code: public OrderBy orderBy(String name, String dir) {
          if ("asc".equalsIgnoreCase(dir)) {
              this.asc(name);
          } else {
              this.desc(name);
          }
          return this;
      }
docs: 当dir为asc时判断为升序,否则判定为降序. cnd.orderBy("age", "asc")
  @param name Java属性/字段属性
  @param dir asc或其他
  @return OrderBy实例,事实上就是当前对象