import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class LoginInterceptor extends AbstractInterceptor {

    public String intercept (ActionInvocation invocation) throws Exception {
        String statte = (String) ServletActionContext.getRequest().getSession().getAttribute ("login_state"); //获取登陆状态
        if (statte != null) {  //判断是否为空
            return invocation.invoke();  //如果为是，继续执行ACTION方法
        } else {
            return "backerror";   //如果为否，弹出
        }
    }
}




<interceptors> 
           <interceptor name="authority" class="org.yzsoft.examdemo.action.LoginInterceptor"></interceptor> 
        <!-- 拦截器栈 -->     
           <interceptor-stack name="myDefault"> 
               <interceptor-ref name="defaultStack"></interceptor-ref> 
               <interceptor-ref name="authority"></interceptor-ref> 
           </interceptor-stack> 
          
       </interceptors> 
 
       <global-results> 
    <!-- 当返回error视图名时，转入/error.jsp页面 -->     
           <result name="backerror">error.jsp</result> 
           <result name="fronterror">login.jsp</result> 
       </global-results>