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);

}

}