一個(gè)請求在Struts2框架中的處理大概分為以下幾個(gè)步驟：客戶端提起一個(gè)（HttpServletRequest）請求,如上文在瀏覽器中輸入”http://localhost:8080/TestMvc/add.action”就是提起一個(gè)（HttpServletRequest）請求。請求被提交到一系列（主要是三層）的過濾器（Filter），如（ActionContextCleanUp、其他過濾器（SiteMesh等）、 FilterDispatcher）。注意這里是有順序的，先ActionContextCleanUp，再其他過濾器（SiteMesh等）、最后到FilterDispatcher。FilterDispatcher是控制器的核心，就是mvc中c控制層的核心。下面粗略的分析下我理解的FilterDispatcher工作流程和原理：FilterDispatcher進(jìn)行初始化并啟用核心doFilter其代碼如下：public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException ...{ HttpServletRequest request = (HttpServletRequest) req; HttpServletResponse response = (HttpServletResponse) res; ServletContext servletContext = filterConfig.getServletContext(); // 在這里處理了HttpServletRequest和HttpServletResponse。 DispatcherUtils du = DispatcherUtils.getInstance(); du.PRepare(request, response);//正如這個(gè)方法名字一樣進(jìn)行l(wèi)ocale、encoding以及特殊request parameters設(shè)置 try ...{ request = du.wrapRequest(request, servletContext);//對request進(jìn)行包裝 } catch (IOException e) ...{ String message = "Could not wrap servlet request with MultipartRequestWrapper!"; LOG.error(message, e); throw new ServletException(message, e); } ActionMapperIF mapper = ActionMapperFactory.getMapper();//得到action的mapper ActionMapping mapping = mapper.getMapping(request);// 得到action 的 mapping if (mapping == null) ...{ // there is no action in this request, should we look for a static resource? String resourcePath = RequestUtils.getServletPath(request); if ("".equals(resourcePath) && null != request.getPathInfo()) ...{ resourcePath = request.getPathInfo(); } if ("true".equals(Configuration.get(WebWorkConstants.WEBWORK_SERVE_STATIC_CONTENT)) && resourcePath.startsWith("/webwork")) ...{ String name = resourcePath.substring("/webwork".length()); findStaticResource(name, response); } else ...{ // this is a normal request, let it pass through chain.doFilter(request, response); } // WW did its job here return; } Object o = null; try ...{ //setupContainer(request); o = beforeActionInvocation(request, servletContext);//整個(gè)框架最最核心的方法，下面分析 du.serviceAction(request, response, servletContext, mapping); } finally ...{ afterActionInvocation(request, servletContext, o); ActionContext.setContext(null); } }du.serviceAction(request, response, servletContext, mapping);//這個(gè)方法詢問ActionMapper是否需要調(diào)用某個(gè)Action來處理這個(gè)（request）請求，如果ActionMapper決定需要調(diào)用某個(gè)Action，F(xiàn)ilterDispatcher把請求的處理交給ActionProxypublic void serviceAction(HttpServletRequest request, HttpServletResponse response, String namespace, String actionName, Map requestMap, Map parameterMap, Map sessionMap, Map applicationMap) ...{ HashMap extraContext = createContextMap(requestMap, parameterMap, sessionMap, applicationMap, request, response, getServletConfig()); //實(shí)例化Map請求 ，詢問ActionMapper是否需要調(diào)用某個(gè)Action來處理這個(gè)（request）請求 extraContext.put(SERVLET_DISPATCHER, this); OgnlValueStack stack = (OgnlValueStack) request.getAttribute(ServletActionContext.WEBWORK_VALUESTACK_KEY); if (stack != null) ...{ extraContext.put(ActionContext.VALUE_STACK,new OgnlValueStack(stack)); } try ...{ ActionProxy proxy = ActionProxyFactory.getFactory().createActionProxy(namespace, actionName, extraContext); //這里actionName是通過兩道getActionName解析出來的, FilterDispatcher把請求的處理交給ActionProxy，下面是ServletDispatcher的 TODO: request.setAttribute(ServletActionContext.WEBWORK_VALUESTACK_KEY, proxy.getInvocation().getStack()); proxy.execute(); //通過代理模式執(zhí)行ActionProxy if (stack != null)...{ request.setAttribute(ServletActionContext.WEBWORK_VALUESTACK_KEY,stack); } } catch (ConfigurationException e) ...{ log.error("Could not find action", e); sendError(request, response, HttpServletResponse.SC_NOT_FOUND, e); } catch (Exception e) ...{ log.error("Could not execute action", e); sendError(request, response, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e); } } FilterDispatcher詢問ActionMapper是否需要調(diào)用某個(gè)Action來處理這個(gè)（request）請求，如果ActionMapper決定需要調(diào)用某個(gè)Action，F(xiàn)ilterDispatcher把請求的處理交給ActionProxy。ActionProxy通過Configuration Manager（struts.xml）詢問框架的配置文件，找到需要調(diào)用的Action類.如上文的struts.xml配置<?xml version="1.0" encoding="GBK"?> <!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN" "http://struts.apache.org/dtds/struts-2.0.dtd"> <struts> <include file="struts-default.xml"/> <package name="struts2" extends="struts-default"> <action name="add" class="edisundong.AddAction" > <result>add.jsp</result> </action> </package> </struts>如果提交請求的是add.action，那么找到的Action類就是edisundong.AddAction。 ActionProxy創(chuàng)建一個(gè)ActionInvocation的實(shí)例，同時(shí)ActionInvocation通過代理模式調(diào)用Action。但在調(diào)用之前ActionInvocation會(huì)根據(jù)配置加載Action相關(guān)的所有Interceptor。（Interceptor是struts2另一個(gè)核心級的概念）下面我們來看看ActionInvocation是如何工作的：ActionInvocation 是Xworks 中Action 調(diào)度的核心。而對Interceptor 的調(diào)度，也正是由ActionInvocation負(fù)責(zé)。ActionInvocation 是一個(gè)接口， 而DefaultActionInvocation 則是Webwork 對ActionInvocation的默認(rèn)實(shí)現(xiàn)。Interceptor 的調(diào)度流程大致如下：1. ActionInvocation初始化時(shí)，根據(jù)配置，加載Action相關(guān)的所有Interceptor。2. 通過ActionInvocation.invoke方法調(diào)用Action實(shí)現(xiàn)時(shí)，執(zhí)行Interceptor。Interceptor將很多功能從我們的Action中獨(dú)立出來，大量減少了我們Action的代碼，獨(dú)立出來的行為具有很好的重用性。XWork、WebWork的許多功能都是有Interceptor實(shí)現(xiàn)，可以在配置文件中組裝Action用到的Interceptor，它會(huì)按照你指定的順序，在Action執(zhí)行前后運(yùn)行。那么什么是攔截器。攔截器就是AOP（aspect-Oriented Programming）的一種實(shí)現(xiàn)。（AOP是指用于在某個(gè)方法或字段被訪問之前，進(jìn)行攔截然后在之前或之后加入某些操作。）攔截器的例子這里就不展開了。struts-default.xml文件摘取的內(nèi)容：< interceptor name ="alias" class ="com.opensymphony.xwork2.interceptor.AliasInterceptor" /> < interceptor name ="autowiring" class ="com.opensymphony.xwork2.spring.interceptor.ActionAutowiringInterceptor" /> < interceptor name ="chain" class ="com.opensymphony.xwork2.interceptor.ChainingInterceptor" /> < interceptor name ="conversionError" class ="org.apache.struts2.interceptor.StrutsConversionErrorInterceptor" /> < interceptor name ="createSession" class ="org.apache.struts2.interceptor.CreateSessionInterceptor" /> < interceptor name ="debugging" class ="org.apache.struts2.interceptor.debugging.DebuggingInterceptor" /> < interceptor name ="external-ref" class ="com.opensymphony.xwork2.interceptor.ExternalReferencesInterceptor" /> < interceptor name ="execAndWait" class ="org.apache.struts2.interceptor.ExecuteAndWaitInterceptor" /> < interceptor name ="exception" class ="com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor" /> < interceptor name ="fileUpload" class ="org.apache.struts2.interceptor.FileUploadInterceptor" /> < interceptor name ="i18n" class ="com.opensymphony.xwork2.interceptor.I18nInterceptor" /> < interceptor name ="logger" class ="com.opensymphony.xwork2.interceptor.LoggingInterceptor" /> < interceptor name ="model-driven" class ="com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor" /> < interceptor name ="scoped-model-driven" class ="com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor" /> < interceptor name ="params" class ="com.opensymphony.xwork2.interceptor.ParametersInterceptor" /> < interceptor name ="prepare" class ="com.opensymphony.xwork2.interceptor.PrepareInterceptor" /> < interceptor name ="static-params" class ="com.opensymphony.xwork2.interceptor.StaticParametersInterceptor" /> < interceptor name ="scope" class ="org.apache.struts2.interceptor.ScopeInterceptor" /> < interceptor name ="servlet-config" class ="org.apache.struts2.interceptor.ServletConfigInterceptor" /> < interceptor name ="sessionAutowiring" class ="org.apache.struts2.spring.interceptor.SessionContextAutowiringInterceptor" /> < interceptor name ="timer" class ="com.opensymphony.xwork2.interceptor.TimerInterceptor" /> < interceptor name ="token" class ="org.apache.struts2.interceptor.TokenInterceptor" /> < interceptor name ="token-session" class ="org.apache.struts2.interceptor.TokenSessionStoreInterceptor" /> < interceptor name ="validation" class ="com.opensymphony.xwork2.validator.ValidationInterceptor" /> < interceptor name ="workflow" class ="com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor" /> < interceptor name ="store" class ="org.apache.struts2.interceptor.MessageStoreInterceptor" /> < interceptor name ="checkbox" class ="org.apache.struts2.interceptor.CheckboxInterceptor" /> < interceptor name ="profiling" class ="org.apache.struts2.interceptor.ProfilingActivationInterceptor" /> 一旦Action執(zhí)行完畢，ActionInvocation負(fù)責(zé)根據(jù)struts.xml中的配置找到對應(yīng)的返回結(jié)果。如上文中將結(jié)構(gòu)返回“add.jsp”，但大部分時(shí)候都是返回另外一個(gè)action，那么流程又得走一遍………總結(jié)：
Struts2的工作流就只有這7步，比起Struts1簡單了很多（本人能力有限，struts2更多的東西現(xiàn)在還看不明白）。網(wǎng)上有很多很多的關(guān)于.net和java的比較之類的文章，可是有幾個(gè)作者是真正用過java和.net的呢？更多的評論都是人云亦云，想當(dāng)然的評論java和.net。作為技術(shù)人千萬不要屁股決定腦袋，關(guān)于web的設(shè)計(jì)模式上.net也不是那么一無是處，java也不是那么完美無缺。下一篇分析下asp.net的設(shè)計(jì)模式(生命周期)。
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