spring mvc如何计算BEST_MATCHING_PATTERN

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本文主要研究一下spring mvc如何计算best-matching-pattern

DispatcherServlet

spring-webmvc-4.3.10.RELEASE-sources.jar!/org/springframework/web/servlet/DispatcherServlet.java

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 {                processedRequest = checkMultipart(request);                multipartRequestParsed = (processedRequest != request);                // Determine handler for the current request.                mappedHandler = getHandler(processedRequest);                if (mappedHandler == null || mappedHandler.getHandler() == null) {                    noHandlerFound(processedRequest, response);                    return;                }                // Determine handler adapter for the current request.                HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());                // Process last-modified header, if supported by the handler.                String method = request.getMethod();                boolean isGet = "GET".equals(method);                if (isGet || "HEAD".equals(method)) {                    long lastModified = ha.getLastModified(request, mappedHandler.getHandler());                    if (logger.isDebugEnabled()) {                        logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);                    }                    if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {                        return;                    }                }                if (!mappedHandler.applyPreHandle(processedRequest, response)) {                    return;                }                // Actually invoke the handler.                mv = ha.handle(processedRequest, response, mappedHandler.getHandler());                if (asyncManager.isConcurrentHandlingStarted()) {                    return;                }                applyDefaultViewName(processedRequest, mv);                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);            }            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);                }            }        }    }复制代码

主要看mappedHandler = getHandler(processedRequest);这段

/**     * Return the HandlerExecutionChain for this request.     * Tries all handler mappings in order.     * @param request current HTTP request     * @return the HandlerExecutionChain, or {@code null} if no handler could be found     */    protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {        for (HandlerMapping hm : this.handlerMappings) {            if (logger.isTraceEnabled()) {                logger.trace(                        "Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");            }            HandlerExecutionChain handler = hm.getHandler(request);            if (handler != null) {                return handler;            }        }        return null;    }复制代码

这里的handlerMappings主要有：

SimpleUrlHandlerMapping

EndpointHandlerMapping

ReuqestMappingHandlerMapping

BeanNameUrlHandlerMapping

WebMvcConfigurationSupport$EmptyHandlerMapping

主要有抽象类AbstractHandlerMapping来执行

AbstractHandlerMapping#getHandler

spring-webmvc-4.3.10.RELEASE-sources.jar!/org/springframework/web/servlet/handler/AbstractHandlerMapping.java

/**     * 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    public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {        Object handler = getHandlerInternal(request);        if (handler == null) {            handler = getDefaultHandler();        }        if (handler == null) {            return null;        }        // Bean name or resolved handler?        if (handler instanceof String) {            String handlerName = (String) handler;            handler = getApplicationContext().getBean(handlerName);        }        HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);        if (CorsUtils.isCorsRequest(request)) {            CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);            CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);            CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);            executionChain = getCorsHandlerExecutionChain(request, executionChain, config);        }        return executionChain;    }复制代码

这里主要看Object handler = getHandlerInternal(request);这段

AbstractUrlHandlerMapping#getHandlerInternal

spring-webmvc-4.3.12.RELEASE-sources.jar!/org/springframework/web/servlet/handler/AbstractUrlHandlerMapping.java

/**     * Look up a handler for the URL path of the given request.     * @param request current HTTP request     * @return the handler instance, or {@code null} if none found     */    @Override    protected Object getHandlerInternal(HttpServletRequest request) throws Exception {        String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);        Object handler = lookupHandler(lookupPath, request);        if (handler == null) {            // We need to care for the default handler directly, since we need to            // expose the PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE for it as well.            Object rawHandler = null;            if ("/".equals(lookupPath)) {                rawHandler = getRootHandler();            }            if (rawHandler == null) {                rawHandler = getDefaultHandler();            }            if (rawHandler != null) {                // Bean name or resolved handler?                if (rawHandler instanceof String) {                    String handlerName = (String) rawHandler;                    rawHandler = getApplicationContext().getBean(handlerName);                }                validateHandler(rawHandler, request);                handler = buildPathExposingHandler(rawHandler, lookupPath, lookupPath, null);            }        }        if (handler != null && logger.isDebugEnabled()) {            logger.debug("Mapping [" + lookupPath + "] to " + handler);        }        else if (handler == null && logger.isTraceEnabled()) {            logger.trace("No handler mapping found for [" + lookupPath + "]");        }        return handler;    }复制代码

这里主要看lookupHandler

AbstractUrlHandlerMapping#lookupHandler

spring-webmvc-4.3.12.RELEASE-sources.jar!/org/springframework/web/servlet/handler/AbstractUrlHandlerMapping.java

protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {        // Direct match?        Object handler = this.handlerMap.get(urlPath);        if (handler != null) {            // Bean name or resolved handler?            if (handler instanceof String) {                String handlerName = (String) handler;                handler = getApplicationContext().getBean(handlerName);            }            validateHandler(handler, request);            return buildPathExposingHandler(handler, urlPath, urlPath, null);        }        // Pattern match?        List
    
      matchingPatterns = new ArrayList
     
      ();        for (String registeredPattern : this.handlerMap.keySet()) {            if (getPathMatcher().match(registeredPattern, urlPath)) {                matchingPatterns.add(registeredPattern);            }            else if (useTrailingSlashMatch()) {                if (!registeredPattern.endsWith("/") && getPathMatcher().match(registeredPattern + "/", urlPath)) {                    matchingPatterns.add(registeredPattern +"/");                }            }        }        String bestMatch = null;        Comparator
      
        patternComparator = getPathMatcher().getPatternComparator(urlPath);        if (!matchingPatterns.isEmpty()) {            Collections.sort(matchingPatterns, patternComparator);            if (logger.isDebugEnabled()) {                logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);            }            bestMatch = matchingPatterns.get(0);        }        if (bestMatch != null) {            handler = this.handlerMap.get(bestMatch);            if (handler == null) {                if (bestMatch.endsWith("/")) {                    handler = this.handlerMap.get(bestMatch.substring(0, bestMatch.length() - 1));                }                if (handler == null) {                    throw new IllegalStateException(                            "Could not find handler for best pattern match [" + bestMatch + "]");                }            }            // Bean name or resolved handler?            if (handler instanceof String) {                String handlerName = (String) handler;                handler = getApplicationContext().getBean(handlerName);            }            validateHandler(handler, request);            String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestMatch, urlPath);            // There might be multiple 'best patterns', let's make sure we have the correct URI template variables            // for all of them            Map
       
         uriTemplateVariables = new LinkedHashMap
        
         ();            for (String matchingPattern : matchingPatterns) {                if (patternComparator.compare(bestMatch, matchingPattern) == 0) {                    Map
         
           vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath); Map
          
            decodedVars = getUrlPathHelper().decodePathVariables(request, vars); uriTemplateVariables.putAll(decodedVars); } } if (logger.isDebugEnabled()) { logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables); } return buildPathExposingHandler(handler, bestMatch, pathWithinMapping, uriTemplateVariables); } // No handler found... return null; }复制代码

这里就是bestMatch计算的核心

设置

计算完bestMatch之后，就是设置，主要是调用AbstractUrlHandlerMapping#buildPathExposingHandler

/**     * Build a handler object for the given raw handler, exposing the actual     * handler, the {@link #PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE}, as well as     * the {@link #URI_TEMPLATE_VARIABLES_ATTRIBUTE} before executing the handler.     * The default implementation builds a {@link HandlerExecutionChain}     * with a special interceptor that exposes the path attribute and uri template variables     * @param rawHandler the raw handler to expose     * @param pathWithinMapping the path to expose before executing the handler     * @param uriTemplateVariables the URI template variables, can be {@code null} if no variables found     * @return the final handler object     */    protected Object buildPathExposingHandler(Object rawHandler, String bestMatchingPattern,            String pathWithinMapping, Map
     
       uriTemplateVariables) {        HandlerExecutionChain chain = new HandlerExecutionChain(rawHandler);        chain.addInterceptor(new PathExposingHandlerInterceptor(bestMatchingPattern, pathWithinMapping));        if (!CollectionUtils.isEmpty(uriTemplateVariables)) {            chain.addInterceptor(new UriTemplateVariablesHandlerInterceptor(uriTemplateVariables));        }        return chain;    }复制代码

而这个方法，new了一个PathExposingHandlerInterceptor

/**     * Special interceptor for exposing the     * {@link AbstractUrlHandlerMapping#PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE} attribute.     * @see AbstractUrlHandlerMapping#exposePathWithinMapping     */    private class PathExposingHandlerInterceptor extends HandlerInterceptorAdapter {        private final String bestMatchingPattern;        private final String pathWithinMapping;        public PathExposingHandlerInterceptor(String bestMatchingPattern, String pathWithinMapping) {            this.bestMatchingPattern = bestMatchingPattern;            this.pathWithinMapping = pathWithinMapping;        }        @Override        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {            exposePathWithinMapping(this.bestMatchingPattern, this.pathWithinMapping, request);            request.setAttribute(INTROSPECT_TYPE_LEVEL_MAPPING, supportsTypeLevelMappings());            return true;        }    }    /**     * Expose the path within the current mapping as request attribute.     * @param pathWithinMapping the path within the current mapping     * @param request the request to expose the path to     * @see #PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE     */    protected void exposePathWithinMapping(String bestMatchingPattern, String pathWithinMapping, HttpServletRequest request) {        request.setAttribute(BEST_MATCHING_PATTERN_ATTRIBUTE, bestMatchingPattern);        request.setAttribute(PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, pathWithinMapping);    }复制代码

可以看到，这里通过exposePathWithinMapping方法设置了BEST_MATCHING_PATTERN_ATTRIBUTE