在上一篇部落格springMVC原始碼分析--HandlerInterceptor攔截器（一）中我們介紹了HandlerInterceptor攔截器相關的內容，瞭解到了HandlerInterceptor提供的三個介面方法：

（1）preHandle: 在執行controller處理之前執行，返回值為boolean ,返回值為true時接著執行postHandle和afterCompletion，如果我們返回false則中斷執行
（2）postHandle:在執行controller的處理後，在ModelAndView處理前執行
（3）afterCompletion ：在DispatchServlet執行完ModelAndView之後執行

我們可以看到這三個方法的呼叫過程是不一樣的，接下來我們分析一下這個三個方法具體呼叫實現的地方。其最終實現呼叫的地方是在doDispatch函式中，因為doDispatch完成了一個請求到返回資料的完整操作。

protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {

		HandlerExecutionChain mappedHandler = null;
		
		.......

		try {
			ModelAndView mv = null;
			Exception dispatchException = null;

			try {
				
				.......
				//獲取HandlerExecutionChain
				mappedHandler = getHandler(processedRequest);
				
				......
				//最終會呼叫HandlerInterceptor的preHandle方法
				if (!mappedHandler.applyPreHandle(processedRequest, response)) {
					return;
				}
// 
 
呼叫具體的Controller中的處理方法Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
				......
				//最終會呼叫HandlerInterceptor的postHandle方法
				mappedHandler.applyPostHandle(processedRequest, response, mv);
			}
			catch (Exception ex) {
				dispatchException = ex;
			}
			processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
		}
		catch (Exception ex) {
			//最終會呼叫HandlerInterceptor的afterCompletion 方法
			triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
		}
		catch (Error err) {
			//最終會呼叫HandlerInterceptor的afterCompletion 方法
			triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err);
		}
		finally {
			if (asyncManager.isConcurrentHandlingStarted()) {
				// Instead of postHandle and afterCompletion
				if (mappedHandler != null) {
					mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
				}
			}
			else {
				// Clean up any resources used by a multipart request.
				if (multipartRequestParsed) {
					cleanupMultipart(processedRequest);
				}
			}
		}
	}
 

mappedHandler.applyPreHandle(processedRequest, response)：最終會呼叫HandlerInterceptor的preHandle方法。在HandlerExecutionChain中的具體實現如下，我們可以看到會呼叫所有的HandlerInterceptor攔截器並呼叫其preHandler方法。

boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HandlerInterceptor[] interceptors = getInterceptors();//獲取所有的攔截器
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = 0; i < interceptors.length; i++) {
				HandlerInterceptor interceptor = interceptors[i];
				if (!interceptor.preHandle(request, response, this.handler)) {//分別呼叫攔截器的preHandle方法
					triggerAfterCompletion(request, response, null);
					return false;
				}
				this.interceptorIndex = i;
			}
		}
		return true;
	}

mappedHandler.applyPostHandle(processedRequest, response, mv)：最終會呼叫HandlerInterceptor的postHandle方法

具體實現是在HandlerExecutionChain中實現如下，就是獲取所有的攔截器並呼叫其postHandle方法。

void applyPostHandle(HttpServletRequest request, HttpServletResponse response, ModelAndView mv) throws Exception {
		HandlerInterceptor[] interceptors = getInterceptors();//獲取所有攔截器
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = interceptors.length - 1; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				interceptor.postHandle(request, response, this.handler, mv);//分別呼叫攔截器的postHandle方法
			}
		}
	}

triggerAfterCompletion(processedRequest, response, mappedHandler, ex)：最終會呼叫HandlerInterceptor的afterCompletion 方法
triggerAfterCompletionWithError(processedRequest, response, mappedHandler, err)：最終會呼叫HandlerInterceptor的afterCompletion 方法

private void triggerAfterCompletionWithError(HttpServletRequest request, HttpServletResponse response,
			HandlerExecutionChain mappedHandler, Error error) throws Exception {

		ServletException ex = new NestedServletException("Handler processing failed", error);
		if (mappedHandler != null) {
			mappedHandler.triggerAfterCompletion(request, response, ex);
		}
		throw ex;
	}

private void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response,
			HandlerExecutionChain mappedHandler, Exception ex) throws Exception {

		if (mappedHandler != null) {
			mappedHandler.triggerAfterCompletion(request, response, ex);
		}
		throw ex;
	}

void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, Exception ex)
			throws Exception {

		HandlerInterceptor[] interceptors = getInterceptors();//獲取所有攔截器
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = this.interceptorIndex; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				try {
					interceptor.afterCompletion(request, response, this.handler, ex);//呼叫攔截器的afterCompletion方法
				}
				catch (Throwable ex2) {
					logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
				}
			}
		}
	}

通過以上程式碼分析我們可以看到HandlerInterceptor攔截器的最終呼叫實現是在DispatcherServlet的doDispatch方法中，並且SpringMVC提供了HandlerExecutionChain來幫助我們執行所有配置的HandlerInterceptor攔截器，並分別呼叫HandlerInterceptor所提供的方法。