Android java: How to create POJO and convert it into acceptable JSON for Cloud Firestore REST API

I made preview test REST API query via postman like this

https://firestore.googleapis.com/v1/projects/MY_PROJECT_ID/databases/(default)/documents/USER_ID_HASH/documents/112233445566

JSON body example:

{
"fields": {
"longitude": {
"doubleValue": 35.5635
},
"latitude": {
"doubleValue": 45.5366
}
}
}

And getting http response 200, so going to implement this in code using retrofit2.

The issue is that "doubleValue" is something like field transformation according to value type, so it may be also "stringValue" or "integerValue" for example. And question is how to create POJO class for further converting in JSON body like JSON body example above?

What do I have for now:

API

public interface PlaceholderApi {

@POST("{userId}/documents/{timestamp}")
Call<Transaction.Result> saveLocationToCloud(
@Path("userId") String userId,
@Path("timestamp") long timestamp,
@Body LocationData data
);

}

Network service

public class NetworkService {
private static NetworkService instance;
private static final String WEB_API_KEY = "zaSy..........VWI";
private static final String BASE_URL_CLOUD
= "https://firestore.googleapis.com/v1/projects/alocationtracker/databases/(default)/documents/";
private Retrofit retrofit;
private NetworkService() {
HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
OkHttpClient.Builder client = new OkHttpClient.Builder()
.addInterceptor(interceptor);
client.interceptors().add(chain -> {
Request request = chain.request();
HttpUrl url = request.url().newBuilder().addQueryParameter("key", WEB_API_KEY).build();
request = request.newBuilder().url(url).build();
return chain.proceed(request);
});
retrofit = new Retrofit.Builder()
.baseUrl(BASE_URL_CLOUD)
.addConverterFactory(GsonConverterFactory.create())
.client(client.build())
.build();
}
public static NetworkService getInstance() {
if (instance == null) {
instance = new NetworkService();
}
return instance;
}
public PlaceholderApi getJsonApi() {
return retrofit.create(PlaceholderApi.class);
}

}

POJO

public class LocationData {
@SerializedName("userId")
@Expose
private String userId;
@SerializedName("timestamp")
@Expose
private long timestamp;
@SerializedName("longitude")
@Expose
private double longitude;
@SerializedName("latitude")
@Expose
private double latitude;
public LocationData(String userId) {
this.userId = userId;
}
public LocationData(String userId, Location location) {
this.userId = userId;
this.timestamp = location.getTime();
this.latitude = location.getLatitude();
this.longitude = location.getLongitude();
}
}

JSON I got with this has incorrect format without value type like "doubleValue" etc.

{"latitude":19.9802209,"longitude":16.1852646,"timestamp":1599830853181,"userId":"2DBtYfX1uxQszxNmod83"}

I assume POJO class is the only thing I need to change somehow. Or maybe I need to change retrofit.create(PlaceholderApi.class) on something else?

Any suggestions, please.

Thanks.

If you are getting below response from the API

    {
"fields": {
"longitude": {
"doubleValue": 35.5635
},
"latitude": {
"doubleValue": 45.5366
}
}
}

then change your model to something like below.

public class PlacesResponseModel {
@SerializedName("fields")
@Expose
private Fields fields;
public Fields getFields() {
return fields;
}
public void setFields(Fields fields) {
this.fields = fields;
}
}
public class Fields {
@SerializedName("longitude")
@Expose
private Longitude longitude;
@SerializedName("latitude")
@Expose
private Latitude latitude;
public Longitude getLongitude() {
return longitude;
}
public void setLongitude(Longitude longitude) {
this.longitude = longitude;
}
public Latitude getLatitude() {
return latitude;
}
public void setLatitude(Latitude latitude) {
this.latitude = latitude;
}
}
public class Latitude {
@SerializedName("doubleValue")
@Expose
private Double doubleValue;
public Double getDoubleValue() {
return doubleValue;
}
public void setDoubleValue(Double doubleValue) {
this.doubleValue = doubleValue;
}
}
public class Longitude {
@SerializedName("doubleValue")
@Expose
private Double doubleValue;
public Double getDoubleValue() {
return doubleValue;
}
public void setDoubleValue(Double doubleValue) {
this.doubleValue = doubleValue;
}
}

and add it in the retrofit API callback like below.

public interface PlaceholderApi {
@POST("{userId}/documents/{timestamp}")
Call<PlacesResponseModel> saveLocationToCloud(
@Path("userId") String userId,
@Path("timestamp") long timestamp,
@Body LocationData data
);
}

last step call this now, you should get your models mapped