对HandlerExecutionChain类的实例讲解

讲解HandlerExecutionChain之前，先大致了解下SpringMVC的核心开发步骤：

在web.xml中部署DispaterServlet，并配置springmvc.xml等文件;

将映射文件请求到处理器HandlerMapping;

HandlerMapping会把请求映射为HandlerExecutionChain类型的handler对象;

将handler对象作为参数传递给HandlerAdapter的实例化对象，调用其handler方法会生成一个ModelAndView对象;

通过ViewResolver视图解析器，将上一步骤中生成的ModelAndView解析为View;

DispatcherServlet根据获取到View，将视图返回给用户。

HandlerExecutionChain类比较简单，好理解。

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  HandlerExecutionChain {

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下面是类的部分属性。

  List<HandlerInterceptor>

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 applyPreHandle(HttpServletRequest request, HttpServletResponse response) = (! ( i = 0; i < interceptors.length; i++= (!interceptor.preHandle(request, response,  .interceptorIndex =

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 applyPostHandle(HttpServletRequest request, HttpServletResponse response, ModelAndView mv) = (! ( i = interceptors.length - 1; i >= 0; i--=

    /** * 这个方法只会执行preHandle()方法已经成功执行并且返回true的拦截器中的postHandle()方法。     */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);
                }
            }
        }
    }

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