[Java知识库]Spring MVC源码分析3-请求处理

这篇续上篇，展示请求处理中根据url获取处理器

根据url获取处理器

//private final Map<String, Object> handlerMap = new LinkedHashMap<>();
	protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception {
		// 从缓存中获取处理器
		Object handler = this.handlerMap.get(urlPath);
		if (handler != null) {
			// 判断是beanName还是处理器，如果是beanName，则获取此beanName的Bean
			if (handler instanceof String) {
				String handlerName = (String) handler;
				handler = obtainApplicationContext().getBean(handlerName);
			}
			validateHandler(handler, request);
			return buildPathExposingHandler(handler, urlPath, urlPath, null);
		}

		// 格式匹配
		List<String> 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;
		//获取格式比较器
		Comparator<String> patternComparator = getPathMatcher().getPatternComparator(urlPath);
		if (!matchingPatterns.isEmpty()) {
			//对格式匹配的 url 进行排序
			Collections.sort(matchingPatterns, patternComparator);
			if (logger.isDebugEnabled()) {
				logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns);
			}
			//排序后获得第一个
			bestMatch = matchingPatterns.get(0);
		}
		if (bestMatch != null) {
			//获取处理器
			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 + "]");
				}
			}
			// 判断是beanName还是处理器，如果是beanName，则获取此beanName的Bean
			if (handler instanceof String) {
				String handlerName = (String) handler;
				handler = obtainApplicationContext().getBean(handlerName);
			}
			validateHandler(handler, request);
			//获取匹配的url
			String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestMatch, urlPath);

			// 可能有很多匹配，找到正确的匹配
			Map<String, String> uriTemplateVariables = new LinkedHashMap<>();
			for (String matchingPattern : matchingPatterns) {
				if (patternComparator.compare(bestMatch, matchingPattern) == 0) {
					Map<String, String> vars = getPathMatcher().extractUriTemplateVariables(matchingPattern, urlPath);
					Map<String, String> decodedVars = getUrlPathHelper().decodePathVariables(request, vars);
					uriTemplateVariables.putAll(decodedVars);
				}
			}
			if (logger.isDebugEnabled()) {
				logger.debug("URI Template variables for request [" + urlPath + "] are " + uriTemplateVariables);
			}
			//构建url的处理器链并返回
			return buildPathExposingHandler(handler, bestMatch, pathWithinMapping, uriTemplateVariables);
		}

		// No handler found...
		return null;
	}

构建url的处理器链并返回

protected Object buildPathExposingHandler(Object rawHandler, String bestMatchingPattern,
			String pathWithinMapping, @Nullable Map<String, String> uriTemplateVariables) {

		HandlerExecutionChain chain = new HandlerExecutionChain(rawHandler);
		chain.addInterceptor(new PathExposingHandlerInterceptor(bestMatchingPattern, pathWithinMapping));
		if (!CollectionUtils.isEmpty(uriTemplateVariables)) {
			chain.addInterceptor(new UriTemplateVariablesHandlerInterceptor(uriTemplateVariables));
		}
		return chain;
	}

路径格式匹配

//AntPathMatcher#match
	public boolean match(String pattern, String path) {
		return doMatch(pattern, path, true, null);
	}
	//pathSeparator = "/"
	protected boolean doMatch(String pattern, String path, boolean fullMatch,
			@Nullable Map<String, String> uriTemplateVariables) {
		//上个方法中for循环，匹配，首先匹配 / 
		if (path.startsWith(this.pathSeparator) != pattern.startsWith(this.pathSeparator)) {
			return false;
		}

		String[] pattDirs = tokenizePattern(pattern);
		if (fullMatch && this.caseSensitive && !isPotentialMatch(path, pattDirs)) {
			return false;
		}

		String[] pathDirs = tokenizePath(path);

		int pattIdxStart = 0;
		int pattIdxEnd = pattDirs.length - 1;
		int pathIdxStart = 0;
		int pathIdxEnd = pathDirs.length - 1;

		// Match all elements up to the first **
		while (pattIdxStart <= pattIdxEnd && pathIdxStart <= pathIdxEnd) {
			String pattDir = pattDirs[pattIdxStart];
			if ("**".equals(pattDir)) {
				break;
			}
			if (!matchStrings(pattDir, pathDirs[pathIdxStart], uriTemplateVariables)) {
				return false;
			}
			pattIdxStart++;
			pathIdxStart++;
		}

		if (pathIdxStart > pathIdxEnd) {
			// Path is exhausted, only match if rest of pattern is * or **'s
			if (pattIdxStart > pattIdxEnd) {
				return (pattern.endsWith(this.pathSeparator) == path.endsWith(this.pathSeparator));
			}
			if (!fullMatch) {
				return true;
			}
			if (pattIdxStart == pattIdxEnd && pattDirs[pattIdxStart].equals("*") && path.endsWith(this.pathSeparator)) {
				return true;
			}
			for (int i = pattIdxStart; i <= pattIdxEnd; i++) {
				if (!pattDirs[i].equals("**")) {
					return false;
				}
			}
			return true;
		}
		else if (pattIdxStart > pattIdxEnd) {
			// String not exhausted, but pattern is. Failure.
			return false;
		}
		else if (!fullMatch && "**".equals(pattDirs[pattIdxStart])) {
			// Path start definitely matches due to "**" part in pattern.
			return true;
		}

		// up to last '**'
		while (pattIdxStart <= pattIdxEnd && pathIdxStart <= pathIdxEnd) {
			String pattDir = pattDirs[pattIdxEnd];
			if (pattDir.equals("**")) {
				break;
			}
			if (!matchStrings(pattDir, pathDirs[pathIdxEnd], uriTemplateVariables)) {
				return false;
			}
			pattIdxEnd--;
			pathIdxEnd--;
		}
		if (pathIdxStart > pathIdxEnd) {
			// String is exhausted
			for (int i = pattIdxStart; i <= pattIdxEnd; i++) {
				if (!pattDirs[i].equals("**")) {
					return false;
				}
			}
			return true;
		}

		while (pattIdxStart != pattIdxEnd && pathIdxStart <= pathIdxEnd) {
			int patIdxTmp = -1;
			for (int i = pattIdxStart + 1; i <= pattIdxEnd; i++) {
				if (pattDirs[i].equals("**")) {
					patIdxTmp = i;
					break;
				}
			}
			if (patIdxTmp == pattIdxStart + 1) {
				// '**/**' situation, so skip one
				pattIdxStart++;
				continue;
			}
			// Find the pattern between padIdxStart & padIdxTmp in str between
			// strIdxStart & strIdxEnd
			int patLength = (patIdxTmp - pattIdxStart - 1);
			int strLength = (pathIdxEnd - pathIdxStart + 1);
			int foundIdx = -1;

			strLoop:
			for (int i = 0; i <= strLength - patLength; i++) {
				for (int j = 0; j < patLength; j++) {
					String subPat = pattDirs[pattIdxStart + j + 1];
					String subStr = pathDirs[pathIdxStart + i + j];
					if (!matchStrings(subPat, subStr, uriTemplateVariables)) {
						continue strLoop;
					}
				}
				foundIdx = pathIdxStart + i;
				break;
			}

			if (foundIdx == -1) {
				return false;
			}

			pattIdxStart = patIdxTmp;
			pathIdxStart = foundIdx + patLength;
		}

		for (int i = pattIdxStart; i <= pattIdxEnd; i++) {
			if (!pattDirs[i].equals("**")) {
				return false;
			}
		}

		return true;
	}

protected String[] tokenizePattern(String pattern) {
		String[] tokenized = null;
		Boolean cachePatterns = this.cachePatterns;
		if (cachePatterns == null || cachePatterns.booleanValue()) {
			tokenized = this.tokenizedPatternCache.get(pattern);
		}
		if (tokenized == null) {
			tokenized = tokenizePath(pattern);
			if (cachePatterns == null && this.tokenizedPatternCache.size() >= CACHE_TURNOFF_THRESHOLD) {
				// Try to adapt to the runtime situation that we're encountering:
				// There are obviously too many different patterns coming in here...
				// So let's turn off the cache since the patterns are unlikely to be reoccurring.
				deactivatePatternCache();
				return tokenized;
			}
			if (cachePatterns == null || cachePatterns.booleanValue()) {
				this.tokenizedPatternCache.put(pattern, tokenized);
			}
		}
		return tokenized;
	}
	protected String[] tokenizePath(String path) {
		return StringUtils.tokenizeToStringArray(path, this.pathSeparator, this.trimTokens, true);
	}