@Override  protected final void doGet(HttpServletRequest request, HttpServletResponse response)          throws ServletException, IOException {        processRequest(request, response);  }  @Override  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 {      //记录当前时间，用于计算web请求的处理时间      long startTime = System.currentTimeMillis();      Throwable failureCause = null;      //根据当前request创建对应的LocaleContext和RequestAttributes,并绑定到当前线程      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 {          //委托给doService方法进一步处理          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 {          //请求处理结束后回复线程到原始状态          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");                  }              }          }          //请求处理结束后无论成功与否发布事件通知          publishRequestHandledEvent(request, startTime, failureCause);      }  }

@Override  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
     
       attributesSnapshot = null;      if (WebUtils.isIncludeRequest(request)) {          attributesSnapshot = new HashMap
      
       ();          Enumeration
        attrNames = request.getAttributeNames();          while (attrNames.hasMoreElements()) {              String attrName = (String) attrNames.nextElement();              if (this.cleanupAfterInclude || attrName.startsWith("org.springframework.web.servlet")) {                  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);              }          }      }  }
      
     

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类型的request则转换request为MultipartHttpServletRequest类型的request              processedRequest = checkMultipart(request);              multipartRequestParsed = (processedRequest != request);                // Determine handler for the current request.              //根据request信息寻找对应的handler              mappedHandler = getHandler(processedRequest, false);              if (mappedHandler == null || mappedHandler.getHandler() == null) {                  //如果没有找到对应的handler则通过response反馈错误信息                  noHandlerFound(processedRequest, response);                  return;              }                // Determine handler adapter for the current request.              //根据当前的handler寻找对应的handlerAdapter              HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());                // Process last-modified header, if supported by the handler.              String method = request.getMethod();              //如果handler支持last-modified头处理              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;                  }              }              //拦截器的preHandler方法的调用              if (!mappedHandler.applyPreHandle(processedRequest, response)) {                  return;              }              // Actually invoke the handler.              //真正的激活handler并返回视图              mv = ha.handle(processedRequest, response, mappedHandler.getHandler());                if (asyncManager.isConcurrentHandlingStarted()) {                  return;              }              //视图名称转换应用于需要添加前缀后缀的情况              applyDefaultViewName(request, mv);              //调用所有拦截器的postHandle方法              mappedHandler.applyPostHandle(processedRequest, response, mv);          }          catch (Exception ex) {              dispatchException = ex;          }          //页面处理          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              if (mappedHandler != null) {                  mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);              }          }          else {              // Clean up any resources used by a multipart request.              if (multipartRequestParsed) {                  cleanupMultipart(processedRequest);              }          }      }  }  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()) {          //处理页面跳转          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) {          //完成激活处理触发器          mappedHandler.triggerAfterCompletion(request, response, null);      }  }