springMVC源码分析--拦截器HandlerExecutionChain（三）

上一篇博客springMVC源码分析--HandlerInterceptor拦截器调用过程（二）中我们介绍了HandlerInterceptor的执行调用地方，最终HandlerInterceptor调用的地方是在HandlerExecutionChain中，接下来我们就介绍一下HandlerExecutionChain。HandlerExecutionChain有3个变量：

Object handler；不做过多介绍，存储的对象是HandlerMethod

HandlerInterceptor[] interceptors ：所有的HandlerInterceptor的数组

List<HandlerInterceptor> interceptorList：所有的HandlerInterceptor的链表

之前的博客中我们已经介绍了HandlerExecutionChain中执行HandlerInterceptor方法的函数

执行HandlerInterceptor的preHandler方法

/**
	 * Apply preHandle methods of registered interceptors.
	 * @return {@code true} if the execution chain should proceed with the
	 * next interceptor or the handler itself. Else, DispatcherServlet assumes
	 * that this interceptor has already dealt with the response itself.
	 */
	//依次执行HandlerInterceptor实现类的preHandle函数
	boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = 0; i < interceptors.length; i++) {
				HandlerInterceptor interceptor = interceptors[i];
				if (!interceptor.preHandle(request, response, this.handler)) {
					triggerAfterCompletion(request, response, null);
					return false;
				}
				this.interceptorIndex = i;
			}
		}
		return true;
	}

执行HandlerInterceptor实现类的postHandle函数

//依次执行HandlerInterceptor实现类的postHandle函数
	void applyPostHandle(HttpServletRequest request, HttpServletResponse response, ModelAndView mv) throws Exception {
		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = interceptors.length - 1; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				interceptor.postHandle(request, response, this.handler, mv);
			}
		}
	}

执行HandlerInterceptor实现类的afterCompletion函数

//依次执行HandlerInterceptor实现类的postHandle函数
	void applyPostHandle(HttpServletRequest request, HttpServletResponse response, ModelAndView mv) throws Exception {
		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = interceptors.length - 1; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				interceptor.postHandle(request, response, this.handler, mv);
			}
		}
	}

执行HandlerInterceptor实现类的afterCompletion函数

//依次执行HandlerInterceptor实现类的afterCompletion函数
	void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, Exception ex)
			throws Exception {

		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = this.interceptorIndex; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				try {
					interceptor.afterCompletion(request, response, this.handler, ex);
				}
				catch (Throwable ex2) {
					logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
				}
			}
		}
	}

完整的HandlerExecutionChain的源码，主要就是以上几个函数的操作

public class HandlerExecutionChain {

	private static final Log logger = LogFactory.getLog(HandlerExecutionChain.class);

	private final Object handler;

	private HandlerInterceptor[] interceptors;

	private List<HandlerInterceptor> interceptorList;

	private int interceptorIndex = -1;

	public HandlerExecutionChain(Object handler) {
		this(handler, (HandlerInterceptor[]) null);
	}

	public HandlerExecutionChain(Object handler, HandlerInterceptor... interceptors) {
		if (handler instanceof HandlerExecutionChain) {
			HandlerExecutionChain originalChain = (HandlerExecutionChain) handler;
			this.handler = originalChain.getHandler();
			this.interceptorList = new ArrayList<HandlerInterceptor>();
			CollectionUtils.mergeArrayIntoCollection(originalChain.getInterceptors(), this.interceptorList);
			CollectionUtils.mergeArrayIntoCollection(interceptors, this.interceptorList);
		}
		else {
			this.handler = handler;
			this.interceptors = interceptors;
		}
	}

	public Object getHandler() {
		return this.handler;
	}

	public void addInterceptor(HandlerInterceptor interceptor) {
		initInterceptorList().add(interceptor);
	}

	public void addInterceptors(HandlerInterceptor... interceptors) {
		if (!ObjectUtils.isEmpty(interceptors)) {
			initInterceptorList().addAll(Arrays.asList(interceptors));
		}
	}

	private List<HandlerInterceptor> initInterceptorList() {
		if (this.interceptorList == null) {
			this.interceptorList = new ArrayList<HandlerInterceptor>();
			if (this.interceptors != null) {
				// An interceptor array specified through the constructor
				this.interceptorList.addAll(Arrays.asList(this.interceptors));
			}
		}
		this.interceptors = null;
		return this.interceptorList;
	}

	/**
	 * Return the array of interceptors to apply (in the given order).
	 * @return the array of HandlerInterceptors instances (may be {@code null})
	 */
	public HandlerInterceptor[] getInterceptors() {
		if (this.interceptors == null && this.interceptorList != null) {
			this.interceptors = this.interceptorList.toArray(new HandlerInterceptor[this.interceptorList.size()]);
		}
		return this.interceptors;
	}

	/**
	 * Apply preHandle methods of registered interceptors.
	 * @return {@code true} if the execution chain should proceed with the
	 * next interceptor or the handler itself. Else, DispatcherServlet assumes
	 * that this interceptor has already dealt with the response itself.
	 */
	//依次执行HandlerInterceptor实现类的preHandle函数
	boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = 0; i < interceptors.length; i++) {
				HandlerInterceptor interceptor = interceptors[i];
				if (!interceptor.preHandle(request, response, this.handler)) {
					triggerAfterCompletion(request, response, null);
					return false;
				}
				this.interceptorIndex = i;
			}
		}
		return true;
	}

	/**
	 * Apply postHandle methods of registered interceptors.
	 */
	//依次执行HandlerInterceptor实现类的postHandle函数
	void applyPostHandle(HttpServletRequest request, HttpServletResponse response, ModelAndView mv) throws Exception {
		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = interceptors.length - 1; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				interceptor.postHandle(request, response, this.handler, mv);
			}
		}
	}

	//依次执行HandlerInterceptor实现类的afterCompletion函数
	void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, Exception ex)
			throws Exception {

		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = this.interceptorIndex; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				try {
					interceptor.afterCompletion(request, response, this.handler, ex);
				}
				catch (Throwable ex2) {
					logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
				}
			}
		}
	}

	/**
	 * Apply afterConcurrentHandlerStarted callback on mapped AsyncHandlerInterceptors.
	 */
	//这个方法会在Controller方法异步执行时开始执行
	void applyAfterConcurrentHandlingStarted(HttpServletRequest request, HttpServletResponse response) {
		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = interceptors.length - 1; i >= 0; i--) {
				if (interceptors[i] instanceof AsyncHandlerInterceptor) {
					try {
						AsyncHandlerInterceptor asyncInterceptor = (AsyncHandlerInterceptor) interceptors[i];
						asyncInterceptor.afterConcurrentHandlingStarted(request, response, this.handler);
					}
					catch (Throwable ex) {
						logger.error("Interceptor [" + interceptors[i] + "] failed in afterConcurrentHandlingStarted", ex);
					}
				}
			}
		}
	}

	/**
	 * Delegates to the handler's {@code toString()}.
	 */
	@Override
	public String toString() {
		if (this.handler == null) {
			return "HandlerExecutionChain with no handler";
		}
		StringBuilder sb = new StringBuilder();
		sb.append("HandlerExecutionChain with handler [").append(this.handler).append("]");
		if (!CollectionUtils.isEmpty(this.interceptorList)) {
			sb.append(" and ").append(this.interceptorList.size()).append(" interceptor");
			if (this.interceptorList.size() > 1) {
				sb.append("s");
			}
		}
		return sb.toString();
	}

}