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

我就是我 2022-07-14 12:46 191阅读 0赞

上一篇博客[springMVC源码分析--HandlerInterceptor拦截器调用过程（二）][springMVC_--HandlerInterceptor]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();
    	}
    
    }

[springMVC_--HandlerInterceptor]: http://blog.csdn.net/qq924862077/article/details/53541678