JpaCityService.kt

@Service
@Transactional
internal class JpaCityService(val cityRepo: CityRepository) : CityService {

  override fun retrieveCity(cityId: Long) : CityDto? {
    return cityRepo.findOne(cityId)?.toDto()
  }

  override fun retrieveCities() : List<CityDto> {
    return cityRepo.findAll().map { it.toDto() }
  }

  override fun addCity(city: CreateCityDto) : CityRepo {
    return cityRepo.save(CityEntity.fromDto(city)).toDto()
  }

  override fun updateCity(id: Long, city: UpdateCityDto): CityDto? {
    val currentCity = cityRepo.findOne(id)
    return if (currentCity != null) cityRepo.save(CityEntity.fromDto(city, currentCity)).toDto()
    else null
  }
}