SpringMVC拦截器实现监听session是否过期详解

<mvc:interceptors>  <mvc:interceptor>    <mvc:mapping path="/**"/>    <mvc:exclude-mapping path="/user/login"/>  <!-- 不拦截登录请求 -->    <mvc:exclude-mapping path="/user/logout"/>  <!-- 不拦截注销请求 -->    <mvc:exclude-mapping path="*.jsp"/>    <mvc:exclude-mapping path="*.html"/>    <mvc:exclude-mapping path="*.js"/>    <mvc:exclude-mapping path="*.css"/>    <bean class="org.huaxin.interceptor.AccessInterceptor"></bean>  </mvc:interceptor></mvc:interceptors>

public boolean preHandle(HttpServletRequest request, HttpServletResponse response,      Object obj) throws Exception {    System.out.println("[AccessInterceptor]:preHandle执行");    HttpSession session = request.getSession();    ServletContext application = session.getServletContext();    if(application.getAttribute(session.getId()) == null){  //未登录      PrintWriter out = response.getWriter();      StringBuffer sb = new StringBuffer("<script type=/"text/javascript/" charset=/"UTF-8/">");      sb.append("alert(/"你的账号被挤掉，或者没有登录，或者页面已经过期，请重新登录/")");      sb.append("window.location.href='/user/logout';");      sb.append("</script>");      out.print(sb.toString());      out.close();      return false;    }else{  //已经登录      return true;    }  }