springMVC源码分析--AbstractUrlHandlerMapping(三)
上一篇博客springMVC源码分析--AbstractHandlerMapping(二)中我们介绍了AbstractHandlerMapping了,接下来我们介绍其子类AbstractUrlHandlerMapping。
在上一篇博客中我们了解到AbstractHandlerMapping提供了一个抽象类getHandlerInternal(HttpServletRequest request),我们首先看看AbstractUrlHandlerMapping中对抽象类getHandlerInternal(HttpServletRequest request)的实现。
//获取Handler,主要是通过url和method的对应关系来查找 @Override protected Object getHandlerInternal(HttpServletRequest request) throws Exception { //获取request中的请求链接 String lookupPath = getUrlPathHelper().getLookupPathForRequest(request); //根据链接查找handler 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. //定义一个变量,保存找到的原始Handler Object rawHandler = null; if ("/".equals(lookupPath)) { rawHandler = getRootHandler(); } if (rawHandler == null) { rawHandler = getDefaultHandler(); } if (rawHandler != null) { // Bean name or resolved handler? //如果是String类型则到容器中查找具体的Bean 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; }
从上面的实现方法getHandlerInternal来看,首先是通过lookupHandler方法来查找Handler,这里我们看到了之前说的Map对象,用来存储url和Handler之间的关系,当Handler获取为String时需要从Bean容器中获取注入的实现类,当然在查找过程中也会有模糊匹配等查找过程。
protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception { // Direct match? //直接从map中获取 Object handler = this.handlerMap.get(urlPath); if (handler != null) { // Bean name or resolved handler? //如果是String类型则从容器中获取 if (handler instanceof String) { String handlerName = (String) handler; handler = getApplicationContext().getBean(handlerName); } validateHandler(handler, request); return buildPathExposingHandler(handler, urlPath, urlPath, null); } // Pattern match? //通过模糊匹配来查找 List<String> matchingPatterns = new ArrayList<String>(); 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 bestPatternMatch = null; //匹配规则 Comparator<String> patternComparator = getPathMatcher().getPatternComparator(urlPath); if (!matchingPatterns.isEmpty()) { Collections.sort(matchingPatterns, patternComparator); if (logger.isDebugEnabled()) { logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns); } bestPatternMatch = matchingPatterns.get(0); } if (bestPatternMatch != null) { handler = this.handlerMap.get(bestPatternMatch); if (handler == null) { Assert.isTrue(bestPatternMatch.endsWith("/")); handler = this.handlerMap.get(bestPatternMatch.substring(0, bestPatternMatch.length() - 1)); } // Bean name or resolved handler? if (handler instanceof String) { String handlerName = (String) handler; handler = getApplicationContext().getBean(handlerName); } validateHandler(handler, request); String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestPatternMatch, urlPath); // There might be multiple 'best patterns', let's make sure we have the correct URI template variables // for all of them Map<String, String> uriTemplateVariables = new LinkedHashMap<String, String>(); for (String matchingPattern : matchingPatterns) { if (patternComparator.compare(bestPatternMatch, 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); } return buildPathExposingHandler(handler, bestPatternMatch, pathWithinMapping, uriTemplateVariables); } // No handler found... return null; }
上面两个方法介绍了通过url来查找handlerMap获取handler的操作,AbstractUrlHandlerMapping中也提供了注册url和handler到handlerMap中的操作,具体的调用则要到AbstractUrlHandlerMapping的子类中实现。
//注册url和Bean的map,注册多个string的url到一个处理器中 protected void registerHandler(String[] urlPaths, String beanName) throws BeansException, IllegalStateException { Assert.notNull(urlPaths, "URL path array must not be null"); for (String urlPath : urlPaths) { registerHandler(urlPath, beanName); } } ////注册url和Bean的map,将具体的Handler注入到url对应的map中 protected void registerHandler(String urlPath, Object handler) throws BeansException, IllegalStateException { Assert.notNull(urlPath, "URL path must not be null"); Assert.notNull(handler, "Handler object must not be null"); Object resolvedHandler = handler; // Eagerly resolve handler if referencing singleton via name. //如果Handler是String类型而且没有设置lazyInitHandlers则从springMVC容器中获取handler if (!this.lazyInitHandlers && handler instanceof String) { String handlerName = (String) handler; if (getApplicationContext().isSingleton(handlerName)) { resolvedHandler = getApplicationContext().getBean(handlerName); } } Object mappedHandler = this.handlerMap.get(urlPath); if (mappedHandler != null) { if (mappedHandler != resolvedHandler) { throw new IllegalStateException( "Cannot map " + getHandlerDescription(handler) + " to URL path [" + urlPath + "]: There is already " + getHandlerDescription(mappedHandler) + " mapped."); } } else { if (urlPath.equals("/")) { if (logger.isInfoEnabled()) { logger.info("Root mapping to " + getHandlerDescription(handler)); } setRootHandler(resolvedHandler); } else if (urlPath.equals("/*")) { if (logger.isInfoEnabled()) { logger.info("Default mapping to " + getHandlerDescription(handler)); } setDefaultHandler(resolvedHandler); } else { this.handlerMap.put(urlPath, resolvedHandler); if (logger.isInfoEnabled()) { logger.info("Mapped URL path [" + urlPath + "] onto " + getHandlerDescription(handler)); } } } }
通过上面介绍我们知道AbstractUrlHandlerMapping提供的功能就是根据url从handlerMap中获取handler和注册url和handler的对应关系到handlerMap中,当然这个过程中还包含很多其他的操作。
AbstractUrlHandlerMapping的完整源码如下:
public abstract class AbstractUrlHandlerMapping extends AbstractHandlerMapping { private Object rootHandler; private boolean useTrailingSlashMatch = false; private boolean lazyInitHandlers = false; private final Map<String, Object> handlerMap = new LinkedHashMap<String, Object>(); public void setRootHandler(Object rootHandler) { this.rootHandler = rootHandler; } public Object getRootHandler() { return this.rootHandler; } public void setUseTrailingSlashMatch(boolean useTrailingSlashMatch) { this.useTrailingSlashMatch = useTrailingSlashMatch; } public boolean useTrailingSlashMatch() { return this.useTrailingSlashMatch; } public void setLazyInitHandlers(boolean lazyInitHandlers) { this.lazyInitHandlers = lazyInitHandlers; } //获取Handler,主要是通过url和method的对应关系来查找 @Override protected Object getHandlerInternal(HttpServletRequest request) throws Exception { //获取request中的请求链接 String lookupPath = getUrlPathHelper().getLookupPathForRequest(request); //根据链接查找handler 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. //定义一个变量,保存找到的原始Handler Object rawHandler = null; if ("/".equals(lookupPath)) { rawHandler = getRootHandler(); } if (rawHandler == null) { rawHandler = getDefaultHandler(); } if (rawHandler != null) { // Bean name or resolved handler? //如果是String类型则到容器中查找具体的Bean 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; } protected Object lookupHandler(String urlPath, HttpServletRequest request) throws Exception { // Direct match? //直接从map中获取 Object handler = this.handlerMap.get(urlPath); if (handler != null) { // Bean name or resolved handler? //如果是String类型则从容器中获取 if (handler instanceof String) { String handlerName = (String) handler; handler = getApplicationContext().getBean(handlerName); } validateHandler(handler, request); return buildPathExposingHandler(handler, urlPath, urlPath, null); } // Pattern match? //通过模糊匹配来查找 List<String> matchingPatterns = new ArrayList<String>(); 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 bestPatternMatch = null; //匹配规则 Comparator<String> patternComparator = getPathMatcher().getPatternComparator(urlPath); if (!matchingPatterns.isEmpty()) { Collections.sort(matchingPatterns, patternComparator); if (logger.isDebugEnabled()) { logger.debug("Matching patterns for request [" + urlPath + "] are " + matchingPatterns); } bestPatternMatch = matchingPatterns.get(0); } if (bestPatternMatch != null) { handler = this.handlerMap.get(bestPatternMatch); if (handler == null) { Assert.isTrue(bestPatternMatch.endsWith("/")); handler = this.handlerMap.get(bestPatternMatch.substring(0, bestPatternMatch.length() - 1)); } // Bean name or resolved handler? if (handler instanceof String) { String handlerName = (String) handler; handler = getApplicationContext().getBean(handlerName); } validateHandler(handler, request); String pathWithinMapping = getPathMatcher().extractPathWithinPattern(bestPatternMatch, urlPath); // There might be multiple 'best patterns', let's make sure we have the correct URI template variables // for all of them Map<String, String> uriTemplateVariables = new LinkedHashMap<String, String>(); for (String matchingPattern : matchingPatterns) { if (patternComparator.compare(bestPatternMatch, 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); } return buildPathExposingHandler(handler, bestPatternMatch, pathWithinMapping, uriTemplateVariables); } // No handler found... return null; } protected void validateHandler(Object handler, HttpServletRequest request) throws Exception { } //用于给找到的Handler注册两个拦截器PathExposingHandlerInterceptor和UriTemplateVariablesHandlerInterceptor //这两个拦截器的的作用是将与当前url实际匹配的Pattern、匹配条件和url模板参数设置到request的属性中 protected Object buildPathExposingHandler(Object rawHandler, String bestMatchingPattern, String pathWithinMapping, 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; } protected void exposePathWithinMapping(String bestMatchingPattern, String pathWithinMapping, HttpServletRequest request) { request.setAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE, bestMatchingPattern); request.setAttribute(HandlerMapping.PATH_WITHIN_HANDLER_MAPPING_ATTRIBUTE, pathWithinMapping); } protected void exposeUriTemplateVariables(Map<String, String> uriTemplateVariables, HttpServletRequest request) { request.setAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, uriTemplateVariables); } //注册url和Bean的map,注册多个string的url到一个处理器中 protected void registerHandler(String[] urlPaths, String beanName) throws BeansException, IllegalStateException { Assert.notNull(urlPaths, "URL path array must not be null"); for (String urlPath : urlPaths) { registerHandler(urlPath, beanName); } } ////注册url和Bean的map,将具体的Handler注入到url对应的map中 protected void registerHandler(String urlPath, Object handler) throws BeansException, IllegalStateException { Assert.notNull(urlPath, "URL path must not be null"); Assert.notNull(handler, "Handler object must not be null"); Object resolvedHandler = handler; // Eagerly resolve handler if referencing singleton via name. //如果Handler是String类型而且没有设置lazyInitHandlers则从springMVC容器中获取handler if (!this.lazyInitHandlers && handler instanceof String) { String handlerName = (String) handler; if (getApplicationContext().isSingleton(handlerName)) { resolvedHandler = getApplicationContext().getBean(handlerName); } } Object mappedHandler = this.handlerMap.get(urlPath); if (mappedHandler != null) { if (mappedHandler != resolvedHandler) { throw new IllegalStateException( "Cannot map " + getHandlerDescription(handler) + " to URL path [" + urlPath + "]: There is already " + getHandlerDescription(mappedHandler) + " mapped."); } } else { if (urlPath.equals("/")) { if (logger.isInfoEnabled()) { logger.info("Root mapping to " + getHandlerDescription(handler)); } setRootHandler(resolvedHandler); } else if (urlPath.equals("/*")) { if (logger.isInfoEnabled()) { logger.info("Default mapping to " + getHandlerDescription(handler)); } setDefaultHandler(resolvedHandler); } else { this.handlerMap.put(urlPath, resolvedHandler); if (logger.isInfoEnabled()) { logger.info("Mapped URL path [" + urlPath + "] onto " + getHandlerDescription(handler)); } } } } private String getHandlerDescription(Object handler) { return "handler " + (handler instanceof String ? "'" + handler + "'" : "of type [" + handler.getClass() + "]"); } public final Map<String, Object> getHandlerMap() { return Collections.unmodifiableMap(this.handlerMap); } protected boolean supportsTypeLevelMappings() { return false; } 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(HandlerMapping.INTROSPECT_TYPE_LEVEL_MAPPING, supportsTypeLevelMappings()); return true; } } private class UriTemplateVariablesHandlerInterceptor extends HandlerInterceptorAdapter { private final Map<String, String> uriTemplateVariables; public UriTemplateVariablesHandlerInterceptor(Map<String, String> uriTemplateVariables) { this.uriTemplateVariables = uriTemplateVariables; } @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) { exposeUriTemplateVariables(this.uriTemplateVariables, request); return true; } } }
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