| ? | 刚接触SpringMVC,对它的xml文件配置一直比较模模糊糊，最近花了一点时间稍微看了下源代码，再加上调试，开始逐渐理解它，网上的类似的内容有很多，写本文主要是自己加深一下理解。本文适合用过SpringMVC的开发者，言归正传，首先搭建一个最简单的工程体验一下。?
该工程是基于maven的，pom配置不再说明，所使用的spring版本4.0.5。?
首先是web.xml文件配置，最简单的配置?
Java代码?? <!DOCTYPE?web-app?PUBLIC?? ?"-//Sun?Microsystems,?Inc.//DTD?Web?Application?2.3//EN"?? ?"http://java.sun.com/dtd/web-app_2_3.dtd"?>?? ?? <web-app>?? ??<display-name>Archetype?Created?Web?Application</display-name>?? ??<servlet>?? ????????<servlet-name>mvc</servlet-name>?? ????????<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>?? ????????<load-on-startup>1</load-on-startup>?? ????</servlet>?? ?? ????<servlet-mapping>?? ????????<servlet-name>mvc</servlet-name>?? ????????<url-pattern>/*</url-pattern>?? ????</servlet-mapping>?? </web-app>??
然后是mvc-servlet.xml文件的配置，上面配置DispatcherServlet会默认加载[servlet-name]-servlet.xml文件。对于我的配置，会去加载mvc-servlet.xml文件。?
mvc-servlet.xml文件的内容：?
Java代码?? <?xml?version="1.0"?encoding="UTF-8"??>?? <beans?xmlns="http://www.springframework.org/schema/beans"?xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"?xmlns:mvc="http://www.springframework.org/schema/mvc"?xmlns:util="http://www.springframework.org/schema/util"?xmlns:context="http://www.springframework.org/schema/context"?? ????xsi:schemaLocation="http://www.springframework.org/schema/beans?? ????http://www.springframework.org/schema/beans/spring-beans-3.1.xsd?? ????http://www.springframework.org/schema/mvc?? ????http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd?? ????http://www.springframework.org/schema/util?? ????http://www.springframework.org/schema/util/spring-util-2.0.xsd?? ????http://www.springframework.org/schema/context??? ????http://www.springframework.org/schema/context/spring-context-3.2.xsd">?? ?? ????<bean?name="/index"?class="com.lg.mvc.HomeAction"></bean>?? ????<bean?class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">?? ????????<property?name="templateLoaderPath"?value="/WEB-INF/views"?/>?? ????????<property?name="defaultEncoding"?value="utf-8"?/>?? ????????<property?name="freemarkerSettings">?? ????????????<props>?? ????????????????<prop?key="locale">zh_CN</prop>?? ????????????</props>?? ????????</property>?? ????</bean>?? ????<bean?class="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">?? ????????<property?name="suffix"?value=".html"?/>?? ????????<property?name="contentType"?value="text/html;charset=utf-8"?/>?? ????????<property?name="requestContextAttribute"?value="request"?/>?? ????????<property?name="exposeRequestAttributes"?value="true"?/>?? ????????<property?name="exposeSessionAttributes"?value="true"?/>?? ????</bean>?? </beans>??
在该配置中定义了一个HomeAction的Bean。内容为：?
Java代码?? package?com.lg.mvc;?? ?? import?javax.servlet.http.HttpServletRequest;?? import?javax.servlet.http.HttpServletResponse;?? ?? import?org.springframework.web.servlet.ModelAndView;?? import?org.springframework.web.servlet.mvc.Controller;?? ?? public?class?HomeAction?implements?Controller{?? ?? [email protected] ????public?ModelAndView?handleRequest(HttpServletRequest?request,?? ????????????HttpServletResponse?response)?throws?Exception?{?? ????????return?new?ModelAndView("hello");?? ????}?? }??
这是最原始的mvc做法，要继承Controller接口，先从原始的说起，[email protected]@[email protected]??配置有一个关键的属性name="/index"。?
WEB-INF/view目录下有一个简单的hello.html，内容为：?
Java代码?? <html>?? ????<head>?? ?????? ????</head>?? ????<body>?? ????????hello?lg?!?? ????</body>?? </html>??
至此该工程就写完了，部署到tomcat中，项目路径为/,运行一下。?
访问 http://localhost:8080/index?
 ?
至此整个工程就算搭建成功了。?
下面就要说说原理了。?
用过python Django框架的都知道Django对于访问方式的配置就是，一个url路径和一个函数配对，你访问这个url，就会直接调用这个函数，简单明了。对于java的面向对象来说，就要分两步走。第一步首先要找到是哪个对象，即handler，本工程的handler则是HomeAction对象。第二步要找到访问的函数，即HomeAction的handleRequest方法。所以就出现了两个源码接口 HandlerMapping和HandlerAdapter，前者负责第一步，后者负责第二步。借用网上的SpringMVC架构图。?
HandlerMapping接口的实现（只举了我认识的几个） ：?
HandlerAdapter 接口实现：?
先简单的说下这个工程的流程，访问http://localhost:8080/index首先由DispatcherServlet进行转发，通过BeanNameUrlHandlerMapping(含有 /index->HomeAction的配置)，找到了HomeAction,然后再拿HomeAction和每个adapter进行适配，由于HomeAction实现了Controller接口，所以最终会有SimpleControllerHandlerAdapter来完成对HomeAction的handleRequest方法的调度。然后就顺利的执行了我们想要的方法，后面的内容不在本节中说明。?
了解了大概流程，然后就需要看源代码了。?
首先就是SpringMVC的入口类，DispatcherServlet，它实现了Servlet接口，不再详细说DispatcherServlet的细节，不然又是一大堆的内容。每次请求都会调用它的doService->doDispatch，我们关注的重点就在doDispatch方法中。?
Java代码?? protected?void?doDispatch(HttpServletRequest?request,?HttpServletResponse?response)?throws?Exception?{?? ????????HttpServletRequest?processedRequest?=?request;?? ????????HandlerExecutionChain?mappedHandler?=?null;?? ????????boolean?multipartRequestParsed?=?false;?? ?? ????????WebAsyncManager?asyncManager?=?WebAsyncUtils.getAsyncManager(request);?? ?? ????????try?{?? ????????????ModelAndView?mv?=?null;?? ????????????Exception?dispatchException?=?null;?? ?? ????????????try?{?? ????????????????processedRequest?=?checkMultipart(request);?? ????????????????multipartRequestParsed?=?(processedRequest?!=?request);?? ??????????????????????//这个是重点，第一步由HandlerMapping找到对应的handler?? ????????????????//?Determine?handler?for?the?current?request.?? ????????????????mappedHandler?=?getHandler(processedRequest);?? ????????????????if?(mappedHandler?==?null?||?mappedHandler.getHandler()?==?null)?{?? ????????????????????noHandlerFound(processedRequest,?response);?? ????????????????????return;?? ????????????????}?? ?? ????????????????//?Determine?handler?adapter?for?the?current?request.?? ???????????????????????//这是第二步，找到合适的HandlerAdapter，然后由它来调度执行handler的方法?? ????????????????HandlerAdapter?ha?=?getHandlerAdapter(mappedHandler.getHandler());?? ?? ????????????????//?Process?last-modified?header,?if?supported?by?the?handler.?? ????????????????String?method?=?request.getMethod();?? ????????????????boolean?isGet?=?"GET".equals(method);?? ????????????????if?(isGet?||?"HEAD".equals(method))?{?? ????????????????????long?lastModified?=?ha.getLastModified(request,?mappedHandler.getHandler());?? ????????????????????if?(logger.isDebugEnabled())?{?? ????????????????????????logger.debug("Last-Modified?value?for?["?+?getRequestUri(request)?+?"]?is:?"?+?lastModified);?? ????????????????????}?? ????????????????????if?(new?ServletWebRequest(request,?response).checkNotModified(lastModified)?&&?isGet)?{?? ????????????????????????return;?? ????????????????????}?? ????????????????}?? ?? ????????????????if?(!mappedHandler.applyPreHandle(processedRequest,?response))?{?? ????????????????????return;?? ????????????????}?? ?? ????????????????try?{?? ????????????????????//?Actually?invoke?the?handler.?? ????????????????????mv?=?ha.handle(processedRequest,?response,?mappedHandler.getHandler());?? ????????????????}?? ????????????????finally?{?? ????????????????????if?(asyncManager.isConcurrentHandlingStarted())?{?? ????????????????????????return;?? ????????????????????}?? ????????????????}?? ?? ????????????????applyDefaultViewName(request,?mv);?? ????????????????mappedHandler.applyPostHandle(processedRequest,?response,?mv);?? ????????????}?? ????????????catch?(Exception?ex)?{?? ????????????????dispatchException?=?ex;?? ????????????}?? ????????????processDispatchResult(processedRequest,?response,?mappedHandler,?mv,?dispatchException);?? ????????}?? ????????catch?(Exception?ex)?{?? ????????????triggerAfterCompletion(processedRequest,?response,?mappedHandler,?ex);?? ????????}?? ????????catch?(Error?err)?{?? ????????????triggerAfterCompletionWithError(processedRequest,?response,?mappedHandler,?err);?? ????????}?? ????????finally?{?? ????????????if?(asyncManager.isConcurrentHandlingStarted())?{?? ????????????????//?Instead?of?postHandle?and?afterCompletion?? ????????????????mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest,?response); ????????????????return;?? ????????????}?? ????????????//?Clean?up?any?resources?used?by?a?multipart?request.?? ????????????if?(multipartRequestParsed)?{?? ????????????????cleanupMultipart(processedRequest);?? ????????????}?? ????????}?? ????}??
第一步详细查看：?
Java代码?? protected?HandlerExecutionChain?getHandler(HttpServletRequest?request)?throws?Exception?{? ????????for?(HandlerMapping?hm?:?this.handlerMappings)?{?? ????????????if?(logger.isTraceEnabled())?{?? ????????????????logger.trace(?? ????????????????????????"Testing?handler?map?["?+?hm?+?"]?in?DispatcherServlet?with?name?'"?+?getServletName()?+?"'");?? ????????????}?? ????????????HandlerExecutionChain?handler?=?hm.getHandler(request);?? ????????????if?(handler?!=?null)?{?? ????????????????return?handler;?? ????????????}?? ????????}?? ????????return?null;?? ????}??
可以看到就是通过遍历所有已注册的HandlerMapping来找到对应的handler,然后构建出一个HandlerExecutionChain，它包含了handler和HandlerMapping本身的一些拦截器，如下?
Java代码?? public?class?HandlerExecutionChain?{?? ?? ????private?final?Object?handler;?? ?? ????private?HandlerInterceptor[]?interceptors;?? ?? ????private?List<HandlerInterceptor>?interceptorList;?? ?????????? ????????//其他代码省略?? }??
其中HandlerMapping的getHandler实现：?
Java代码?? public?final?HandlerExecutionChain?getHandler(HttpServletRequest?request)?throws?Exception?{?? ????????Object?handler?=?getHandlerInternal(request);?? ????????if?(handler?==?null)?{?? ????????????handler?=?getDefaultHandler();?? ????????}?? ????????if?(handler?==?null)?{?? ????????????return?null;?? ????????}?? ????????//?Bean?name?or?resolved?handler??? ????????if?(handler?instanceof?String)?{?? ????????????String?handlerName?=?(String)?handler;?? ????????????handler?=?getApplicationContext().getBean(handlerName);?? ????????}?? ????????return?getHandlerExecutionChain(handler,?request);?? ????}??
这里的getHandlerInternal(request)是个抽象方法，由具体的HandlerMapping来实现，获取到的handler如果为空,则获取默认配置的handler，如果handler为String类型，则表示这个则会去Spring容器里面去找这样名字的bean。?
再看下BeanNameUrlHandlerMapping的getHandlerInternal（request）的具体实现（通过一系列的接口设计，之后再好好看看这个设计，到BeanNameUrlHandlerMapping这只用实现该方法中的一部分），如下?
Java代码?? public?class?BeanNameUrlHandlerMapping?extends?AbstractDetectingUrlHandlerMapping?{?? ?? ????/**? ?????*?Checks?name?and?aliases?of?the?given?bean?for?URLs,?starting?with?"/".? ?????*/?? [email protected] ????protected?String[]?determineUrlsForHandler(String?beanName)?{?? ????????List<String>?urls?=?new?ArrayList<String>();?? ????????if?(beanName.startsWith("/"))?{?? ????????????urls.add(beanName);?? ????????}?? ????????String[]?aliases?=?getApplicationContext().getAliases(beanName);?? ????????for?(String?alias?:?aliases)?{?? ????????????if?(alias.startsWith("/"))?{?? ????????????????urls.add(alias);?? ????????????}?? ????????}?? ????????return?StringUtils.toStringArray(urls);?? ????}?? ?? }??
这里面注释说，bean的name必须以/开头，它才处理，将信息存储在Map<String, Object> handlerMap中，对于本工程来说就是{'/index':HomeAction对象}。?
至此这里完成了第一步，下面开始第二步，即方法HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());的具体实现：?
Java代码?? protected?HandlerAdapter?getHandlerAdapter(Object?handler)?throws?ServletException?{?? ????????for?(HandlerAdapter?ha?:?this.handlerAdapters)?{?? ????????????if?(logger.isTraceEnabled())?{?? ????????????????logger.trace("Testing?handler?adapter?["?+?ha?+?"]");?? ????????????}?? ????????????if?(ha.supports(handler))?{?? ????????????????return?ha;?? ????????????}?? ????????}?? ????????throw?new?ServletException("No?adapter?for?handler?["?+?handler?+?? ????????????????"]:?The?DispatcherServlet?configuration?needs?to?include?a?HandlerAdapter?that?supports?this?handler");?? ????}??
遍历所有的HandlerAdapter,判断他们是否支持这个handler。?
我们来看下HttpRequestHandlerAdapter的supports(handler)方法：?
Java代码?? public?class?HttpRequestHandlerAdapter?implements?HandlerAdapter?{?? ?? [email protected] ????public?boolean?supports(Object?handler)?{?? ??????????//就是判断handler是否实现了HttpRequestHandler接口?? ????????return?(handler?instanceof?HttpRequestHandler);?? ????}?? ?? [email protected] ????public?ModelAndView?handle(HttpServletRequest?request,?HttpServletResponse?response,?Object?handler)?? ????????????throws?Exception?{?? ???????????//若handler实现了HttpRequestHandler接口，则调用该接口的方法，执行我们在该方法中写的业务逻辑?? ????????((HttpRequestHandler)?handler).handleRequest(request,?response);?? ????????return?null;?? ????}?? ?? [email protected] ????public?long?getLastModified(HttpServletRequest?request,?Object?handler)?{?? ????????if?(handler?instanceof?LastModified)?{?? ????????????return?((LastModified)?handler).getLastModified(request);?? ????????}?? ????????return?-1L;?? ????}?? ?? }??
同理SimpleControllerHandlerAdapter也是这样类似的逻辑?
Java代码?? public?class?SimpleControllerHandlerAdapter?implements?HandlerAdapter?{?? ?? [email protected] ????public?boolean?supports(Object?handler)?{?? ????????return?(handler?instanceof?Controller);?? ????}?? ?? [email protected] ????public?ModelAndView?handle(HttpServletRequest?request,?HttpServletResponse?response,?Object?handler)?? ????????????throws?Exception?{?? ?? ????????return?((Controller)?handler).handleRequest(request,?response);?? ????}?? ?? [email protected] ????public?long?getLastModified(HttpServletRequest?request,?Object?handler)?{?? ????????if?(handler?instanceof?LastModified)?{?? ????????????return?((LastModified)?handler).getLastModified(request);?? ????????}?? ????????return?-1L;?? ????}?? ?? }??
剩余两个AnnotationMethodHandlerAdapter和RequestMappingHandlerAdapter就比较复杂，我也没看。?
按照本工程的配置，则SimpleControllerHandlerAdapter是支持HomeAction的，然后就会执行SimpleControllerHandlerAdapter的handle(processedRequest, response, mappedHandler.getHandler())方法。本质上就会调用HomeAction实现Controller接口的方法。至此就分析完了。?
了解过程了之后，然后就是最重要的也是经常配置出问题的地方。DispatcherServlet的handlerMappings和handlerAdapters的来源问题。?
DispatcherServlet初始化的时候，会调用一个方法如下：?
Java代码?? protected?void?initStrategies(ApplicationContext?context)?{?? ????????initMultipartResolver(context);?? ????????initLocaleResolver(context);?? ????????initThemeResolver(context);?? //初始化一些HandlerMapping?? ????????initHandlerMappings(context);?? //初始化一些HandlerAdapter?? ????????initHandlerAdapters(context);?? ????????initHandlerExceptionResolvers(context);?? ????????initRequestToViewNameTranslator(context);?? ????????initViewResolvers(context);?? ????????initFlashMapManager(context);?? ????}??
这里可以看到，它会初始化一些HandlerMapping和HandlerAdapter，这两个方法非常重要，理解了这两个方法你就会知道，配置不对问题出在哪里，下面具体看下这两个方法：?
Java代码?? private?void?initHandlerMappings(ApplicationContext?context)?{?? ????????this.handlerMappings?=?null;?? ?? ????????if?(this.detectAllHandlerMappings)?{?? ????????????//?Find?all?HandlerMappings?in?the?ApplicationContext,?including?ancestor?contexts.?? ????????????Map<String,?HandlerMapping>?matchingBeans?=?? ????????????????????BeanFactoryUtils.beansOfTypeIncludingAncestors(context,?HandlerMapping.class,?true,?false);?? ????????????if?(!matchingBeans.isEmpty())?{?? ????????????????this.handlerMappings?=?new?ArrayList<HandlerMapping>(matchingBeans.values());?? ????????????????//?We?keep?HandlerMappings?in?sorted?order.?? ????????????????OrderComparator.sort(this.handlerMappings);?? ????????????}?? ????????}?? ????????else?{?? ????????????try?{?? ????????????????HandlerMapping?hm?=?context.getBean(HANDLER_MAPPING_BEAN_NAME,?HandlerMapping.class);?? ????????????????this.handlerMappings?=?Collections.singletonList(hm);?? ????????????}?? ????????????catch?(NoSuchBeanDefinitionException?ex)?{?? ????????????????//?Ignore,?we'll?add?a?default?HandlerMapping?later.?? ????????????}?? ????????}?? ?? ????????//?Ensure?we?have?at?least?one?HandlerMapping,?by?registering?? ????????//?a?default?HandlerMapping?if?no?other?mappings?are?found.?? ????????if?(this.handlerMappings?==?null)?{?? ????????????this.handlerMappings?=?getDefaultStrategies(context,?HandlerMapping.class);?? ????????????if?(logger.isDebugEnabled())?{?? ????????????????logger.debug("No?HandlerMappings?found?in?servlet?'"?+?getServletName()?+?"':?using?default");?? ????????????}?? ????????}?? ????}??
detectAllHandlerMappings是DispatcherServlet的一个属性，你是可以在web.xml中配置的，默认是true，如果为true,则会去从本工程mvc-servlet.xml文件中去探测所有实现了HandlerMapping的bean，如果有，则加入DispatcherServlet的handlerMappings中。如果detectAllHandlerMappings为false,则直接去容器中找id="handlerMapping"且实现了HandlerMapping的bean.如果以上都没找到，则会去加载默认的HandlerMapping。?
Java代码?? /**?Detect?all?HandlerMappings?or?just?expect?"handlerMapping"?bean??*/?? ????private?boolean?detectAllHandlerMappings?=?true;??
本工程由于没有配置HandlerMapping,所以它会去加载默认的，下面看看默认的配置是什么?
Java代码?? protected?<T>?List<T>?getDefaultStrategies(ApplicationContext?context,?Class<T>?strategyInterface)?{?? ????????String?key?=?strategyInterface.getName();?? //defaultStrategies存储了默认的配置?? ????????String?value?=?defaultStrategies.getProperty(key);?? ????????if?(value?!=?null)?{?? ????????????String[]?classNames?=?StringUtils.commaDelimitedListToStringArray(value);?? ????????????List<T>?strategies?=?new?ArrayList<T>(classNames.length);?? ????????????for?(String?className?:?classNames)?{?? ????????????????try?{?? ????????????????????Class<?>?clazz?=?ClassUtils.forName(className,?DispatcherServlet.class.getClassLoader());?? ????????????????????Object?strategy?=?createDefaultStrategy(context,?clazz);?? ????????????????????strategies.add((T)?strategy);?? ????????????????}?? ????????????????catch?(ClassNotFoundException?ex)?{?? ????????????????????throw?new?BeanInitializationException(?? ????????????????????????????"Could?not?find?DispatcherServlet's?default?strategy?class?["?+?className?+?? ????????????????????????????????????"]?for?interface?["?+?key?+?"]",?ex);?? ????????????????}?? ????????????????catch?(LinkageError?err)?{?? ????????????????????throw?new?BeanInitializationException(?? ????????????????????????????"Error?loading?DispatcherServlet's?default?strategy?class?["?+?className?+?? ????????????????????????????????????"]?for?interface?["?+?key?+?"]:?problem?with?class?file?or?dependent?class",?err);?? ????????????????}?? ????????????}?? ????????????return?strategies;?? ????????}?? ????????else?{?? ????????????return?new?LinkedList<T>();?? ????????}?? ????}??
继续看看defaultStrategies是如何初始化的：?
Java代码?? private?static?final?Properties?defaultStrategies;?? ?? ????static?{?? ????????//?Load?default?strategy?implementations?from?properties?file.?? ????????//?This?is?currently?strictly?internal?and?not?meant?to?be?customized?? ????????//?by?application?developers.?? ????????try?{?? //这里的DEFAULT_STRATEGIES_PATH就是DispatcherServlet.properties?? ????????????ClassPathResource?resource?=?new?ClassPathResource(DEFAULT_STRATEGIES_PATH,?DispatcherServlet.class);?? ????????????defaultStrategies?=?PropertiesLoaderUtils.loadProperties(resource);?? ????????}?? ????????catch?(IOException?ex)?{?? ????????????throw?new?IllegalStateException("Could?not?load?'DispatcherServlet.properties':?"?+?ex.getMessage());?? ????????}?? ????}??
这里使用静态代码块来加载配置文件DispatcherServlet.properties，它所在位置就是和DispatcherServlet同一目录下面的，如下图所示：?
该默认的配置文件的内容如下：?
Java代码?? #?Default?implementation?classes?for?DispatcherServlet's?strategy?interfaces.?? #?Used?as?fallback?when?no?matching?beans?are?found?in?the?DispatcherServlet?context.?? #?Not?meant?to?be?customized?by?application?developers.?? ?? org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver?? ?? org.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolver?? ?? #这里就是默认的HandlerMapping的配置?? org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\?? ????org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping?? #这里就是默认的HandlerAdapter的配置?? org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\?? ????org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\?? ????org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter?? ?? org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerExceptionResolver,\?? ????org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\?? ????org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver?? ?? org.springframework.web.servlet.RequestToViewNameTranslator=org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator?? ?? org.springframework.web.servlet.ViewResolver=org.springframework.web.servlet.view.InternalResourceViewResolver?? ?? org.springframework.web.servlet.FlashMapManager=org.springframework.web.servlet.support.SessionFlashMapManager??
也就是说，当你什么都没有配置时，默认会加载以上的配置。正是由于有了上述默认配置的BeanNameUrlHandlerMapping（它要求name必须是以/开头的），它才会存储我们在mvc-servlet.xml中配置的<bean name="/index" class="com.lg.mvc.HomeAction"></bean>,同样正是由于有了SimpleControllerHandlerAdapter（由于handler实现了Controller接口，所以它的support方法支持我们的handler），才会调度执行HomeAction的handleRequest方法 |
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