拦截器代码

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

import java.util.Map;

/**
 * Created by allme on 2016/5/25.
 */
public class LoginInterceptor extends AbstractInterceptor {

    @Override
    public String intercept(ActionInvocation actionInvocation) throws Exception {
        try{
            Map session = actionInvocation.getInvocationContext().getSession();
            String username = (String) session.get("username");
            String userpwd = (String) session.get("userpwd");
            if("".equals(username)||"".equals(userpwd)||username==null||userpwd==null){
                System.out.println("what "+username);
                System.out.println("what "+userpwd);
                return "login";
            }
            else{
                return actionInvocation.invoke();
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            return null;
        }
    }
}

配置文件

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE struts PUBLIC
        "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
        "http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>
    <package name="register" extends="struts-default">
        <action name="useraction" class="cn.edu.zucc.action.UserAction">
            <result name="showuser">/showuser.jsp</result>
        </action>
    </package>
    <package name="login" extends="struts-default">
        <interceptors>
            <interceptor name="Login" class="cn.edu.zucc.interceptot.LoginInterceptor" />
            <interceptor-stack name="loginstack">
                <interceptor-ref name="defaultStack"></interceptor-ref>
                <interceptor-ref name="Login"></interceptor-ref>
                <interceptor-ref name="timer"></interceptor-ref>
            </interceptor-stack>
        </interceptors>
        
        <global-results>
            <result name="login">/login.jsp</result>
        </global-results>
        <action name="Login" class="cn.edu.zucc.action.LoginAction">
            <result name="error">/error.jsp</result>
            <result name="admin">/admin.jsp</result>
            <result name="user">/user.jsp</result>
            <result name="login">/login.jsp</result>
        </action>
        <action name="Hello" class="cn.edu.zucc.action.HelloAction">
            <result name="showuser">/showuser.jsp</result>
            <result name="login">/login.jsp</result>
            <interceptor-ref name="loginstack"></interceptor-ref>
        </action>
    </package>
</struts>