public String invoke() throws Exception {

        String profileKey = "invoke: ";

        try {

            UtilTimerStack.push(profileKey);

            if (executed) {

                throw new IllegalStateException("Action has already executed");

            }

            //递归运行interceptor

            if (interceptors.hasNext())

{          //interceptors是InterceptorMapping实际上是像一个像//FilterChain一样的Interceptor链    

            //通过调用Invocation.invoke()实现递归牡循环 

                final InterceptorMapping interceptor = interceptors.next();

                String interceptorMsg = "interceptor: " + interceptor.getName();

                UtilTimerStack.push(interceptorMsg);

                try {

//在每一个Interceptor的方法中都会return invocation.invoke()                               

  resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);

                            }

                finally {

                    UtilTimerStack.pop(interceptorMsg);

                }

            } else {

//当全部interceptor都运行完,最后运行Action,invokeActionOnly会调用//invokeAction()方法

                resultCode = invokeActionOnly();

            }

  // this is needed because the result will be executed, then control will return to the Interceptor, which will

            // return above and flow through again

   //在Result返回之前调用preResultListeners     

        //通过executed控制,仅仅运行一次 

            if (!executed) {

                if (preResultListeners != null) {

                    for (Object preResultListener : preResultListeners) {

                        PreResultListener listener = (PreResultListener) preResultListener;

                        String _profileKey = "preResultListener: ";

                        try {

                            UtilTimerStack.push(_profileKey);

                            listener.beforeResult(this, resultCode);

                        }

                        finally {

                            UtilTimerStack.pop(_profileKey);

                        }

                    }

                }

                // now execute the result, if we‘re supposed to

//运行result。

                if (proxy.getExecuteResult()) {

                    executeResult();

                }

                executed = true;

            }

            return resultCode;

        }

        finally {

            UtilTimerStack.pop(profileKey);

        }

    }