Dabbaghi.com

@Component
public class WeatherApiAdapter {
    private final RestClient restClient;
    public WeatherInfo fetch(String city) {
        ExternalWeatherDto dto = restClient.get()
                .uri("/weather?city={c}", city)
                .retrieve()
                .body(ExternalWeatherDto.class);
        return new WeatherInfo(dto.temp_c(), dto.condition().text());
    }
}

public interface CityRepository extends JpaRepository<City, Long> {
    Optional<City> findByName(String name);
}

@Service
public class WeatherService {
    private final WeatherApiAdapter adapter;
    private final CityRepository cityRepository;
    public String forecastFor(String cityName) {
        City city = cityRepository.findByName(cityName)
                .orElseThrow(() -> new CityNotFoundException(cityName));
        WeatherInfo info = adapter.fetch(city.getName());
        return info.temp() > 25 ? "Hot in " + cityName : "Mild in " + cityName;
    }
}

@Component
@Primary
public class CachingWeatherAdapter implements WeatherPort {
    private final WeatherApiAdapter delegate;
    private final Map<String, WeatherInfo> cache = new ConcurrentHashMap<>();
    public WeatherInfo fetch(String city) {
        return cache.computeIfAbsent(city, delegate::fetch);
    }
}

@Component
public class TripPlannerFacade {
    private final WeatherService weatherService;
    private final FlightService flightService;
    private final HotelService hotelService;
    public TripPlan planTrip(String city) {
        return new TripPlan(
                weatherService.forecastFor(city),
                flightService.findFlights(city),
                hotelService.findHotels(city));
    }
}