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

超、凢脫俗 2022-07-13 02:59 116阅读 0赞

在之前的博客[ springMVC源码分析--AbstractHandlerMapping（二）][springMVC_--AbstractHandlerMapping]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。

![Image 1][]

在AbstractHandlerMethodMapping中getHandlerInternal的实现如下：

//根据request来获取HandlerMethod
    	@Override
    	protected 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HandlerMethod
    			HandlerMethod 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HandlerMethod
    		if (!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;
    	}

[springMVC_--AbstractHandlerMapping]: http://blog.csdn.net/qq924862077/article/details/53747152
[Image 1]: