String requestType = request.getHeader("X-Requested-With");
if(requestType != null && "XMLHttpRequest".equalsIgnoreCase(requestType.trim())) {
  //如果是ajax请求
  response.setHeader("sessionStatus", "timeout");
  response.sendError(601, "session timeout.");
  return false;
}

//设置Ajax请求的全局默认options
jQuery.ajaxSetup({
  type:'post',
  complete:function(xhr, ts){ //XMLHttpRequest, textStatus
    var sessionStatus = xhr.getResponseHeader('sessionstatus');
    if(sessionStatus == 'timeout') {
      alert('页面过期，请重新登录!');
      window.top.location.href = 'Login.htm';
    }
  }
});

$('#example').dataTable( {
 "ajax": {
  "url": "findRoles.htm",
  "type": "POST",
  "error": function(xhr, ts, et) { //XMLHttpRequest, textStatus, errorThrown
    var sessionStatus = xhr.getResponseHeader('sessionstatus');
    if(sessionStatus == 'timeout') {
      alert('页面过期，请重新登录!');
      window.top.location.href = 'Login.htm';
    }
  }
 }
});