深入struts2.0--ActionInvocation接口以及3DefaultActionInvocation类

Posted 2020-09-17 mthoutai

1.1.1       ActionInvocation类

ActionInvocation定义为一个接口。主要作用是表现action的运行状态。它拥有拦截器和action的实例。通过重复的运行invoke方法。首先被actionProxy,然后是拦截器，全部拦截器运行完后就是action和result .

图3.3.4 ActionInvocation类的主要方法

1.1.2       DefaultActionInvocation类

DefaultActionInvocation类是ActionInvocation接口的实现类. 一般都用该类实例化ActionInvocation。 基本的方法例如以下：

 

图3.3.5 DefaultActionInvocation类的主要方法

关键方法：invoke（）方法

executed = false; 默觉得false。表示该action还没有运行。

假设运行就会抛出已经运行的异常。

然后推断拦截器是否已经配置，假设配置了拦截器就会从配置信息中获得拦截器配置类InterceptorMapping。

此类中仅仅包括两个属性，一个就是name和interceptor实例。

 

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);         }     }