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