SpringMVC源码情操陶冶-AbstractHandlerMapping

分析下springmvc的HandlerMapping映射的抽象类

初始化操作

通过initApplicationContext()方法进行初始化，其一般是由父类执行ApplicationContextAware#setApplicationContext()方法间接调用，源码奉上

	protected void initApplicationContext() throws BeansException {
		//供子类扩展添加拦截器，目前spring没有自行实现
		extendInterceptors(this.interceptors);
		//搜寻springmvc中的MappedInterceptors保存至adaptedInterceptors集合
		detectMappedInterceptors(this.adaptedInterceptors);
		//将interceptors集合添加至adaptedInterceptors集合中
		initInterceptors();
	}

主要目的是获取springmvc上下文中的拦截器集合，此处特指MappedInterceptor

AbstractHandlerMapping#getHandler()-获取处理链对象

源码奉上

	public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
		//getHandlerInternal(request)方法为抽象方法，供子类实现
		//获取到的handler对象一般为bean/HandlerMethod
		Object handler = getHandlerInternal(request);
		//上述找不到则使用默认的处理类，没有设定则返回null，则会返回前台404错误
		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);
		}
		//创建处理链对象
		HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
		//针对cros跨域请求的处理，此处就不分析了
		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;
	}

由以上代码分析可知，需要观察下如何获取handler对象以及创建HandlerExecutionChain处理链对象

AbstractHandlerMethodMapping#getHandlerInternal()-针对HandlerMethod的获取

主要是解析@Controller注解类中的@RequestMapping方法得到其中的HandlerMethod对象作为返回的Handler

	protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
		//获取访问的路径，一般类似于request.getServletPath()返回不含contextPath的访问路径
		String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
		
		//获取读锁
		this.mappingRegistry.acquireReadLock();
		try {
			//获取HandlerMethod作为handler对象,这里涉及到路径匹配的优先级
			//优先级：精确匹配>最长路径匹配>扩展名匹配
			HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
			//HandlerMethod内部含有bean对象，其实指的是对应的Controller
			return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
		}
		finally {
			//释放读锁
			this.mappingRegistry.releaseReadLock();
		}
	}

AbstractUrlHandlerMapping#getHandlerInternal()-针对beanName的获取

源码奉上，此处的逻辑就较为简单了

	protected Object getHandlerInternal(HttpServletRequest request) throws Exception {
		String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
		//从handlerMap查找路径对应的beanName
		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);
			}
		}
		
		return handler;
	}

AbstractHandlerMapping#getHandlerExecutionChain()-创建处理链对象

先附上HandlerExecutionChain的内部属性

        //真实处理请求对象
	private final Object handler;
        
        //拦截器集合
	private HandlerInterceptor[] interceptors;
        
        //拦截器集合
	private List<HandlerInterceptor> interceptorList;
        
        //拦截器开始下标，默认正序执行
	private int interceptorIndex = -1;

再奉上创建处理链对象的源码

	//此处的handler可为HandlerMethod/beanName
	protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
		HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
				(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));

		String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
		for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
			if (interceptor instanceof MappedInterceptor) {
				MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
				if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
					chain.addInterceptor(mappedInterceptor.getInterceptor());
				}
			}
			else {
				chain.addInterceptor(interceptor);
			}
		}
		return chain;
	}

处理链的创建基本就是 带有handler对象以及添加拦截器对象集合，用于后期的拦截

• HandlerExecutionChain处理链内部含有handler对象，可为@RequestMapping对应的HandlerMethod对象，也可为springmvc上下文的beanName

• HandlerExecutionChain处理链内部主要包含拦截器对象，其可从springmvc上下文获取HandlerInterceptor/MappedHandlerInterceptor类型作为内部集合；
  当然此处获得拦截器集合也是根据路径匹配获取的，比如mvc:interceptor指定的或者mvc:resource指定的

小结