Spring MVC源码学习笔记

万维钢-《才华与野心》

学问能让你 [配得上] 财富，但是并不一定能带来财富。

但如果一个人搞不清自己到底想要什么，一边说着要求知一边又羡慕人家的成就，自己又没有太大野心去狠心做事，那就是人生观不够自洽。

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 {
				// 检查是否文件上传请求
				processedRequest = checkMultipart(request);
				multipartRequestParsed = (processedRequest != request);

				// 进行映射
				mappedHandler = getHandler(processedRequest);
				if (mappedHandler == null) {
					noHandlerFound(processedRequest, response);
					return;
				}

				// 适配 HandlerMapper, 找到最合适的 HandlerAdapter
				HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

				// Process last-modified header, if supported by the handler.  HTTP缓存相关
				String method = request.getMethod();
				boolean isGet = HttpMethod.GET.matches(method);
				if (isGet || HttpMethod.HEAD.matches(method)) {
					long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
					if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
						return;
					}
				}
				// 触发前置拦截器：preHandle()
				if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					// 返回false就不进行后续处理了
					return;
				}

				// Actually invoke the handler.
				// 调用对应的控制器方法(handleRequest(request, response))，返回一个 ModelAndView 对象
				mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

				if (asyncManager.isConcurrentHandlingStarted()) {
					return;
				}
				// 如果mv有  视图没有，给你设置默认视图
				applyDefaultViewName(processedRequest, mv);
				//触发后置拦截器：postHandle()
				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);
			}
			// 渲染视图，并触发拦截器：afterCompletion()
			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);
				}
			}
		}
	}

protected void initStrategies(ApplicationContext context) {
	// 初始化文件上传解析器
	initMultipartResolver(context);
	initLocaleResolver(context);
	initThemeResolver(context);
	// 初始化 HandlerMapping
	initHandlerMappings(context);
	// 初始化 HandlerAdapter
	initHandlerAdapters(context);
	initHandlerExceptionResolvers(context);
	initRequestToViewNameTranslator(context);
	// 初始化视图解析器
	initViewResolvers(context);
	initFlashMapManager(context);
}

# Default implementation classes for DispatcherServlet's strategy interfaces.
# Used as fallback when no matching beans are found in the DispatcherServlet context.
# Not meant to be customized by application developers.

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.method.annotation.RequestMappingHandlerMapping,\
   org.springframework.web.servlet.function.support.RouterFunctionMapping

org.springframework.web.servlet.HandlerAdapter=org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\
   org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\
   org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter,\
   org.springframework.web.servlet.function.support.HandlerFunctionAdapter


org.springframework.web.servlet.HandlerExceptionResolver=org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver,\
   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

protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
	if (this.handlerMappings != null) {
		for (HandlerMapping mapping : this.handlerMappings) {
			HandlerExecutionChain handler = mapping.getHandler(request);
			// 匹配到一个立即返回，不再继续匹配
			if (handler != null) {
				return handler;
			}
		}
	}
	return null;
}

public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
    // K2: 核心方法，通过请求 URI 来解析到请求对应的 Handler Method
	Object handler = getHandlerInternal(request);
	// 如果没匹配到，则获取默认的 Handler，也就是那个匹配 "/*" 的 Handler
	if (handler == null) {
		handler = getDefaultHandler();
	}
	if (handler == null) {
		return null;
	}
    ...
    // 生成一个控制器执行链
	HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
    ...
	return executionChain;
}

protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
	HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
			(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
	// 筛选出所有跟当前请求匹配的拦截器
	for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
		if (interceptor instanceof MappedInterceptor) {
			MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
			// 如果匹配上了，就把拦截器加入执行链
			if (mappedInterceptor.matches(request)) {
				chain.addInterceptor(mappedInterceptor.getInterceptor());
			}
		}
		else {
			chain.addInterceptor(interceptor);
		}
	}
	return chain;
}

protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
	List<Match> matches = new ArrayList<>();
	List<T> directPathMatches = this.mappingRegistry.getMappingsByDirectPath(lookupPath);
	if (directPathMatches != null) {
		// 如果根据path能直接匹配的RequestMappingInfo 则用该mapping进行匹配其他条件(method、header等）
		addMatchingMappings(directPathMatches, matches, request);
	}
	if (matches.isEmpty()) {
		// 如果无path匹配，用所有的RequestMappingInfo  通过AntPathMatcher匹配
		addMatchingMappings(this.mappingRegistry.getRegistrations().keySet(), matches, request);
	}
	if (!matches.isEmpty()) {
		// 选择第一个为最匹配的
		Match bestMatch = matches.get(0);
		if (matches.size() > 1) {
			//创建MatchComparator的匹配器对象
			Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
			matches.sort(comparator);

			// 排完序后拿到优先级最高的
			bestMatch = matches.get(0);
		}
		//把最匹配的设置到request中
		request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.getHandlerMethod());
		handleMatch(bestMatch.mapping, lookupPath, request);
		//返回最匹配的
		return bestMatch.getHandlerMethod();
	}
	else { // return null
		return handleNoMatch(this.mappingRegistry.getRegistrations().keySet(), lookupPath, request);
	}
}