Convert java data object to service object

List<VehicleDO> realList = Arrays.asList(list);

List<BuyingDO> realList = new ArrayList<BuyingDO>(list.length);
for (VehicleDO vdo : list){
    realList.add((BuyingDO)vdo);
}

class JsonRequest<T>{
  private String request;
    private T data;

    public String getRequest() {
        return request;
    }

    public void setRequest(String request) {
        this.request = request;
    }

    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }
}

class UserInfoRequest extends JsonRequest<UserInfo>{
//nothing in here
}

String output = getCategoryServiceController.myGetCategory();

public <T> T readValue(String content,
          Class<T> valueType)
        throws IOException,
               JsonParseException,
               JsonMappingException

String output = getCategoryServiceController.myGetCategory();
LOGGER.debug("output {} ", output

GetCategoryResponseDto dto = mapper.readValue(json, GetCategoryResponseDto.class

return Optional.of(dto);

Optional<GetCategoryResponseDto> optional;
org.json.simple.JSONObject json = null;