalHome home =(CustomerLocalHome) sl.getLocalHome(JNDINames.CUSTOMER_EJBHOME); customer = home.findByPrimaryKey(userId); } catch (ServiceLocatorException slx) { throw new GeneralFailureException("ShoppingClientFacade: failed to look up name of customer: caught " + slx); } return customer;}CustomerEJB为Entity Bean，它与AccountEJB有一对一关系，AccountEJB也与ContactInfoEJB有一对一关系，三者皆为Entity Bean，直接对应资料库资料表CustomerEJBTable, AccountEJBTable, ContactInfoEJBTable，源码在D:/petstore1.3.1/src/components/customer/src/com/sun/j2ee/blueprints/customer/目录下，因Entity Bean无特别之处，故不再说明。图24 Entity Beans间的关系(Relation)所以<c:out value="${customer.account.contactInfo.givenName}"/>即是从Session取出CustomerLocal，再透过CMR字段(即前面所提关系)取得最底层givenName字段显示出来。将程序重新编译及部署，可得如下预期结果：图25 SignOnNotifier取得CustomerLocal结语笔者将整个使用者基本数据浏览流程做一总整理，绘制成合作图，帮助读者更容易了解：图25 使用者基本资料浏览合作图1.使用者进入首页。2.点选右上角Account连结(customer.do)，欲进入使用者基本资料浏览画面，Request中途被SignOnNotifier拦截。3.SignOnFilter读取signon-config.xml设定。4. SignOnFilter依据signon-config.xml设定，发现customer.do是受保护的资源，且使用者尚未进行登入动作，所以转导至signon.screen画面。5.使用者输入帐号及密码，按”Sumit”后，Request再度被SignOnFilter拦截，透过SignOnEJB Session Bean进行验证。6.SignOnEJB Session Bean透过UserEJB比对密码是否正确。7.密码验证无误后，会在Session写入使用者已登入标记，此时会触发SignOnNotifier。8.SignOnNotifier透过PetstoreComponentManager，PetstoreComponentManager是Petstore在Web tier的接口。SignOnNotifier经过后面9至13步骤取得CustomerEJB对应CustomerLocal，并存入Session。9.PetstoreComponentManager透过ShoppingControllerEJB，ShoppingControllerEJB是Petstore在EJB tier的接口。10.ShoppingControllerEJB透过ShoppingClientFacadeEJB，ShoppingClientFacadeEJB是Petstore在EJB tier关于前端购物所有功能统一提供接口。11.ShoppingClientFacadeEJB取得CustomerEJB Entity Bean，CustomerEJB代表CustomerEJBTable资料表。12.CustomerEJB Entity Bean对AccountEJB Entity Bean有一对一关系，AccountEJB代表AccountEJBTable资料表。13. AccountEJB Entity Bean对ContactInfoEJB Entity Bean有一对一关系，ContactInfoEJB代表ContactInfoEJBTable资料表。14.SignOnFilter在第7步骤验证无误后，则将Request(customer.do)放行。15.Request(customer.do)由MainServlet接收，MainServlet负责处理*.do的Request。16.MainServlet读取mappings.xml相关设定，找出customer.do所对应的web action class(在web tier欲执行工作，以本例来说，只有浏览，所以没有对应的工作)及screen(结果呈现画面)。17.MainServlet将screen交给ScreenFlowManager，它负责转导工作。18. screen对应值为customer.screen，所以转导至customer.screen。 写到这里笔者已经快昏了！第一次写这么长的文章，不过还是要强打精神做个Endding，由这三期探讨Petstore架构，一个完整的J2EE framework已然成形，在J2EE所提到的大部份技术几乎都用上了，也见到了各种技术该如何整合运用，这就是所谓的Design Pattern，也许读者会想这样的架构能不能直接套用在我们实际要开发的项目上？当然是可以，不过在Web tier的架构已有更完整、更套装化的framework出现，就是struts，网址在http://jakarta.apache.org/struts/index.html，它是Apache Jakarta下的一个子项目(Jakarta最有名的子项目就是Tomcat)，一个免费且会持续升级的framework，目前是当红炸子鸡，它整个架构与Petstore类似，只是它提的solution只在Web tier，笔者建议可运用struts来开发我们的项目，当我们已了解Petstore的架构，学习struts必能事半功倍，且能补上struts在EJB tier缺乏的framework。若读者有任何问题或意见欢迎与笔者讨论，E-Mail:senshaw@ms4.hinet.net。注1：Petstore_home代表您的Petstore安装目录。注2：deploytool的开启方式及将pestore.ear加载deploytool请参阅本系列第一篇文章。注3：DAO产生过程与本系列第二篇CatalogDAO产生方式相似，笔者不再赘述。注4：读者若想观察cloudscape数据库中相关资料表，笔者在此提供一个方法，可利用JBuilder之Database Pilot来观察：a.请开启JBuilder，点选menu bar之”Tools” > “Enterprise Setup”，请选择”Database Drivers”页，按”add”钮，请新增一个library将cloudscape相关jar文件，位置在j2ee安装目录/lib/cloudscape下三个档案选进来后按”ok”钮，此时JBuilder会要求您重新激活JBuiler，将JBuilder关闭。b.开启Database Pilot，点选menu bar之”File” > “New”，会出现一窗口要您输入Driver及URL，请依下列值输入：Driver:COM.cloudscape.core.RmiJdbcDriverURL:jdbc:cloudscape:rmi:PetStoreDB;create=truec.点选左半边增加出来的URL，点选两下会要求您输入username及password，直接略过按”ok”，会发现所有资料表都出现啦！d.Database Pilot详细操作请参考JBuiler相关文件。与作者联络： senshaw@ms4.hinet.net
