code: @JSONField(serialize = false)
      public String[] getXhashNames() {
          List<Obj> xhash = getXhash();
          String[] xhashNames = new String[xhash.size()];
          for (int i = 0; i < xhash.size(); i++) {
              xhashNames[i] = xhash.get(i).getName();
          }
          return xhashNames;
      }
docs: xhash属性名视图，如果不存在xhash属性，那么返回空数组，而不是null