SpringMVC 拦截器源码解析(3)

private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, HandlerExecutionChain mappedHandler, ModelAndView mv, Exception exception) throws Exception {
        boolean errorView = false;
        if(exception != null) {
            if(exception instanceof ModelAndViewDefiningException) {
                this.logger.debug("ModelAndViewDefiningException encountered", exception);
                mv = ((ModelAndViewDefiningException)exception).getModelAndView();
            } else {
                Object handler = mappedHandler != null?mappedHandler.getHandler():null;
                mv = this.processHandlerException(request, response, handler, exception);
                errorView = mv != null;
            }
        }

if(mv != null && !mv.wasCleared()) {
            this.render(mv, request, response);
            if(errorView) {
                WebUtils.clearErrorRequestAttributes(request);
            }
        } else if(this.logger.isDebugEnabled()) {
            this.logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + this.getServletName() + "': assuming HandlerAdapter completed request handling");
        }

if(!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
            if(mappedHandler != null) {
                mappedHandler.triggerAfterCompletion(request, response, (Exception)null);
            }

}
    }

　　从 doDispatch() 方法这里主要需要知道 HandlerExecutionChain mappedHandler = this.getHandler(processedRequest); 这一句调用的 getHandler() 方法，源码如下。

　　getHandle() 方法里是通过 HandlerMapping 的 getHandler 方法返回 HandlerExecutionChain 的。

　　从代码中不难看出整个逻辑就是依次判断 servlet 中的每个 handlerMapping 是否能够匹配该请求，直到找到那个匹配的然后返回处理结果。

protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
        Iterator var2 = this.handlerMappings.iterator();

HandlerExecutionChain handler;
        do {
            if(!var2.hasNext()) {
                return null;
            }

HandlerMapping hm = (HandlerMapping)var2.next();
            if(this.logger.isTraceEnabled()) {
                this.logger.trace("Testing handler map [" + hm + "] in DispatcherServlet with name '" + this.getServletName() + "'");
            }

handler = hm.getHandler(request);
        } while(handler == null);

return handler;
    }

HandlerExecutionChain 类

　　applyPreHandle() 方法源码如下：可以看出是顺序调用拦截器的 preHandle() 方法。preHandle 返回 false 时调用了 triggerAfterCompletion 方法。

boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
        HandlerInterceptor[] interceptors = this.getInterceptors();
        if(!ObjectUtils.isEmpty(interceptors)) {
            for(int i = 0; i < interceptors.length; this.interceptorIndex = i++) {
                HandlerInterceptor interceptor = interceptors[i];
                if(!interceptor.preHandle(request, response, this.handler)) {
                    this.triggerAfterCompletion(request, response, (Exception)null);
                    return false;
                }
            }
        }

return true;
    }

　　applyPostHandle() 方法源码如下：可以看出这里是逆序调用 postHandle 方法。