太厉害了！这是我见过最好的 SpringMVC 源码分析

//org.springframework.web.servlet.DispatcherServletprotected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {		HttpServletRequest processedRequest = request;		//执行器链，包含了handler和一些拦截器		HandlerExecutionChain mappedHandler = null;		boolean multipartRequestParsed = false;		//异步管理器		WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
		try {			ModelAndView mv = null;			Exception dispatchException = null;
			try {				//1. 检查是否是文件上传的请求				processedRequest = checkMultipart(request);				multipartRequestParsed = (processedRequest != request);
				// Determine handler for the current request.				/*					2. 取得处理当前请求的Controller，这里也称为Handler，即处理器。这里并不是直接返回controller，					而是返回HandlerExecutionChain  请求处理链对象 该对象封装了Handler和Inteceptor				 */				mappedHandler = getHandler(processedRequest);				if (mappedHandler == null) {					// 如果handler为空， 则返回404					noHandlerFound(processedRequest, response);					return;				}
				// Determine handler adapter for the current request.				// 3. 获取处理请求的处理器适配器 HandlerAdapter				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
				// Process last-modified header, if supported by the handler.				// 处理last-modeified 请求头				String method = request.getMethod();				boolean isGet = "GET".equals(method);				if (isGet || "HEAD".equals(method)) {					long lastModified = ha.getLastModified(request, mappedHandler.getHandler());					if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {						return;					}				}				//===============拦截器的第一个拦截时机				if (!mappedHandler.applyPreHandle(processedRequest, response)) {					return;				}
				// Actually invoke the handler.				// 4 实际处理器处理请求，返回结果视图对象				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
				if (asyncManager.isConcurrentHandlingStarted()) {					return;				}				//结果视图对象的处理				applyDefaultViewName(processedRequest, mv);
				//==============拦截器的第二个拦截时机				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);			}			//跳转视图页面，渲染视图			processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);		}		catch (Exception ex) {			//最终会调用HandlerInterceptor的afterCompletion方法			//========拦截器的第三个拦截时机————视图页面渲染完成之后拦截			triggerAfterCompletion(processedRequest, response, mappedHandler, ex);		}		catch (Throwable err) {			//最终会调用HandlerInterceptor的afterCompletion方法			//========拦截器的第三个拦截时机————视图页面渲染完成之后拦截			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);				}			}		}	}

	@Nullable	protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {        //handlerMappings是一个 ArrayList ———— List<HandlerMapping> handlerMappings        //而HandlerMapping 则存储了url和handler的映射关系		if (this.handlerMappings != null) {            /**			 * 遍历 handlerMappings ：			 * 	1. BeanNameUrlHandlerMapping ，早期的一种使用方式			 * 	2. RequestMappingHandlerMapping，我们的请求所使用的			 */			for (HandlerMapping mapping : this.handlerMappings) {				HandlerExecutionChain handler = mapping.getHandler(request);				if (handler != null) {					return handler;				}			}		}		return null;	}

	protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {        //List<HandlerAdapter> handlerAdapters		if (this.handlerAdapters != null) {            /*				遍历 handlerAdapters：				遍历各个HandlerAdapter，看哪个Adapter⽀持处理当前Handler：				handlerAdapters是一个List<HandlerAdapter>，HandlerAdapter是一个接口，里面有几个实现类:				1. HttpRequestHandlerAdapter ——实现接口的方式				2. SimpleControllerHandlerAdapter ——实现Controller接口的方式				3. RequestMappingHandlerAdapter ——是不是HandlerMethod（RequestMappingHandlerMapping封装的）的实例			 */			for (HandlerAdapter adapter : this.handlerAdapters) {				if (adapter.supports(handler)) {					return adapter;				}			}		}		throw new ServletException("No adapter for handler [" + handler +				"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");	}

//org.springframework.web.servlet.DispatcherServlet		//多部件解析器，文件上传之类的@Nullableprivate MultipartResolver multipartResolver;
//区域化 国际化解析器@Nullableprivate LocaleResolver localeResolver;
//主题解析器@Nullableprivate ThemeResolver themeResolver;
//处理器映射器组件@Nullableprivate List<HandlerMapping> handlerMappings;
//处理器适配器组件@Nullableprivate List<HandlerAdapter> handlerAdapters;
//异常解析器@Nullableprivate List<HandlerExceptionResolver> handlerExceptionResolvers;
//默认视图名转换器组件@Nullableprivate RequestToViewNameTranslator viewNameTranslator;
//flash属性管理组件@Nullableprivate FlashMapManager flashMapManager;
//视图解析器@Nullableprivate List<ViewResolver> viewResolvers;

//org.springframework.web.servlet.DispatcherServlet
//主要完成组件的初始化@Overrideprotected void onRefresh(ApplicationContext context) {	//初始化策略	initStrategies(context);}

protected void initStrategies(ApplicationContext context) {   // 多文件上传的组件   initMultipartResolver(context);   // 初始化本地语语言环境   initLocaleResolver(context);   // 初始化模板处理器   initThemeResolver(context);   // 初始化HandlerMapping   initHandlerMappings(context);   // 初始化参数适配器   initHandlerAdapters(context);   // 初始化异常拦截器   initHandlerExceptionResolvers(context);   // 初始化视图预处理器   initRequestToViewNameTranslator(context);   // 初始化视图转换器   initViewResolvers(context);   // 初始化FlashMap 管理器   initFlashMapManager(context);}

//org.springframework.web.servlet.DispatcherServlet#doDispatch
// 4 实际处理器处理请求，返回结果视图对象mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

//跳转视图页面，渲染视图processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);