拦截器(Interceptor)中的invocation.invoke()

  1 关于在Struts2的自定义的验证拦截器（Interceptor）中的invocation.invoke()是什么意思？
  2 
  3  
  4 
  5  
  6 package com.xjtu.interceptor;  
  7   
  8 import com.opensymphony.xwork2.ActionContext;  
  9 import com.opensymphony.xwork2.ActionInvocation;  
 10 import com.opensymphony.xwork2.interceptor.Interceptor;  
 11   
 12 public class PermissionInterceptor implements Interceptor {  
 13   
 14     /** 
 15      *  
 16      */  
 17     private static final long serialVersionUID = 1L;  
 18   
 19     @Override  
 20     public void destroy() {  
 21         // TODO Auto-generated method stub  
 22   
 23     }  
 24   
 25     @Override  
 26     public void init() {  
 27         // TODO Auto-generated method stub  
 28   
 29     }  
 30   
 31     @Override  
 32     public String intercept(ActionInvocation invocation) throws Exception {  
 33         System.out.println("进入拦截器");  
 34         Object user = ActionContext.getContext().getSession().get("user");  
 35         System.out.println(user);  
 36         if (user != null) {  
 37             return invocation.invoke();  
 38         }  
 39         ActionContext.getContext().put("message", "您无权执行该操作！");  
 40         return "success";  
 41     }  
 42   
 43 }  
 44 
 45 
 46 
 47  
 48 
 49  
 50 package com.xjtu.soft;  
 51   
 52 public class HelloWorldAction {  
 53     private String message;  
 54   
 55     public String getMessage() {  
 56         return message;  
 57     }  
 58       
 59     public void setMessage(String message) {  
 60         this.message = message;  
 61     }  
 62       
 63     public String execute(){  
 64         System.out.println("执行execute");  
 65         message = "execute";  
 66         return "success";  
 67     }  
 68   
 69     public String addUI() {  
 70         System.out.println("执行addUI");  
 71         message = "addUI";  
 72         return "success";  
 73     }  
 74   
 75   
 76 }  
 77 
 78 
 79 
 80 struts.xml配置自定义的拦截器如下：
 81 
 82  
 83 
 84  
 85 <?xml version="1.0" encoding="UTF-8" ?>  
 86 <!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">  
 87 <struts>  
 88     <constant name="struts.action.extension" value="do,action" />  
 89     <constant name="struts.multipart.maxSize" value="10485760" />  
 90   
 91   
 92     <package name="itcast" namespace="/test" extends="struts-default">  
 93         <interceptors>  
 94             <interceptor name="permission"  
 95                 class="com.xjtu.interceptor.PermissionInterceptor" />  
 96             <interceptor-stack name="permissionstack">  
 97                 <interceptor-ref name="defaultStack"></interceptor-ref>  
 98                 <interceptor-ref name="permission"></interceptor-ref>  
 99             </interceptor-stack>  
100         </interceptors>  
101           
102         <global-results>  
103             <result name="success">/WEB-INF/page/message.jsp</result>  
104         </global-results>  
105   
106         <action name="list_*" class="com.xjtu.soft.HelloWorldAction"  
107             method="{1}">  
108             <interceptor-ref name="permissionstack"></interceptor-ref>  
109         </action>  
110     </package>  
111   
112 </struts>      
113 
114 
115 
116 
117 invocation.invoke() 就是通知struts2接着干下面的事情
118 比如 调用下一个拦截器 或 执行下一个Action
119 就等于退出了你自己编写的这个interceptor了
120  
121 
122 如何使用struts2拦截器，或者自定义拦截器。特别注意，在使用拦截器的时候，在Action里面必须最后一定要引用struts2自带的拦截器缺省堆栈defaultStack,如下(这里我是引用了struts2自带的checkbox拦截器)：
123 
124 <interceptor-ref name="checkbox">
125   <param name="uncheckedValue">0</param>
126 </interceptor-ref>
127 <interceptor-ref name="defaultStack"/>
128 ******(必须加，否则出错)