ajax Session失效如何跳转到登录页面

在Struts应用中，我们发出的请求都会经过 相应的拦截器进行相关处理，一般都会有一个用户登录拦截（Session失效拦截）；一般请求的话，如果Session失效时，我们会跳到登录页面，可是如果我们采用AJAX请求时，将会返回登录页面的HTML代码，这肯定不是我们想要的，那么我们如何解决呢？请看以下步骤：

一、建立拦截器

package com.xxx.planeap.interceptor;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;
import org.apache.struts2.ServletActionContext;

import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.ActionSupport;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;
import com.xxx.common.contants.ConstantsKey;
import com.xxx.common.contants.SessionKey;
import com.xxx.planeap.domain.User;
import com.xxx.planeap.security.SecurityContextUtil;

/**
 * 
 * @author Goma OMA1989@YEAH.NET
 * @version v1.0
 * @since 2012-05-31
 
 * 
 */
public class SecurityInterceptor extends AbstractInterceptor {
    private static final long serialVersionUID = 1L;
    private Logger logger = Logger.getLogger(SecurityInterceptor.class);

    @Override
    public String intercept(ActionInvocation invocation) throws Exception {
        // TODO Auto-generated method stub

        String className = invocation.getAction().getClass().getName();
        String action = className.substring(className.lastIndexOf(".")+1,className.length());
        String actionName = invocation.getProxy().getActionName();
        
        String result;
        HttpServletRequest request = ServletActionContext.getRequest();
        HttpServletResponse response = ServletActionContext.getResponse();
        String type = request.getHeader("X-Requested-With");
        User user = (User) ActionContext.getContext().getSession().get(SessionKey.CURRENT_USER);
        if (user == null) {
            logger.debug("SECURITY CHECKED: NEED TO LOGIN");
            if ("XMLHttpRequest".equalsIgnoreCase(type)) {// AJAX REQUEST PROCESS
                response.setHeader("sessionstatus", ConstantsKey.MSG_TIME_OUT);
                result = null;
            } else {// NORMAL REQUEST PROCESS
                result = ActionSupport.LOGIN;
            }
        } else {
            logger.debug("SECURITY CHECKED: USER HAS LOGINED");
            SecurityContextUtil.setCurrentUser(user);
            boolean hanPerm = SecurityContextUtil.hasPerm(action, actionName);
            logger.debug("SECURITY CHECKED: PERMISSION---"+action+"."+actionName+"="+hanPerm);
            result = invocation.invoke();
        }
        return result;
    }
}

二、定义全局AJAX请求结束处理方法

//全局的AJAX访问，处理AJAX清求时SESSION超时
$.ajaxSetup({
    contentType:"application/x-www-form-urlencoded;charset=utf-8",
    complete:function(XMLHttpRequest,textStatus){
          //通过XMLHttpRequest取得响应头，sessionstatus           
          var sessionstatus=XMLHttpRequest.getResponseHeader("sessionstatus"); 
          if(sessionstatus=="timeout"){
               //这里怎么处理在你，这里跳转的登录页面
               window.location.replace(PlanEap.getActionURI("login"));
       }
    }
});