spring攔截器實現seesion過時跳轉首頁

package com.zpedku.interceptor;

import com.zpedku.config.AppConfig;
import com.zpedku.model.SysUser;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang.StringUtils;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

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

/**
 * session過時跳轉頁面攔截器
 */
@Slf4j
public class SystemSessionInterceptor implements HandlerInterceptor {

    @Value("${projectName}")
    private String projectName;

    @Override
    public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object o) throws Exception {

        HttpSession session = req.getSession(true);
        String requestURI = req.getRequestURI();
        log.info("requestURI={}",requestURI);
        if(StringUtils.contains(requestURI, AppConfig.LOGIN_PATH)) return true;

        SysUser sysUser = (SysUser) session.getAttribute(AppConfig.SYS_USER_SESSION);
        if(sysUser!=null) return true;
        if(isAjax(req)){//如果ajax請求,直接設置請求頭session過時
            res.setHeader("sessionstatus", "timeout");
            res.sendError(518, "session timeout.");
        }else{
            //res.sendRedirect(req.getSession().getServletContext().getContextPath() + 
            //"/login.html");
            res.setContentType("text/html");
            res.setCharacterEncoding("utf-8");
            PrintWriter out = res.getWriter();
            StringBuilder builder = new StringBuilder();
            builder.append("<script type=\"text/javascript\" charset=\"UTF-8\">");
            //builder.append("alert(\"登陸已過時，請從新登陸！\");");
            builder.append("parent.window.location.href='"+req.getContextPath()+"/login.html';");
            builder.append("</script>");
            out.print(builder.toString());
            out.close();
            return false;

        }


        return false;
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {

    }

    /**
     * 判斷是不是ajax請求
     * @param req
     * @return
     */
    private boolean isAjax(HttpServletRequest req){
        if( req.getHeader("x-requested-with") != null && req.getHeader("x-requested-with").equals("XMLHttpRequest")) return true;
        return false;
    }

}