SpringMVC执行流程源码分析

SpringMVC执行流程源码分析

我们先来看张图片，帮助我们理解整个流程

 

然后我们开始来解析

首先SpringMVC基于Servlet来运行 那么我们首先来看HttpServletBean这个类 他继承HttpServlet,所以这个HttpServletBean为一个Servlet，我们直接看Init方法，因为init方法在Servlet初始化的时候会执行的一个方法

public final void init() throws ServletException {
   if (logger.isDebugEnabled()) {
      logger.debug("Initializing servlet '" + getServletName() + "'");
   }

   // 在Web.xml中读取配置文件.
   PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
   if (!pvs.isEmpty()) {
      try {
          //通过BeanWrapper代理器创建DispatcherServlet
         BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
         ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
         bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
         initBeanWrapper(bw);
        //设置DispatcherServlet属性
         bw.setPropertyValues(pvs, true);
      }
      catch (BeansException ex) {
         if (logger.isErrorEnabled()) {
            logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
         }
         throw ex;
      }
   }

   // 该类为空实现，由他的子类实现也就是FrameworkServlet
   initServletBean();

   if (logger.isDebugEnabled()) {
      logger.debug("Servlet '" + getServletName() + "' configured successfully");
   }
}

那我们来看FrameworkServlet里的实现

protected final void initServletBean() throws ServletException {
   getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
   if (this.logger.isInfoEnabled()) {
      this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
   }
   long startTime = System.currentTimeMillis();

   try {
      this.webApplicationContext = initWebApplicationContext();
      initFrameworkServlet();
   }
   catch (ServletException ex) {
      this.logger.error("Context initialization failed", ex);
      throw ex;
   }
   catch (RuntimeException ex) {
      this.logger.error("Context initialization failed", ex);
      throw ex;
   }

   if (this.logger.isInfoEnabled()) {
      long elapsedTime = System.currentTimeMillis() - startTime;
      this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
            elapsedTime + " ms");
   }
}

this.webApplicationContext = initWebApplicationContext();

可以看到在这里进行webApplicationContext的初始化，initFrameworkServlet()也可也为空方法，此方法将在设置任何bean属性之后调用,已加载WebApplicationContext,默认实现为空，子类可以覆盖此方法来执行它们需要的任何初始化.

我们点进initWebApplicationContext详细来看

protected WebApplicationContext initWebApplicationContext() {
   WebApplicationContext rootContext =
         WebApplicationContextUtils.getWebApplicationContext(getServletContext());
   WebApplicationContext wac = null;

   if (this.webApplicationContext != null) {
      // A context instance was injected at construction time -> use it
      wac = this.webApplicationContext;
      if (wac instanceof ConfigurableWebApplicationContext) {
         ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
         if (!cwac.isActive()) {
            // The context has not yet been refreshed -> provide services such as
            // setting the parent context, setting the application context id, etc
            if (cwac.getParent() == null) {
               // The context instance was injected without an explicit parent -> set
               // the root application context (if any; may be null) as the parent
               cwac.setParent(rootContext);
            }
            configureAndRefreshWebApplicationContext(cwac);
         }
      }
   }
   if (wac == null) {
      // No context instance was injected at construction time -> see if one
      // has been registered in the servlet context. If one exists, it is assumed
      // that the parent context (if any) has already been set and that the
      // user has performed any initialization such as setting the context id
      wac = findWebApplicationContext();
   }
   if (wac == null) {
      // No context instance is defined for this servlet -> create a local one
      wac = createWebApplicationContext(rootContext);
   }

   if (!this.refreshEventReceived) {
      // Either the context is not a ConfigurableApplicationContext with refresh
      // support or the context injected at construction time had already been
      // refreshed -> trigger initial onRefresh manually here.
      onRefresh(wac);
   }

   if (this.publishContext) {
      // Publish the context as a servlet context attribute.
      String attrName = getServletContextAttributeName();
      getServletContext().setAttribute(attrName, wac);
      if (this.logger.isDebugEnabled()) {
         this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
               "' as ServletContext attribute with name [" + attrName + "]");
      }
   }

   return wac;
}

可以看到这里有个 onRefresh(wac);方法 他就是初始化我们SpringMVC的九大组件 他在DispatcherServlet核心类里，等会我们在细说,我们继续看这里有个createWebApplicationContext方法创建实例

 

protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
   Class<?> contextClass = getContextClass();
   if (this.logger.isDebugEnabled()) {
      this.logger.debug("Servlet with name '" + getServletName() +
            "' will try to create custom WebApplicationContext context of class '" +
            contextClass.getName() + "'" + ", using parent context [" + parent + "]");
   }
   if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
      throw new ApplicationContextException(
            "Fatal initialization error in servlet with name '" + getServletName() +
            "': custom WebApplicationContext class [" + contextClass.getName() +
            "] is not of type ConfigurableWebApplicationContext");
   }
   ConfigurableWebApplicationContext wac =
         (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

   wac.setEnvironment(getEnvironment());
   wac.setParent(parent);
   wac.setConfigLocation(getContextConfigLocation());
   //刷新并配置web应用上下文
   configureAndRefreshWebApplicationContext(wac);

   return wac;

ConfigurableWebApplicationContext wac = (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

可以看到通过反射实例化Web上下文，我们继续来看configureAndRefreshWebApplicationContext(wac);

protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
   if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
      // The application context id is still set to its original default value
      // -> assign a more useful id based on available information
      if (this.contextId != null) {
         wac.setId(this.contextId);
      }
      else {
         // Generate default id...
         wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
               ObjectUtils.getDisplayString(getServletContext().getContextPath()) + '/' + getServletName());
      }
   }

   wac.setServletContext(getServletContext());
   wac.setServletConfig(getServletConfig());
   wac.setNamespace(getNamespace());
   wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));

   // The wac environment's #initPropertySources will be called in any case when the context
   // is refreshed; do it eagerly here to ensure servlet property sources are in place for
   // use in any post-processing or initialization that occurs below prior to #refresh
   ConfigurableEnvironment env = wac.getEnvironment();
   if (env instanceof ConfigurableWebEnvironment) {
      ((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
   }

   postProcessWebApplicationContext(wac);
   applyInitializers(wac);
   wac.refresh();
}

我们注意最后一个调用方法 wac.refresh(); 在这里面可以看到IOC的初始化流程 。我们现在继续回到刚刚说的onRefresh他没有实现 而让他的子类DispatchServlet实现

//DispatchServlet
protected void onRefresh(ApplicationContext context) {
   initStrategies(context);
}

protected void initStrategies(ApplicationContext context) {
    // 初始化文件上传处理
   initMultipartResolver(context);
   //初始化本地化处理
   initLocaleResolver(context);
   //初始化主题处理
   initThemeResolver(context);
  // 初始化处理器映射器(用来保存controller中配置的RequestMapping与Method对应关系)
   initHandlerMappings(context);
   // 初始化处理器适配器(用来动态匹配Method参数 包括类转换 动态赋值)
   initHandlerAdapters(context);
  // 初始化处理器异常处理
   initHandlerExceptionResolvers(context);
  // 初始化请求至视图名转换
   initRequestToViewNameTranslator(context);
  // 初始化视图解析器
   initViewResolvers(context);
  // 初始化flash映射管理器
   initFlashMapManager(context);
}

我们再来看DispatcherServlet的配置文件DispatcherServlet.properties

org.springframework.web.servlet.LocaleResolver=org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver

org.springframework.web.servlet.ThemeResolver=org.springframework.web.servlet.theme.FixedThemeResolver

org.springframework.web.servlet.HandlerMapping=org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,
   org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping

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

这个是DispatcherServlet策略接口的默认实现类。

那我们再捋一次执行过程，我们回到FrameworkServlet 比如用户在前台发送一个请求POST或GET，会调用 FrameworkServlet的doPost/doGet方法，这里以 post请求为例

protected final void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

   processRequest(request, response);
}

protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

   long startTime = System.currentTimeMillis();
   Throwable failureCause = null;

   LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();
   LocaleContext localeContext = buildLocaleContext(request);

   RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();
   ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes);

   WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
   asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor());

   initContextHolders(request, localeContext, requestAttributes);

   try {
     //执行请求
      doService(request, response);
   }
   catch (ServletException ex) {
      failureCause = ex;
      throw ex;
   }
   catch (IOException ex) {
      failureCause = ex;
      throw ex;
   }
   catch (Throwable ex) {
      failureCause = ex;
      throw new NestedServletException("Request processing failed", ex);
   }

   finally {
      resetContextHolders(request, previousLocaleContext, previousAttributes);
      if (requestAttributes != null) {
         requestAttributes.requestCompleted();
      }

      if (logger.isDebugEnabled()) {
         if (failureCause != null) {
            this.logger.debug("Could not complete request", failureCause);
         }
         else {
            if (asyncManager.isConcurrentHandlingStarted()) {
               logger.debug("Leaving response open for concurrent processing");
            }
            else {
               this.logger.debug("Successfully completed request");
            }
         }
      }

      publishRequestHandledEvent(request, response, startTime, failureCause);
   }
}

我们点进doService(request, response);这时又到我们的DispatcherServlet类

protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
   if (logger.isDebugEnabled()) {
      String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : "";
      logger.debug("DispatcherServlet with name '" + getServletName() + "'" + resumed +
            " processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]");
   }

   // Keep a snapshot of the request attributes in case of an include,
   // to be able to restore the original attributes after the include.
   Map<String, Object> attributesSnapshot = null;
   if (WebUtils.isIncludeRequest(request)) {
      attributesSnapshot = new HashMap<String, Object>();
      Enumeration<?> attrNames = request.getAttributeNames();
      while (attrNames.hasMoreElements()) {
         String attrName = (String) attrNames.nextElement();
         if (this.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) {
            attributesSnapshot.put(attrName, request.getAttribute(attrName));
         }
      }
   }

   // Make framework objects available to handlers and view objects.
   request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());
   request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);
   request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);
   request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource());

   FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response);
   if (inputFlashMap != null) {
      request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap));
   }
   request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());
   request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);

   try {
      doDispatch(request, response);
   }
   finally {
      if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
         // Restore the original attribute snapshot, in case of an include.
         if (attributesSnapshot != null) {
            restoreAttributesAfterInclude(request, attributesSnapshot);
         }
      }
   }
}

我们点进 doDispatch(request, response);

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 {
         // 如果是MultipartContent类型则转换为MultiHttpServletRequest类型的request
         processedRequest = checkMultipart(request);
         multipartRequestParsed = (processedRequest != request);

         // 确定当前请求的处理程序,根据request寻找对应的handler
         mappedHandler = getHandler(processedRequest);
         if (mappedHandler == null || mappedHandler.getHandler() == null) {
            noHandlerFound(processedRequest, response);
            return;
         }

         //  // 根据处理器获取handler适配器
         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;
            }
         }
         // 拦截器postHandle方法处理
         if (!mappedHandler.applyPreHandle(processedRequest, response)) {
            return;
         }

         // Actually invoke the handler.
         mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

         if (asyncManager.isConcurrentHandlingStarted()) {
            return;
         }
         // 结果视图对象的处理
         applyDefaultViewName(processedRequest, mv);
        // 拦截器postHandle方法处理
         mappedHandler.applyPostHandle(processedRequest, response, mv);
      }
      catch (Exception ex) {
         dispatchException = ex;
      }
      catch (Throwable err) {
         // As of 4.3, we're processing Errors thrown from handler methods as well,
         // making them available for @ExceptionHandler methods and other scenarios.
         dispatchException = new NestedServletException("Handler dispatch failed", err);
      }
      // 处理最终结果 渲染视图等
      processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
   }
   catch (Exception ex) {
      triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
   }
   catch (Throwable err) {
      triggerAfterCompletion(processedRequest, response, mappedHandler,
            new NestedServletException("Handler processing failed", err));
   }
   finally {
      if (asyncManager.isConcurrentHandlingStarted()) {
         // 请求成功响应之后的方法
         if (mappedHandler != null) {
            mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
         }
      }
      else {
         // Clean up any resources used by a multipart request.
         if (multipartRequestParsed) {
            cleanupMultipart(processedRequest);
         }
      }
   }
}

我们来看getHandler()方法

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;
}

我们继续看hm.getHandler(request);方法的实现来自于HandlerMapping这个接口由AbstractHandlerMapping来实现

public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
  // 根据request获取handler
   Object handler = getHandlerInternal(request);
  // 没有查找到使用默认handler
   if (handler == null) {
      handler = getDefaultHandler();
   }
   if (handler == null) {
      return null;
   }
   //  如果handler是字符串类型 说明是bean名称 需要获取handler bean对象
   if (handler instanceof String) {
      String handlerName = (String) handler;
      handler = getApplicationContext().getBean(handlerName);
   }
 // 封装handler执行链
   HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
   if (CorsUtils.isCorsRequest(request)) {
      CorsConfiguration globalConfig = this.globalCorsConfigSource.getCorsConfiguration(request);
      CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
      CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
      executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
   }
   return executionChain;
}

我们继续来看getHandlerInternal

//AbstractHandlerMethodMapping
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
  // 获取request中的url 用来匹配handler
   String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
   if (logger.isDebugEnabled()) {
      logger.debug("Looking up handler method for path " + lookupPath);
   }
   this.mappingRegistry.acquireReadLock();
   try {
      // 根据路径寻找handler
      HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
      if (logger.isDebugEnabled()) {
         if (handlerMethod != null) {
            logger.debug("Returning handler method [" + handlerMethod + "]");
         }
         else {
            logger.debug("Did not find handler method for [" + lookupPath + "]");
         }
      }
      return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
   }
   finally {
      this.mappingRegistry.releaseReadLock();
   }
}

protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
  
   List<Match> matches = new ArrayList<Match>();
   // 直接匹配
   List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
  // 存在匹配 则添加到匹配列表中
   if (directPathMatches != null) {
      addMatchingMappings(directPathMatches, matches, request);
   }
   // 没有匹配 遍历所有处理方法查找
   if (matches.isEmpty()) {
      // No choice but to go through all mappings...
      addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
   }
    // 存在匹配
   if (!matches.isEmpty()) {
      Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
      Collections.sort(matches, comparator);
      if (logger.isTraceEnabled()) {
         logger.trace("Found " + matches.size() + " matching mapping(s) for [" +
               lookupPath + "] : " + matches);
      }
      // 排序之后获取第一个
      Match bestMatch = matches.get(0);
      // 有多个匹配 会找出第二个进行比较
      if (matches.size() > 1) {
         if (CorsUtils.isPreFlightRequest(request)) {
            return PREFLIGHT_AMBIGUOUS_MATCH;
         }
         Match secondBestMatch = matches.get(1);
         if (comparator.compare(bestMatch, secondBestMatch) == 0) {
            Method m1 = bestMatch.handlerMethod.getMethod();
            Method m2 = secondBestMatch.handlerMethod.getMethod();
            throw new IllegalStateException("Ambiguous handler methods mapped for HTTP path '" +
                  request.getRequestURL() + "': {" + m1 + ", " + m2 + "}");
         }
      }
      // 设置request参数
      handleMatch(bestMatch.mapping, lookupPath, request);
      // 返回匹配的url处理方法
      return bestMatch.handlerMethod;
   }
   else {
      return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
   }
}

我们回到 getHandlerExecutionChain继续来看

protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
  // // 如果当前handler不是执行链类型 则创建一个新的执行链封装
   HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
         (HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
//   当前url
   String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
   // 遍历拦截器 与当前url匹配的添加至执行链中
   for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
      if (interceptor instanceof MappedInterceptor) {
         MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
         if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
            chain.addInterceptor(mappedInterceptor.getInterceptor());
         }
      }
      else {
         chain.addInterceptor(interceptor);
      }
   }
   return chain;
}

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
      HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception {

   boolean errorView = false;

   if (exception != null) {
      if (exception instanceof ModelAndViewDefiningException) {
         logger.debug("ModelAndViewDefiningException encountered", exception);
         mv = ((ModelAndViewDefiningException) exception).getModelAndView();
      }
      else {
         Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
         mv = processHandlerException(request, response, handler, exception);
         errorView = (mv != null);
      }
   }

   // Did the handler return a view to render?
   if (mv != null && !mv.wasCleared()) {
     //渲染
      render(mv, request, response);
      if (errorView) {
         WebUtils.clearErrorRequestAttributes(request);
      }
   }
   else {
      if (logger.isDebugEnabled()) {
         logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() +
               "': assuming HandlerAdapter completed request handling");
      }
   }

   if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
      // Concurrent handling started during a forward
      return;
   }

   if (mappedHandler != null) {
      mappedHandler.triggerAfterCompletion(request, response, null);
   }
}

点进render来看

protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
   // Determine locale for request and apply it to the response.
   Locale locale = this.localeResolver.resolveLocale(request);
   response.setLocale(locale);

   View view;
   if (mv.isReference()) {
      // 解析视图名获取视图对象
      view = resolveViewName(mv.getViewName(), mv.getModelInternal(), locale, request);
      if (view == null) {
         throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
               "' in servlet with name '" + getServletName() + "'");
      }
   }
   else {
      // No need to lookup: the ModelAndView object contains the actual View object.
      view = mv.getView();
      if (view == null) {
         throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " +
               "View object in servlet with name '" + getServletName() + "'");
      }
   }

   // Delegate to the View object for rendering.
   if (logger.isDebugEnabled()) {
      logger.debug("Rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'");
   }
   try {
      if (mv.getStatus() != null) {
         response.setStatus(mv.getStatus().value());
      }
      view.render(mv.getModelInternal(), request, response);
   }
   catch (Exception ex) {
      if (logger.isDebugEnabled()) {
         logger.debug("Error rendering view [" + view + "] in DispatcherServlet with name '" +
               getServletName() + "'", ex);
      }
      throw ex;
   }
}

那我们总结一个核心问题？请求如何路由到具体的Controller上的方法进行处理? 根据请求路径，与已知的handlerMapping进行匹配，并加入interceptors,dispatcherServlet.getHandler()最终调用AbstracteHandlerMapping.getHandlerExecutionChain(..)中进行url与handlerMapping进行匹配，并加入interceptors;

好的 到这里我们解析结束.