深入struts2.0(七)--ActionInvocation介面以及3DefaultActionInvocation類

標籤：struts   struts2.0   技術   

1.1.1       ActionInvocation類

ActionInvocation定義為一個介面，主要作用是表現action的執行狀態。它擁有攔截器和action的執行個體。通過反覆的執行invoke方法。首先被actionProxy,然後是攔截器，所有攔截器執行完後就是action和result .

圖3.3.4 ActionInvocation類的主要方法

1.1.2       DefaultActionInvocation類

DefaultActionInvocation類是ActionInvocation介面的實作類別. 一般都用該類執行個體化ActionInvocation。 主要的方法如下：

 

圖3.3.5 DefaultActionInvocation類的主要方法

關鍵方法：invoke（）方法

executed = false; 預設為false，表示該action還沒有執行。 如果執行就會拋出已經執行的異常。

然後判斷攔截器是否已經配置，如果配置了攔截器就會從配置資訊中獲得攔截器配置類InterceptorMapping。此類中只包含兩個屬性，一個就是name和interceptor執行個體。

 

public String invoke() throws Exception {         String profileKey = "invoke: ";         try {             UtilTimerStack.push(profileKey);             if (executed) {                 throw new IllegalStateException("Action has already executed");             }             //遞迴執行interceptor             if (interceptors.hasNext()) {          //interceptors是InterceptorMapping實際上是像一個像//FilterChain一樣的Interceptor鏈                 //通過調用Invocation.invoke()實現遞迴牡迴圈                  final InterceptorMapping interceptor =interceptors.next();                 String interceptorMsg = "interceptor: " + interceptor.getName();                 UtilTimerStack.push(interceptorMsg);                 try { //在每個Interceptor的方法中都會return invocation.invoke()                                  resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);                             }                 finally {                     UtilTimerStack.pop(interceptorMsg);                 }             } else { //當所有interceptor都執行完,最後執行Action,invokeActionOnly會調用//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返回之前調用preResultListeners              //通過executed控制,只執行一次              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 //執行result。                 if (proxy.getExecuteResult()) {                     executeResult();                 }                 executed = true;             }             return resultCode;         }         finally {             UtilTimerStack.pop(profileKey);         }     }