拦截器(Interceptor)中的invocation.invoke()

关于在Struts2的自定义的验证拦截器（Interceptor）中的invocation.invoke()是什么意思？

 

 
package com.xjtu.interceptor;  
  
import com.opensymphony.xwork2.ActionContext;  
import com.opensymphony.xwork2.ActionInvocation;  
import com.opensymphony.xwork2.interceptor.Interceptor;  
  
public class PermissionInterceptor implements Interceptor {  
  
    /** 
     *  
     */  
    private static final long serialVersionUID = 1L;  
  
    @Override  
    public void destroy() {  
        // TODO Auto-generated method stub  
  
    }  
  
    @Override  
    public void init() {  
        // TODO Auto-generated method stub  
  
    }  
  
    @Override  
    public String intercept(ActionInvocation invocation) throws Exception {  
        System.out.println("进入拦截器");  
        Object user = ActionContext.getContext().getSession().get("user");  
        System.out.println(user);  
        if (user != null) {  
            return invocation.invoke();  
        }  
        ActionContext.getContext().put("message", "您无权执行该操作！");  
        return "success";  
    }  
  
}  



 

 
package com.xjtu.soft;  
  
public class HelloWorldAction {  
    private String message;  
  
    public String getMessage() {  
        return message;  
    }  
      
    public void setMessage(String message) {  
        this.message = message;  
    }  
      
    public String execute(){  
        System.out.println("执行execute");  
        message = "execute";  
        return "success";  
    }  
  
    public String addUI() {  
        System.out.println("执行addUI");  
        message = "addUI";  
        return "success";  
    }  
  
  
}  



struts.xml配置自定义的拦截器如下：

 

 
<?xml version="1.0" encoding="UTF-8" ?>  
<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.1//EN" "http://struts.apache.org/dtds/struts-2.1.dtd">  
<struts>  
    <constant name="struts.action.extension" value="do,action" />  
    <constant name="struts.multipart.maxSize" value="10485760" />  
  
  
    <package name="itcast" namespace="/test" extends="struts-default">  
        <interceptors>  
            <interceptor name="permission"  
                class="com.xjtu.interceptor.PermissionInterceptor" />  
            <interceptor-stack name="permissionstack">  
                <interceptor-ref name="defaultStack"></interceptor-ref>  
                <interceptor-ref name="permission"></interceptor-ref>  
            </interceptor-stack>  
        </interceptors>  
          
        <global-results>  
            <result name="success">/WEB-INF/page/message.jsp</result>  
        </global-results>  
  
        <action name="list_*" class="com.xjtu.soft.HelloWorldAction"  
            method="{1}">  
            <interceptor-ref name="permissionstack"></interceptor-ref>  
        </action>  
    </package>  
  
</struts>      




invocation.invoke() 就是通知struts2接着干下面的事情
比如 调用下一个拦截器 或 执行下一个Action
就等于退出了你自己编写的这个interceptor了
 

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)：

<interceptor-ref name="checkbox">
  <param name="uncheckedValue">0</param>
</interceptor-ref>
<interceptor-ref name="defaultStack"/>
******(必须加，否则出错)