AbstractHandlerMapping实现HandlerMapping接口定的getHandler

　　1. 提供getHandlerInternal模板方法给子类实现

　　2. 如果没有获取Handler,则使用默认的defaultHandler

　　3. 如果handler是string类型,从context获取实例

　　4. 通过getHandlerExecutionChain封装handler,添加interceptor

// AbstractHandlerMapping

1     /** 2      * Look up a handler for the given request, falling back to the default 3      * handler if no specific one is found. 4      * @param request current HTTP request 5      * @return the corresponding handler instance, or the default handler 6      * @see #getHandlerInternal 7      */ 8     public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { 9         Object handler = getHandlerInternal(request);10         if (handler == null) {11             handler = getDefaultHandler();12         }13         if (handler == null) {14             return null;15         }16         // Bean name or resolved handler?17         if (handler instanceof String) {18             String handlerName = (String) handler;19             handler = getApplicationContext().getBean(handlerName);20         }21         return getHandlerExecutionChain(handler, request);22     }

// AbstractHandlerMapping

1     /** 2      * Build a HandlerExecutionChain for the given handler, including applicable interceptors. 3      * 
The default implementation simply builds a standard HandlerExecutionChain with 4      * the given handler, the handler mapping's common interceptors, and any {
    @link MappedInterceptor}s 5      * matching to the current request URL. Subclasses may 6      * override this in order to extend/rearrange the list of interceptors. 7      * 
NOTE: The passed-in handler object may be a raw handler or a pre-built 8      * HandlerExecutionChain. This method should handle those two cases explicitly, 9      * either building a new HandlerExecutionChain or extending the existing chain.10      * 
For simply adding an interceptor, consider calling {
    @code super.getHandlerExecutionChain}11      * and invoking {
    @link HandlerExecutionChain#addInterceptor} on the returned chain object.12      * @param handler the resolved handler instance (never {
    @code null})13      * @param request current HTTP request14      * @return the HandlerExecutionChain (never {
    @code null})15      * @see #getAdaptedInterceptors()16      */17     protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {18         HandlerExecutionChain chain =19             (handler instanceof HandlerExecutionChain) ?20                 (HandlerExecutionChain) handler : new HandlerExecutionChain(handler);21 22         chain.addInterceptors(getAdaptedInterceptors());23 24         String lookupPath = urlPathHelper.getLookupPathForRequest(request);25         for (MappedInterceptor mappedInterceptor : mappedInterceptors) {26             if (mappedInterceptor.matches(lookupPath, pathMatcher)) {27                 chain.addInterceptor(mappedInterceptor.getInterceptor());28             }29         }30 31         return chain;32     }

 

接下来看看AbstractUrlHandlerMapping实现的getHandlerInternal

// AbstractUrlHandlerMapping

1     /** 2      * Look up a handler for the URL path of the given request. 3      * @param request current HTTP request 4      * @return the handler instance, or {
    @code null} if none found 5      */ 6     @Override 7     protected Object getHandlerInternal(HttpServletRequest request) throws Exception { 8         // 根据request获取url 9         String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);10         // 根据url查找handler11         Object handler = lookupHandler(lookupPath, request);12         if (handler == null) {13             // 如果没有匹配到handler需要查找默认的,下面需要将PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE缓存到request14             // We need to care for the default handler directly, since we need to15             // expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.16             Object rawHandler = null;17             if ("/".equals(lookupPath)) {18                 rawHandler = getRootHandler();19             }20             if (rawHandler == null) {21                 rawHandler = getDefaultHandler();22             }23             if (rawHandler != null) {24                 // Bean name or resolved handler?25                 if (rawHandler instanceof String) {26                     String handlerName = (String) rawHandler;27                     rawHandler = getApplicationContext().getBean(handlerName);28                 }29                 // 预留的校验handler模板方法,没有使用30                 validateHandler(rawHandler, request);31                 // 添加expose属性到request的拦截器32                 handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);33             }34         }35         if (handler != null && logger.isDebugEnabled()) {36             logger.debug("Mapping [" + lookupPath + "] to " + handler);37         }38         else if (handler == null && logger.isTraceEnabled()) {39             logger.trace("No handler mapping found for [" + lookupPath + "]");40         }41         return handler;42     }

 

// AbstractUrlHandlerMapping

1     /** 2      * Look up a handler instance for the given URL path. 3      * 
Supports direct matches, e.g. a registered "/test" matches "/test", 4      * and various Ant-style pattern matches, e.g. a registered "/t*" matches 5      * both "/test" and "/team". For details, see the AntPathMatcher class. 6      * 
Looks for the most exact pattern, where most exact is defined as 7      * the longest path pattern. 8      * @param urlPath URL the bean is mapped to 9      * @param request current HTTP request (to expose the path within the mapping to)10      * @return the associated handler instance, or {
    @code null} if not found11      * @see #exposePathWithinMapping12      * @see org.springframework.util.AntPathMatcher13      */14     protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {15         // Direct match? 直接根据url进行查找handler16         Object handler = this.handlerMap.get(urlPath);17         if (handler != null) {18             // Bean name or resolved handler?19             if (handler instanceof String) {20                 String handlerName = (String) handler;21                 handler = getApplicationContext().getBean(handlerName);22             }23             validateHandler(handler, request);24             return buildPathExposingHandler(handler, urlPath, urlPath, null);25         }26         // Pattern match? 通过表达式进行匹配具体通过AntPathMatcher实现,具体后面分析27         List
      
        matchingPatterns = new ArrayList
       
        ();28         for (String registeredPattern : this.handlerMap.keySet()) {29             if (getPathMatcher().match(registeredPattern, urlPath)) {30                 matchingPatterns.add(registeredPattern);31             }32         }33         String bestPatternMatch = null;34         Comparator
        
          patternComparator = getPathMatcher().getPatternComparator(urlPath);35         if (!matchingPatterns.isEmpty()) {36             Collections.sort(matchingPatterns, patternComparator);37             if (logger.isDebugEnabled()) {38                 logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);39             }40             // order序号最小的优先级最高41             bestPatternMatch = matchingPatterns.get(0);42         }43         if (bestPatternMatch != null) {44             handler = this.handlerMap.get(bestPatternMatch);45             // Bean name or resolved handler?46             if (handler instanceof String) {47                 String handlerName = (String) handler;48                 handler = getApplicationContext().getBean(handlerName);49             }50             validateHandler(handler, request);51             String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestPatternMatch, urlPath);52 53             // There might be multiple 'best patterns', let's make sure we have the correct URI template variables54             // for all of them55             Map
         
           uriTemplateVariables = new LinkedHashMap
          
           ();56 for (String matchingPattern : matchingPatterns) {57 if (patternComparator.compare(bestPatternMatch, matchingPattern) == 0) {58 Map
           
             vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath);59 Map
            
              decodedVars = getUrlPathHelper().decodePathVariables(request, vars);60 uriTemplateVariables.putAll(decodedVars);61 }62 }63 if (logger.isDebugEnabled()) {64 logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables);65 }66 return buildPathExposingHandler(handler, bestPatternMatch, pathWithinMapping, uriTemplateVariables);67 }68 // No handler found...69 return null;70 }
            
           
          
         
        
       
      

 

 

设计用于校验Handler,实际什么都没做,包括子类.

1     /** 2      * Validate the given handler against the current request. 3      * 
The default implementation is empty. Can be overridden in subclasses, 4      * for example to enforce specific preconditions expressed in URL mappings. 5      * @param handler the handler object to validate 6      * @param request current HTTP request 7      * @throws Exception if validation failed 8      */ 9     protected void validateHandler(Object handler, HttpServletRequest request) throws Exception {10     }

 

封装handler为HandlerExecutionChain,并添加PathExposingHandlerInterceptor和UriTemplateVariablesHandlerInterceptor拦截器.

1     /** 2      * Build a handler object for the given raw handler, exposing the actual 3      * handler, the {
    @link #PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE}, as well as 4      * the {
    @link #URI_TEMPLATE_VARIABLES_ATTRIBUTE} before executing the handler. 5      * 
The default implementation builds a {
    @link HandlerExecutionChain} 6      * with a special interceptor that exposes the path attribute and uri template variables 7      * @param rawHandler the raw handler to expose 8      * @param pathWithinMapping the path to expose before executing the handler 9      * @param uriTemplateVariables the URI template variables, can be {
    @code null} if no variables found10      * @return the final handler object11      */12     protected Object buildPathExposingHandler(Object rawHandler, String bestMatchingPattern,13             String pathWithinMapping, Map
      
        uriTemplateVariables) {14 15         HandlerExecutionChain chain = new HandlerExecutionChain(rawHandler);16         chain.addInterceptor(new PathExposingHandlerInterceptor(bestMatchingPattern, pathWithinMapping));17         if (!CollectionUtils.isEmpty(uriTemplateVariables)) {18             chain.addInterceptor(new UriTemplateVariablesHandlerInterceptor(uriTemplateVariables));19         }20         return chain;21     }