Example explanation of HandlerExecutionChain class

Before explaining HandlerExecutionChain, let’s have a general understanding of the core development steps of SpringMVC:

Deploy DispaterServlet in web.xml, and configure springmvc.xml and other files;

Request the mapping file to Processor HandlerMapping;

HandlerMapping will map the request to a handler object of type HandlerExecutionChain;

Pass the handler object as a parameter to the instantiation object of HandlerAdapter, and calling its handler method will generate a ModelAndView object ;

Use the ViewResolver view parser to parse the ModelAndView generated in the previous step into a View;

DispatcherServlet returns the view to the user based on the obtained View.

The HandlerExecutionChain class is relatively simple and easy to understand.

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  HandlerExecutionChain {

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The following are some attributes of the class.

  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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