public interface HandlerMapping {
	/**
	 * 返回一個(gè)包含handler Object和所有攔截器的HandlerExecutionChain
	 */
	@Nullable
	HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
}

  //容器中HandlerMapping接口實(shí)現(xiàn)類(lèi)集合	
  @Nullable
	private List<HandlerMapping> handlerMappings;

	private void initHandlerMappings(ApplicationContext context) {
		this.handlerMappings = null;
		//判定是否檢測(cè)所有的HandlerMapping
		if (this.detectAllHandlerMappings) {
			//查看容器中所有的實(shí)現(xiàn)了HandlerMapping的bean
			Map<String, HandlerMapping> matchingBeans =
					BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false);
			if (!matchingBeans.isEmpty()) {
				this.handlerMappings = new ArrayList<>(matchingBeans.values());
				// 使用實(shí)現(xiàn)類(lèi)的order進(jìn)行優(yōu)先級(jí)排序，升序
				AnnotationAwareOrderComparator.sort(this.handlerMappings);
			}
		}
		else {
			try {
        //加載缺省的HandlerMapping
				HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class);
				this.handlerMappings = Collections.singletonList(hm);
			}
			catch (NoSuchBeanDefinitionException ex) {
				// Ignore, we'll add a default HandlerMapping later.
			}
		}

		// Ensure we have at least one HandlerMapping, by registering
		// a default HandlerMapping if no other mappings are found.
		if (this.handlerMappings == null) {
			this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class);
			if (logger.isTraceEnabled()) {
				logger.trace("No HandlerMappings declared for servlet '" + getServletName() +
						"': using default strategies from DispatcherServlet.properties");
			}
		}
	}

	/**
	 * 根據(jù)request請(qǐng)求獲取HandlerExecutionChain處理程序執(zhí)行器鏈
	 * Look up a handler for the given request, falling back to the default
	 * handler if no specific one is found.
	 * @param request current HTTP request
	 * @return the corresponding handler instance, or the default handler
	 * @see #getHandlerInternal
	 */
	@Override
	@Nullable
	public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
    //獲取Handler object即HandlerMethod對(duì)象
		Object handler = getHandlerInternal(request);
		if (handler == null) {
      //如果沒(méi)有找到匹配的HandlerMethod對(duì)象，那么就獲取默認(rèn)的handler
			handler = getDefaultHandler();
		}
		if (handler == null) {
			return null;
		}
		// Bean name or resolved handler?
		if (handler instanceof String) {
			String handlerName = (String) handler;
			handler = obtainApplicationContext().getBean(handlerName);
		}
		//根據(jù)上面獲取的handler object獲取處理程序執(zhí)行器鏈類(lèi)HandlerExecutionChain
		HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);

		if (logger.isTraceEnabled()) {
			logger.trace("Mapped to " + handler);
		}
		else if (logger.isDebugEnabled() && !request.getDispatcherType().equals(DispatcherType.ASYNC)) {
			logger.debug("Mapped to " + executionChain.getHandler());
		}
		//有跨域相關(guān)配置時(shí)執(zhí)行如下代碼
		if (hasCorsConfigurationSource(handler) || CorsUtils.isPreFlightRequest(request)) {
			CorsConfiguration config = (this.corsConfigurationSource != null ? this.corsConfigurationSource.getCorsConfiguration(request) : null);
			CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
			config = (config != null ? config.combine(handlerConfig) : handlerConfig);
			executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
		}

		return executionChain;
	}

	/**
	 * 通過(guò)request請(qǐng)求獲取對(duì)應(yīng)的HandlerMethod類(lèi)
	 */
	@Override
	protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
		//獲取請(qǐng)求URL
    String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
		request.setAttribute(LOOKUP_PATH, lookupPath);
		this.mappingRegistry.acquireReadLock();
		try {
      //獲取URL對(duì)應(yīng)的HandlerMethod,重點(diǎn)是我們?nèi)绾潍@取HandlerMethod對(duì)象？
			HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
			return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
		}
		finally {
			this.mappingRegistry.releaseReadLock();
		}
	}

	/**
	 * 通過(guò)URL獲取HandlerMethod對(duì)象
	 */
	@Nullable
	protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
		List<Match> matches = new ArrayList<>();
    //通過(guò)URL獲取RequestMappingInfo集合
		List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
		if (directPathMatches != null) {
      //將RequestMappingInfo對(duì)象和HandlerMethod對(duì)象封裝到Match對(duì)象中存到matches集合
			addMatchingMappings(directPathMatches, matches, request);
		}
		if (matches.isEmpty()) {
			// No choice but to go through all mappings...
			addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
		}

		if (!matches.isEmpty()) {
      //獲取集合中第一個(gè)Match對(duì)象
			Match bestMatch = matches.get(0);
			if (matches.size() > 1) {
				Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
				matches.sort(comparator);
				bestMatch = matches.get(0);
				if (logger.isTraceEnabled()) {
					logger.trace(matches.size() + " matching mappings: " + matches);
				}
				if (CorsUtils.isPreFlightRequest(request)) {
					return PREFLIGHT_AMBIGUOUS_MATCH;
				}
				Match secondBestMatch = matches.get(1);
				if (comparator.compare(bestMatch, secondBestMatch) == 0) {
					Method m1 = bestMatch.handlerMethod.getMethod();
					Method m2 = secondBestMatch.handlerMethod.getMethod();
					String uri = request.getRequestURI();
					throw new IllegalStateException(
							"Ambiguous handler methods mapped for '" + uri + "': {" + m1 + ", " + m2 + "}");
				}
			}
			request.setAttribute(BEST_MATCHING_HANDLER_ATTRIBUTE, bestMatch.handlerMethod);
			handleMatch(bestMatch.mapping, lookupPath, request);
      //返回HandlerMethod對(duì)象
			return bestMatch.handlerMethod;
		}
		else {
			return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
		}
	}

	 //URL和RequestMappingInfo集合	
	 private final MultiValueMap<String, T> urlLookup = new LinkedMultiValueMap<>();		
		/**
		 * 返回與URL匹配的RequestMappingInfo集合
		 */
		@Nullable
		public List<T> getMappingsByUrl(String urlPath) {
			return this.urlLookup.get(urlPath);
		}

	private void addMatchingMappings(Collection<T> mappings, List<Match> matches, HttpServletRequest request) {
    //循環(huán)遍歷RequestMappingInfo對(duì)象
		for (T mapping : mappings) {
      //
			T match = getMatchingMapping(mapping, request);
			if (match != null) {
        //通過(guò)this.mappingRegistry.getMappings()獲取HandlerMethod對(duì)象
				matches.add(new Match(match, this.mappingRegistry.getMappings().get(mapping)));
			}
		}
	}
	//RequestMappingInfo和HandlerMethod集合
	private final Map<T, HandlerMethod> mappingLookup = new LinkedHashMap<>();
	/**
		 * Return all mappings and handler methods. Not thread-safe.
		 * @see #acquireReadLock()
		 */
		public Map<T, HandlerMethod> getMappings() {
			return this.mappingLookup;
		}

	/**
	 * Return the HandlerExecutionChain for this request.
	 * <p>Tries all handler mappings in order.
	 * @param request current HTTP request
	 * @return the HandlerExecutionChain, or {@code null} if no handler could be found
	 */
	@Nullable
	protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
		if (this.handlerMappings != null) {
      //循環(huán)HandlerMapping實(shí)現(xiàn)類(lèi)集合，其中包括RequestMappingHandlerMapping
			for (HandlerMapping mapping : this.handlerMappings) {
        //調(diào)用HandlerMapping實(shí)現(xiàn)類(lèi)的getHandler方法，并獲取程序執(zhí)行器鏈類(lèi)對(duì)象
				HandlerExecutionChain handler = mapping.getHandler(request);
				if (handler != null) {
          //如果匹配直接返回，否則返回null
					return handler;
				}
			}
		}
		return null;
	}