DetachedCriteria和Criteria的使用方法

/*
* 下载统计
* @return
*/
public String downloadStatistics(){
  logger.info("正在执行目录内容统计下载");

  String type = getServletRequest().getParameter("type");
  DetachedCriteria dc = DetachedCriteria.forClass(TbXymlb.class)
    .add(Restrictions.and(Restrictions.isNotNull("sfsjtc"), Restrictions.isNotNull("mlnrb")))
    .addOrder(Order.asc("diyu")).addOrder(Order.asc("cydw"));

  logger.info("执行查询参数为:{}", type);
  if(DOWNLOAD_TYPE_ZY.equals(type)){
   dc.add(Restrictions.eq("diyu", "99"));
  }else if(DOWNLOAD_TYPE_DF.equals(type)){
   dc.add(Restrictions.ne("diyu", "99"));
  }

  // 执行查询
  List<TbXymlb> xymls = xymlService.query(dc);

  try{

   downloadName = "mlnr_tj.xls";
   downloadFile = buildXLSStream(xymls);

  }catch(Exception error){
   logger.error("下载出现错误", error);
  }

  return SUCCESS;
}

随后要加上自己的理解