How do I work with chained Hashmap in Java?

Question

I’m trying to popular a DTO through a received Json, in case I’m the Gson library, but I’m having trouble filling the field urlPhoto of my class hotelDTO. I can even convert Json to a Hoteldto object, but urlPhoto is null.

Json received:

{
      "location_id": "306267",
      "name": "EZ Aclimacao Hotel",
      "latitude": "-23.5771",
      "longitude": "-46.636818",
      "num_reviews": "900",
      "timezone": "America/Sao_Paulo",
      "location_string": "Sao Paulo, State of Sao Paulo",
      "photo": {
        "images": {
          "small": {
            "width": "150",
            "url": "https://media-cdn.tripadvisor.com/media/photo-l/19/62/7d/2d/fachada-do-ez.jpg",
            "height": "150"
          },
          "thumbnail": {
            "width": "50",
            "url": "https://media-cdn.tripadvisor.com/media/photo-t/19/62/7d/2d/fachada-do-ez.jpg",
            "height": "50"
          },
          "original": {
            "width": "2900",
            "url": "https://media-cdn.tripadvisor.com/media/photo-o/19/62/7d/2d/fachada-do-ez.jpg",
            "height": "1933"
          },
          "large": {
            "width": "550",
            "url": "https://media-cdn.tripadvisor.com/media/photo-s/19/62/7d/2d/fachada-do-ez.jpg",
            "height": "367"
          },
          "medium": {
            "width": "250",
            "url": "https://media-cdn.tripadvisor.com/media/photo-f/19/62/7d/2d/fachada-do-ez.jpg",
            "height": "167"
          }
        }
}

In this case I would like to take the value "url": "https://media-cdn.tripadvisor.com/media/photo-o/19/62/7d/2d/fachada-do-ez.jpg", which is in the following path, "photo" -> "images" -> "origianl" -> "url"

My Class DTO:

public class HotelDTO {

    @SerializedName("location_id")
    private String locantionId;
    @SerializedName("name")
    private String hotelName;
    @SerializedName("num_reviews")
    private int numReview;
    @SerializedName("location_string")
    private String location;
    @SerializedName("url")
    private Map<String, Map<String, Map<String, String>>> urlPhoto = new HashMap<String, Map<String, Map<String, String>>>();

    @Override
    public String toString() {
        return "HotelDTO{" +
                "locantionId='" + locantionId + '\'' +
                ", hotelName='" + hotelName + '\'' +
                ", numReview=" + numReview +
                ", location='" + location + '\'' +
                ", urlPhoto=" + urlPhoto +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        HotelDTO hotelDTO = (HotelDTO) o;
        return numReview == hotelDTO.numReview &&
                Objects.equals(locantionId, hotelDTO.locantionId) &&
                Objects.equals(hotelName, hotelDTO.hotelName) &&
                Objects.equals(location, hotelDTO.location) &&
                Objects.equals(urlPhoto, hotelDTO.urlPhoto);
    }

    @Override
    public int hashCode() {
        return Objects.hash(locantionId, hotelName, numReview, location, urlPhoto);
    }

    public String getLocantionId() {
        return locantionId;
    }

    public void setLocantionId(String locantionId) {
        this.locantionId = locantionId;
    }

    public String getHotelName() {
        return hotelName;
    }

    public void setHotelName(String hotelName) {
        this.hotelName = hotelName;
    }

    public int getNumReview() {
        return numReview;
    }

    public void setNumReview(int numReview) {
        this.numReview = numReview;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }

    public Map<String, Map<String, Map<String, String>>> getUrlPhoto() {
        return urlPhoto;
    }

    public void setUrlPhoto(Map<String, Map<String, Map<String, String>>> urlPhoto) {
        this.urlPhoto = urlPhoto;
    }
}

My Controller:

@Api(tags = "HotelEndpointTest")
@RestController
@RequestMapping("/api/hotelstest")
public class HotelsControllerTest {

    @RequestMapping(
            method = RequestMethod.GET,
            produces = {"application/json", "application/xml", "application/x-yaml"})
    public ResponseEntity<String> sendHotels(@RequestParam(value = "location_id", defaultValue = "303631") String locationId,
                                                           @RequestParam(value = "adults", defaultValue = "1") String adults,
                                                           @RequestParam(value = "checkin", defaultValue = "2020-08-10") String checkin,
                                                           @RequestParam(value = "rooms", defaultValue = "1") String rooms,
                                                           @RequestParam(value = "nights", defaultValue = "2") String nights,
                                                           @RequestParam(value = "zff", defaultValue = "") String zff,
                                                           @RequestParam(value = "pricesmin", defaultValue = "") String pricesmin,
                                                           @RequestParam(value = "offset", defaultValue = "") String offset,
                                                           @RequestParam(value = "subcategory", defaultValue = "") String subcategory,
                                                           @RequestParam(value = "pricesmax", defaultValue = "") String pricesmax,
                                                           @RequestParam(value = "hotel_class", defaultValue = "") String hotel_class,
                                                           @RequestParam(value = "currency", defaultValue = "BRL") String currency,
                                                           @RequestParam(value = "amenities", defaultValue = "") String amenities,
                                                           @RequestParam(value = "child_rm_ages", defaultValue = "") String child_rm_ages,
                                                           @RequestParam(value = "limit", defaultValue = "") String limit,
                                                           @RequestParam(value = "order", defaultValue = "") String order,
                                                           @RequestParam(value = "lang", defaultValue = "pt_BR") String lang,
                                                           @RequestParam(value = "sort", defaultValue = "recommended") String sort) {

        final RestTemplate restTemplate = new RestTemplate();
        final String url = "https://tripadvisor1.p.rapidapi.com/hotels/list?zff=" + zff + "&pricesmin=" + pricesmin + "&offset=" + offset +
                "&subcategory=" + subcategory + "&pricesmax=" + pricesmax + "&hotel_class=" + hotel_class + "&currency=" + hotel_class + "&amenities=" + amenities + "+&child_rm_ages=" + child_rm_ages + "&" +
                "limit=" + limit + "&order=" + order + "&lang=+" + lang + "&sort=" + sort + "&location_id=" + locationId + "&adults=" + adults + "&checkin=+" + checkin + "&rooms=" + rooms + "&nights=" + rooms;

        final HttpHeaders headers = new HttpHeaders();

        headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
        headers.setContentType(MediaType.APPLICATION_JSON);
        headers.set("x-rapidapi-host", "tripadvisor1.p.rapidapi.com");
        headers.set("x-rapidapi-key", "MEU_TOKEN");


        final HttpEntity httpEntity = new HttpEntity(headers);

        final ResponseEntity<String> responseEntity = restTemplate.exchange(
                url,
                HttpMethod.GET,
                httpEntity,
                String.class
        );


        JsonReader jsonReader = Json.createReader(new StringReader(responseEntity.getBody()));
        JsonObject jsonObject = jsonReader.readObject();
        Gson gson = new Gson();
        JsonArray jsonArray = jsonObject.get("data").asJsonArray();;


        List<HotelDTO> hotelDTO = new ArrayList<>();

        for (int i = 0; i < jsonArray.size() ; i++) {
            jsonObject = jsonArray.getJsonObject(i);
            hotelDTO.add(gson.fromJson(jsonObject.toString(), HotelDTO.class));
        }

        System.out.println(hotelDTO.size());


        return responseEntity;
    }

}

Answer 1

The problem is that the url is not found in the parent node. The URL is inside the Node photo.images.small or in photo.images.thumbnail or photo.images.original, etc..

Take a look at this solution: https://stackoverflow.com/questions/56614221/how-can-i-serialize-a-nested-object-using-gson-serializedname-in-java