/**
  * 构建 查询条件
  *
  * @param clazz
  * @return
  */
 public DetachedCriteria toCriteria(Class<?> clazz) {
   DetachedCriteria criteria = DetachedCriteria.forClass(clazz, "entity");
   for (WhereCondition con : cons) {
     criteria.add(con.getCriterion());
   }
   return criteria;
 }
  /** 构建查询条件 where 语句 如 “ and xx=yy and ....”: */
  public String appendedStr() {
    String where = "";

    for (WhereCondition condition : cons) where += " and " + condition.toString();
    return where;
  }