how to use retrofit 2 to send file and other params together

Question

I am looking for an example how could I send file and other params together to server.

I have to send server JSON which

{
    "title": "title",
    "file": "uploaded file instance",
    "location": {
        "lat": 48.8583,
        "lng": 2.29232,
        "place": "Eiffel Tower"
    }
}

How could I create Retrofit to handle this case?

If file is a string I know how to handle this. If file is File object I have no idea how to do this.

Answer 1

Use gson and create a model class for the location.

Add the following dependencies to your build.gradle.

compile 'com.squareup.retrofit2:converter-gson:2.0.0'
compile 'com.google.code.gson:gson:2.5'

Create a model to represent the location.

public class Location {

    double lat;
    double lng;
    String location;

    public Location(double lat, double lon, String place) {
        this.lat = lat;
        this.lon = long;
        this.place = place;
    } 

}

If the variable names for the payload fields don't match the actual required name for the endpoint you will need to add the annotation @SerializedName([expected name])

ex:

import com.google.gson.annotations.SerializedName;

public class Location {

    @SerializedName("lat")
    double latitude;
    @SerializedName("lng")
    double longitude;
    @SerializedName("place")
    String location;

    public Location(double lat, double lon, String place) {
        latitude = lat;
        longitude = long;
        location = place;
    } 

}

Define the api interface.

public interface Api {

    @POST("upload/")
    @Multipart
    Call<ResponseBody> uploadFile(@Part("title") RequestBody title,
                                  @Part MultipartBody.Part imageFile,
                                  @Part("location") Location location
    );

}

Create a Retrofit instance and call the api.

File file;
// create retrofit instance
Retrofit retrofit = new Retrofit.Builder()
        .baseUrl("https://baseurl.com/api/")
        .addConverterFactory(GsonConverterFactory.create())
        .build();
// create api instance
Api api = retrofit.create(Api.class);
// create call object
Call<ResponseBody> uploadFileCall = api.uploadFile(
        RequestBody.create(MediaType.parse("text/plain"), "title"),
        MultipartBody.Part.createFormData(
            "file",
            file.getName(),
            RequestBody.create(MediaType.parse("image"), file)),
        new Location(48.8583, 2.29232, "Eiffel Tower"));
// sync call
try {
    ResponseBody responseBody = uploadFileCall.execute().body();
} catch (IOException e) {
    e.printStackTrace();
}
// async call
uploadFileCall.enqueue(new Callback<ResponseBody>() {
    @Override
    public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
        if (response.isSuccessful()) {
            // TODO
        }
    }

    @Override
    public void onFailure(Call<ResponseBody> call, Throwable t) {
        // TODO
    }
});

You will need to change the MediaType.parse() call if you are not using an image file.

You can similarly create a custom response type object and replace ResponseBody with it to receive a deserialized result object.

Let me know if this works. I didn't have a chance to test in your exact scenario obviously but I'm fairly confident this should work. The only part I'm not 100% on is whether @Part("location") Location location should be @Body("location") Location location