SpringMVC源码解读 - HandlerMapping - RequestMappingHandlerMapping请求分发

AbstractHandlerMethodMapping实现接口getHandlerInternal,定义查找流程

RequestMappingInfoHandlerMapping根据RequestMappingInfo,细化匹配条件,并在匹配不到情况下,顽强的使用RequestCondition一再尝试匹配

虽然 RequestMappingHandlerMapping是受益方,但在这边什么都没做(就是在初始化时,根据@Controller,@RequestMapping注解生成RequestMappingInfo;并根据这两个注解判断是否目标Handler  实现isHandler)

AbstractHandlerMethodMapping实现接口getHandlerInternal

　　1. 使用UrlPathHelper查找request对应的path

　　2. 查找path对应的HandlerMethod

　　　　2.1 从urlMap中直接等值匹配查找匹配条件RequestMappingInfo

　　　　2.2 如果等值查找到匹配条件,将其添加到match条件中

　　　　2.3 如果没有找到匹配条件,使用所有的handlerMethod的RequestMappingInfo进行匹配

　　　　2.4 对匹配到的Match进行排序,取出最高优先级的Match,并核对是否是唯一的最高优先级

　　　　2.5 对匹配到条件,没有匹配到条件的两种情况,分别进行封装

　　3. 封装HandlerMethod,确保bean中存的是实例

// AbstractHandlerMethodMapping

实现接口getHandlerInternal

 package org.springframework.web.servlet.handler
     // AbstractHandlerMethodMapping<T>
     /**
      * Look up a handler method for the given request.
      */
     @Override
     protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
         // 就是request对应的url
         String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
         // 查找到处理器,这边的处理器会封装成HandlerMethod
         HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
         // 确保bean中存的是实例
         return (handlerMethod != null) ? handlerMethod.createWithResolvedBean() : null;
     }

// AbstractHandlerMethodMapping

package org.springframework.web.servlet.handler;
public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMapping implements InitializingBean  {
    /**
     * Look up the best-matching handler method for the current request.
     * If multiple matches are found, the best match is selected.
     * @param lookupPath mapping lookup path within the current servlet mapping
     * @param request the current request
     * @return the best-matching handler method, or {@code null} if no match
     * @see #handleMatch(Object, String, HttpServletRequest)
     * @see #handleNoMatch(Set, String, HttpServletRequest)
     */
    protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
        List<Match> matches = new ArrayList<Match>();
        // 从urlMap中直接等值匹配查找匹配条件RequestMappingInfo
        List<T> directPathMatches = this.urlMap.get(lookupPath);
        if (directPathMatches != null) {
            //
            addMatchingMappings(directPathMatches, matches, request);
        }

        if (matches.isEmpty()) {
            // No choice but to go through all mappings
            // 没有匹配的情况下,遍历handlerMethods的全部匹配条件进行查找
            addMatchingMappings(this.handlerMethods.keySet(), matches, request);
        }

        if (!matches.isEmpty()) {
            Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
            Collections.sort(matches, comparator);

            Match bestMatch = matches.get(0);
            if (matches.size() > 1) {
                Match secondBestMatch = matches.get(1);
                if (comparator.compare(bestMatch, secondBestMatch) == 0) {
                    Method m1 = bestMatch.handlerMethod.getMethod();
                    Method m2 = secondBestMatch.handlerMethod.getMethod();
                    // 不能有相同的最优Match
                    throw new IllegalStateException(
                            "Ambiguous handler methods mapped for HTTP path '" + request.getRequestURL() + "': {" +
                            m1 + ", " + m2 + "}");
                }
            }
            // 就是往request域中缓存url中解析出来的参数,mediaType等,这边RequestMappingHandlerMapping也覆写了一下
            handleMatch(bestMatch.mapping, lookupPath, request);
            return bestMatch.handlerMethod;
        }
        else {
            // RequestMappingHandlerMapping
            return handleNoMatch(handlerMethods.keySet(), lookupPath, request);
        }
    }
}

// AbstractHandlerMethodMapping

查找具体符合条件的RequestCondition

 package org.springframework.web.servlet.handler;
 public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMapping implements InitializingBean {

     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, handlerMethods.get(mapping)));
             }
         }
     }

// AbstractHandlerMethodMapping

     /**
      * Check if a mapping matches the current request and return a (potentially
      * new) mapping with conditions relevant to the current request.
      * @param mapping the mapping to get a match for
      * @param request the current HTTP servlet request
      * @return the match, or {@code null} if the mapping doesn't match
      */
     protected abstract T getMatchingMapping(T mapping, HttpServletRequest request);

我们来看看RequestMappingInfoHandlerMapping中的实现,从RequestMappingInfo中查找符合的RequestCondition

// RequestMappingInfoHandlerMapping

     /**
      * Check if the given RequestMappingInfo matches the current request and
      * return a (potentially new) instance with conditions that match the
      * current request -- for example with a subset of URL patterns.
      * @return an info in case of a match; or {@code null} otherwise.
      */
     @Override
     protected RequestMappingInfo getMatchingMapping(RequestMappingInfo info, HttpServletRequest request) {
         return info.getMatchingCondition(request);
     }

// AbstractHandlerMethodMapping

     /**
      * Invoked when a matching mapping is found.
      * @param mapping the matching mapping
      * @param lookupPath mapping lookup path within the current servlet mapping
      * @param request the current request
      */
     protected void handleMatch(T mapping, String lookupPath, HttpServletRequest request) {
         request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, lookupPath);
     }

RequestMappingInfoHandlerMapping中又对其进行了覆写,具体是干啥用的,等看了HandlerAdaptor再说吧

     /**
      * Expose URI template variables, matrix variables, and producible media types in the request.
      * @see HandlerMapping#URI_TEMPLATE_VARIABLES_ATTRIBUTE
      * @see HandlerMapping#MATRIX_VARIABLES_ATTRIBUTE
      * @see HandlerMapping#PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE
      */
     @Override
     protected void handleMatch(RequestMappingInfo info, String lookupPath, HttpServletRequest request) {
         super.handleMatch(info, lookupPath, request);

         Set<String> patterns = info.getPatternsCondition().getPatterns();
         String bestPattern = patterns.isEmpty() ? lookupPath : patterns.iterator().next();
         request.setAttribute(BEST_MATCHING_PATTERN_ATTRIBUTE, bestPattern);

         Map<String, String> uriVariables = getPathMatcher().extractUriTemplateVariables(bestPattern, lookupPath);
         Map<String, String> decodedUriVariables = getUrlPathHelper().decodePathVariables(request, uriVariables);
         request.setAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, decodedUriVariables);

         if (isMatrixVariableContentAvailable()) {
             request.setAttribute(HandlerMapping.MATRIX_VARIABLES_ATTRIBUTE, extractMatrixVariables(request, uriVariables));
         }

         if (!info.getProducesCondition().getProducibleMediaTypes().isEmpty()) {
             Set<MediaType> mediaTypes = info.getProducesCondition().getProducibleMediaTypes();
             request.setAttribute(PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE, mediaTypes);
         }
     }

     /**
      * Invoked when no matching mapping is not found.
      * @param mappings all registered mappings
      * @param lookupPath mapping lookup path within the current servlet mapping
      * @param request the current request
      * @throws ServletException in case of errors
      */
     protected HandlerMethod handleNoMatch(Set<T> mappings, String lookupPath, HttpServletRequest request)
             throws Exception {

         return null;
     }

RequestMappingInfoHandlerMapping,覆写,不死心,再匹配一次

// RequestMappingInfoHandlerMapping

     /**
      * Iterate all RequestMappingInfos once again, look if any match by URL at
      * least and raise exceptions accordingly.
      * @throws HttpRequestMethodNotSupportedException if there are matches by URL
      * but not by HTTP method
      * @throws HttpMediaTypeNotAcceptableException if there are matches by URL
      * but not by consumable/producible media types
      */
     @Override
     protected HandlerMethod handleNoMatch(Set<RequestMappingInfo> requestMappingInfos,
             String lookupPath, HttpServletRequest request) throws ServletException {

         Set<String> allowedMethods = new LinkedHashSet<String>(4);

         Set<RequestMappingInfo> patternMatches = new HashSet<RequestMappingInfo>();
         Set<RequestMappingInfo> patternAndMethodMatches = new HashSet<RequestMappingInfo>();

         for (RequestMappingInfo info : requestMappingInfos) {
             if (info.getPatternsCondition().getMatchingCondition(request) != null) {
                 patternMatches.add(info);
                 if (info.getMethodsCondition().getMatchingCondition(request) != null) {
                     patternAndMethodMatches.add(info);
                 }
                 else {
                     for (RequestMethod method : info.getMethodsCondition().getMethods()) {
                         allowedMethods.add(method.name());
                     }
                 }
             }
         }

         if (patternMatches.isEmpty()) {
             return null;
         }
         else if (patternAndMethodMatches.isEmpty() && !allowedMethods.isEmpty()) {
             throw new HttpRequestMethodNotSupportedException(request.getMethod(), allowedMethods);
         }

         Set<MediaType> consumableMediaTypes;
         Set<MediaType> producibleMediaTypes;
         Set<String> paramConditions;

         if (patternAndMethodMatches.isEmpty()) {
             consumableMediaTypes = getConsumableMediaTypes(request, patternMatches);
             producibleMediaTypes = getProducibleMediaTypes(request, patternMatches);
             paramConditions = getRequestParams(request, patternMatches);
         }
         else {
             consumableMediaTypes = getConsumableMediaTypes(request, patternAndMethodMatches);
             producibleMediaTypes = getProducibleMediaTypes(request, patternAndMethodMatches);
             paramConditions = getRequestParams(request, patternAndMethodMatches);
         }

         if (!consumableMediaTypes.isEmpty()) {
             MediaType contentType = null;
             if (StringUtils.hasLength(request.getContentType())) {
                 try {
                     contentType = MediaType.parseMediaType(request.getContentType());
                 }
                 catch (IllegalArgumentException ex) {
                     throw new HttpMediaTypeNotSupportedException(ex.getMessage());
                 }
             }
             throw new HttpMediaTypeNotSupportedException(contentType, new ArrayList<MediaType>(consumableMediaTypes));
         }
         else if (!producibleMediaTypes.isEmpty()) {
             throw new HttpMediaTypeNotAcceptableException(new ArrayList<MediaType>(producibleMediaTypes));
         }
         else if (!CollectionUtils.isEmpty(paramConditions)) {
             String[] params = paramConditions.toArray(new String[paramConditions.size()]);
             throw new UnsatisfiedServletRequestParameterException(params, request.getParameterMap());
         }
         else {
             return null;
         }
     }