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 {

                    //对文件上传类型的数据进行处理，使用MultipartResolver解析

                    processedRequest = checkMultipart(request);

                    multipartRequestParsed = (processedRequest != request);

                    //使用HandlerMapping进行映射，将一个Handler和多个HandlerInterceptor封装为HandlerExecutionChain对象

                    mappedHandler = getHandler(processedRequest);

                    if (mappedHandler == null || mappedHandler.getHandler() == null) {

                        noHandlerFound(processedRequest, response);

                        return;

                    }

                    //根据Handler获取合适的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;

                        }

                    }

                    /*

                     * 调用拦截器的preHandle()，返回true继续执行下一个拦截器或处理器，返回false中断流程并执行执行成功的拦截器的afterCompletion()。

    　　　　　　　　　               */

                    if (!mappedHandler.applyPreHandle(processedRequest, response)) {

                        return;

                    }

                    //使用HandlerAdapter执行Handler并返回ModeAndView

                    mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

                    if (asyncManager.isConcurrentHandlingStarted()) {

                        return;

                    }

                    applyDefaultViewName(processedRequest, mv);

                    //调用拦截器的postHandle()方法

                    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);

                }

                //处理转发结果，包含ModeAndView的视图解析，视图解析后调用拦截器的afterCompletion()函数

                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()) {

                    // 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);

                    }

                }

            }

        }