Struts2拦截器 —— prepare拦截器

实现类
com.opensymphony.xwork2.interceptor.PrepareInterceptor
 
作用
为实现了com.opensymphony.xwork2.Preparable接口的action调用相关方法。
 
两个参数

参数名	值类型	默认值	描述
alwaysInvokePrepare	boolean	true	如果其值为true则调用接口定义的prepare方法。
firstCallPrepareDo	boolean	false	如果值为true，则调用prepareDoXXX方法。 否则调用prepareXXX方法(XXX为action对应的方法)。

 
关键源码

public String doIntercept(ActionInvocation invocation) throws Exception {         Object action = invocation.getAction();         if (action instanceof Preparable) {             try {                 String[] prefixes;                 if (firstCallPrepareDo) {                     prefixes = new String[] {ALT_PREPARE_PREFIX, PREPARE_PREFIX};                 } else {                     prefixes = new String[] {PREPARE_PREFIX, ALT_PREPARE_PREFIX};                 }                 PrefixMethodInvocationUtil.invokePrefixMethod(invocation, prefixes);             }             catch (InvocationTargetException e) {                 /*                  * The invoked method threw an exception and reflection wrapped it                  * in an InvocationTargetException.                  * If possible re-throw the original exception so that normal                  * exception handling will take place.                  */                 Throwable cause = e.getCause();                 if (cause instanceof Exception) {                     throw (Exception) cause;                 } else if(cause instanceof Error) {                     throw (Error) cause;                 } else {                     /*                      * The cause is not an Exception or Error (must be Throwable) so                      * just re-throw the wrapped exception.                      */                     throw e;                 }             }             if (alwaysInvokePrepare) {                 ((Preparable) action).prepare();             }         }         return invocation.invoke();     }

 
执行顺序
在struts2中,如果Action实现了Prepare接口：
prepare<方法名>()
 --> prepare() --> validate<方法名>方法
--> execute方法