springMVC源码分析--AbstractHandlerMethodMapping获取url和HandlerMethod对应关系（十）

在之前的博客 springMVC源码分析--AbstractHandlerMapping（二）中我们介绍了AbstractHandlerMethodMapping的父类AbstractHandlerMapping，其定义了抽象方法getHandlerInternal(HttpServletRequest request)，我看一下其在AbstractHandlerMethodMapping中的实现。

在AbstractHandlerMethodMapping中getHandlerInternal的实现如下：

//根据request来获取HandlerMethod@Overrideprotected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {//获取请求连接String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);if (logger.isDebugEnabled()) {logger.debug("Looking up handler method for path " + lookupPath);}//读锁this.mappingRegistry.acquireReadLock();try {//获取HandlerMethodHandlerMethod 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 + "]");}}return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);}finally {this.mappingRegistry.releaseReadLock();}}

具体的实现是在lookupHandlerMethod中，最终是在mappingRegistry中获取HandlerMethod，mappingRegistry可以看似是一个Map结构（其实其包含了3个map），包含了url和HandlerMethod的对应关系。

protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {List<Match> matches = new ArrayList<Match>();//从mappingRegistry中获取directPathMatches匹配关系List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);if (directPathMatches != null) {addMatchingMappings(directPathMatches, matches, request);}if (matches.isEmpty()) {// No choice but to go through all mappings...addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);}//最终返回HandlerMethodif (!matches.isEmpty()) {Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));Collections.sort(matches, comparator);if (logger.isTraceEnabled()) {logger.trace("Found " + matches.size() + " matching mapping(s) for [" +lookupPath + "] : " + matches);}Match bestMatch = matches.get(0);if (matches.size() > 1) {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 + "}");}}handleMatch(bestMatch.mapping, lookupPath, request);return bestMatch.handlerMethod;}else {return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);}}

以下几个方法是在查找url和HandlerMethod的过程中一些帮助实现。

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)));}}}//在子类中实现protected abstract T getMatchingMapping(T mapping, HttpServletRequest request);protected abstract Comparator<T> getMappingComparator(HttpServletRequest request);protected void handleMatch(T mapping, String lookupPath, HttpServletRequest request) {request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, lookupPath);}//在子类中实现protected HandlerMethod handleNoMatch(Set<T> mappings, String lookupPath, HttpServletRequest request)throws Exception {return null;}