public interface HandlerMapping {
 // 通過request獲取HandlerExecutionChain對(duì)象
 HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception;
}

@Override
@Nullable
public final HandlerExecutionChain getHandler(HttpServletRequest request) 
 throws Exception {
 // 通過request獲取具體的處理bean，這里handler可能有兩種類型：HandlerMethod和String。
 // 如果是String類型，那么就在BeanFactory中查找該String類型的bean，需要注意的是，返回的
 // bean如果是需要使用RequestMappingHandlerAdapter處理，那么也必須是HandlerMethod類型的
 Object handler = getHandlerInternal(request);
 if (handler == null) {
  // 如果找不到處理方法，則獲取自定義的默認(rèn)handler
  handler = getDefaultHandler();
 }
 if (handler == null) {
  return null;
 }
 if (handler instanceof String) {
  // 如果獲取的handler是String類型的，則在當(dāng)前BeanFactory中獲取該名稱的bean，
  // 并將其作為handler返回
  String handlerName = (String) handler;
  handler = obtainApplicationContext().getBean(handlerName);
 }

 // 獲取當(dāng)前系統(tǒng)中配置的Interceptor，將其與handler一起封裝為一個(gè)HandlerExecutionChain
 HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
 // 這里CorsUtils.isCorsRequest()方法判斷的是當(dāng)前請(qǐng)求是否為一個(gè)跨域的請(qǐng)求，如果是一個(gè)跨域的請(qǐng)求，
 // 則將跨域相關(guān)的配置也一并封裝到HandlerExecutionChain中
 if (CorsUtils.isCorsRequest(request)) {
  CorsConfiguration globalConfig = 
   this.globalCorsConfigSource.getCorsConfiguration(request);
  CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
  CorsConfiguration config = (globalConfig != null ? 
   globalConfig.combine(handlerConfig) : handlerConfig);
  executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
 }
 return executionChain;
}

@Override
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
 // 獲取當(dāng)前request的URI
 String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
 if (logger.isDebugEnabled()) {
  logger.debug("Looking up handler method for path " + lookupPath);
 }
 // 獲取注冊(cè)的Mapping的讀鎖
 this.mappingRegistry.acquireReadLock();
 try {
  // 通過path和request查找具體的HandlerMethod
  HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
  if (logger.isDebugEnabled()) {
   if (handlerMethod != null) {
    logger.debug("Returning handler method [" + handlerMethod + "]");
   } else {
    logger.debug("Did not find handler method for [" + lookupPath + "]");
   }
  }
  // 如果獲取到的bean是一個(gè)String類型的，則在BeanFactory中查找該bean，
  // 并將其封裝為一個(gè)HandlerMethod對(duì)象
  return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
 } finally {
  // 釋放當(dāng)前注冊(cè)的Mapping的讀鎖
  this.mappingRegistry.releaseReadLock();
 }
}

@Nullable
protected HandlerMethod lookupHandlerMethod(String lookupPath, 
  HttpServletRequest request) throws Exception {
 List<Match> matches = new ArrayList<>();
 // 通過uri直接在注冊(cè)的RequestMapping中獲取對(duì)應(yīng)的RequestMappingInfo列表，需要注意的是，
 // 這里進(jìn)行查找的方式只是通過url進(jìn)行查找，但是具體哪些RequestMappingInfo是匹配的，還需要進(jìn)一步過濾
 List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
 if (directPathMatches != null) {
  // 對(duì)獲取到的RequestMappingInfo進(jìn)行進(jìn)一步過濾，并且將過濾結(jié)果封裝為一個(gè)Match列表
  addMatchingMappings(directPathMatches, matches, request);
 }
 if (matches.isEmpty()) {
  // 如果無法通過uri進(jìn)行直接匹配，則對(duì)所有的注冊(cè)的RequestMapping進(jìn)行匹配，這里無法通過uri
  // 匹配的情況主要有三種：
  // ①在RequestMapping中定義的是PathVariable，如/user/detail/{id}；
  // ②在RequestMapping中定義了問號(hào)表達(dá)式，如/user/?etail；
  // ③在RequestMapping中定義了*或**匹配，如/user/detail/**
  addMatchingMappings(this.mappingRegistry.getMappings().keySet(), 
   matches, request);
 }

 if (!matches.isEmpty()) {
  // 對(duì)匹配的結(jié)果進(jìn)行排序，獲取相似度最高的一個(gè)作為結(jié)果返回，這里對(duì)相似度的判斷時(shí)，
  // 會(huì)判斷前兩個(gè)是否相似度是一樣的，如果是一樣的，則直接拋出異常，如果不相同，
  // 則直接返回最高的一個(gè)
  Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
  matches.sort(comparator);
  if (logger.isTraceEnabled()) {
   logger.trace("Found " + matches.size() 
       + " matching mapping(s) for [" + lookupPath + "] : " + matches);
  }
  // 獲取匹配程度最高的一個(gè)匹配結(jié)果
  Match bestMatch = matches.get(0);
  if (matches.size() > 1) {
   // 如果匹配結(jié)果不止一個(gè)，首先會(huì)判斷是否是跨域請(qǐng)求，如果是，
   // 則返回PREFLIGHT_AMBIGUOUS_MATCH，如果不是，則會(huì)判斷前兩個(gè)匹配程度是否相同，
   // 如果相同則拋出異常
   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();
    throw new IllegalStateException("Ambiguous handler methods mapped for" 
     + " HTTP path '" + request.getRequestURL() + "': {" + m1 
     + ", " + m2 + "}");
   }
  }
  // 這里主要是對(duì)匹配結(jié)果的一個(gè)處理，主要包含對(duì)傳入?yún)?shù)和返回的MediaType的處理
  handleMatch(bestMatch.mapping, lookupPath, request);
  return bestMatch.handlerMethod;
 } else {
  // 如果匹配結(jié)果是空的，則對(duì)所有注冊(cè)的Mapping進(jìn)行遍歷，判斷當(dāng)前request具體是哪種情況導(dǎo)致
  // 的無法匹配：①RequestMethod無法匹配；②Consumes無法匹配；③Produces無法匹配；
  // ④Params無法匹配
  return handleNoMatch(this.mappingRegistry.getMappings().keySet(), 
   lookupPath, request);
 }
}

private void addMatchingMappings(Collection<T> mappings, List<Match> matches, 
  HttpServletRequest request) {
 for (T mapping : mappings) {
  T match = getMatchingMapping(mapping, request);
  if (match != null) {
   matches.add(new Match(match, 
    this.mappingRegistry.getMappings().get(mapping)));
  }
 }
}

@Override
@Nullable
public RequestMappingInfo getMatchingCondition(HttpServletRequest request) {
 // 判斷request請(qǐng)求的類型是否與當(dāng)前RequestMethod匹配
 RequestMethodsRequestCondition methods = 
  this.methodsCondition.getMatchingCondition(request);
 // 判斷request請(qǐng)求的參數(shù)是否與RequestMapping中params參數(shù)配置的一致
 ParamsRequestCondition params = this.paramsCondition.getMatchingCondition(request);
 // 判斷request請(qǐng)求的headers是否與RequestMapping中headers參數(shù)配置的一致
 HeadersRequestCondition headers = this.headersCondition.getMatchingCondition(request);
 // 判斷request的請(qǐng)求體類型是否與RequestMapping中配置的consumes參數(shù)配置的一致
 ConsumesRequestCondition consumes = 
  this.consumesCondition.getMatchingCondition(request);
 // 判斷當(dāng)前RequestMapping將要返回的請(qǐng)求體類型是否與request中Accept的header指定的一致
 ProducesRequestCondition produces = 
  this.producesCondition.getMatchingCondition(request);

 // 對(duì)于上述幾個(gè)判斷，如果匹配上了，那么其返回值都不會(huì)為空，因而這里會(huì)對(duì)每個(gè)返回值都進(jìn)行判斷，
 // 如果有任意一個(gè)為空，則說明沒匹配上，那么就返回null
 if (methods == null || params == null || headers == null 
  || consumes == null || produces == null) {
  return null;
 }

 // 對(duì)于前面的匹配，都是一些靜態(tài)屬性的匹配，其中最重要的uri的匹配，主要是正則匹配，
 // 就是在下面這個(gè)方法中進(jìn)行的
 PatternsRequestCondition patterns = 
  this.patternsCondition.getMatchingCondition(request);
 // 如果URI沒匹配上，則返回null
 if (patterns == null) {
  return null;
 }

 // 這里主要是對(duì)用戶自定義的匹配條件進(jìn)行匹配
 RequestConditionHolder custom = 
  this.customConditionHolder.getMatchingCondition(request);
 if (custom == null) {
  return null;
 }

 // 如果上述所有條件都匹配上了，那么就將匹配結(jié)果封裝為一個(gè)RequestMappingInfo返回
 return new RequestMappingInfo(this.name, patterns, methods, params, headers, 
  consumes, produces, custom.getCondition());
}

protected HandlerExecutionChain getHandlerExecutionChain(Object handler, 
  HttpServletRequest request) {
 // 將當(dāng)前handler封裝到HandlerExecutionChain對(duì)象中
 HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
  (HandlerExecutionChain) handler : new HandlerExecutionChain(handler));

 // 獲取當(dāng)前request的URI，用于MappedInterceptor的匹配
 String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
 // 對(duì)當(dāng)前所有注冊(cè)的Interceptor進(jìn)行遍歷，如果其是MappedInterceptor類型，則調(diào)用其matches()
 // 方法，判斷當(dāng)前Interceptor是否能夠應(yīng)用于該request，如果可以，則添加到HandlerExecutionChain中
 for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
  if (interceptor instanceof MappedInterceptor) {
   MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
   if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
    chain.addInterceptor(mappedInterceptor.getInterceptor());
   }
  } else {
   // 如果當(dāng)前Interceptor不是MappedInterceptor類型，則直接將其添加到
   // HandlerExecutionChain中
   chain.addInterceptor(interceptor);
  }
 }
 return chain;
}