SpringMvc详解

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 {
　　　　　　　　　　　　　　　　     //检查是否是请求是否是multipart（如文件上传），如果是将通过MultipartResolver解析
				processedRequest = checkMultipart(request);
				multipartRequestParsed = processedRequest != request;

				// 请求到处理器（页面控制器）的映射，通过HandlerMapping进行映射 
				mappedHandler = getHandler(processedRequest);
				if (mappedHandler == null || mappedHandler.getHandler() == null) {
					noHandlerFound(processedRequest, response);
					return;
				}

				// 处理器适配，即将我们的处理器包装成相应的适配器（从而支持多种类型的处理器）
				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()) {
						String requestUri = urlPathHelper.getRequestUri(request);
						logger.debug("Last-Modified value for [" + requestUri + "] is: " + lastModified);
					}
					if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
						return;
					}
				}
　　　　　　　　　　　　　　　　　　　//处理拦截器 preHandle　　　　　　　　
				if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					return;
				}

				try {
					// 由适配器执行处理器（调用处理器相应功能处理方法）
					mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
				}
				finally {
					if (asyncManager.isConcurrentHandlingStarted()) {
						return;
					}
				}

				applyDefaultViewName(request, mv)
　　　　　　　　　　　　　　　　　　　//拦截器 postHandle　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　
				mappedHandler.applyPostHandle(processedRequest, response, mv);
			}
			catch (Exception ex) {
				dispatchException = ex;
			}
　　　　　　　　　　　　　　//拦截器 afterHandle
			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);
			}
		}
	}