// 对象转字符串
String string = JSONObject.toJSONString(moveDto);
Gson gson = new Gson();
// 集合转字符串
String s = gson.toJson(moveDto.getActivity().getRuler());
// 字符串转回集合
List<MoveDto.Activity.Rule> rule3 = gson.fromJson(s, new TypeToken<List<MoveDto.Activity.Rule>>() {
}.getType());