android retrofit post request - exclude field from the body

Question

I am writing and android add and using retrofit2 to send data to the server.

I am trying to exclude one field from the the object that is being serialized and sent to the server.

The object is named "Cheer" and I try to exclude the field id from it when being sent to the server. iv'e tried using @Expose(false, false) and explained here and tried to make the field private, but it is still sent to the server. See the api, object and call below. Please note, it workes, the object is added to the server, the only issue is that, id is still sent in the JSON and I need to exclude it from it.

Thanks!!!

public class Cheer {
    @Expose(deserialize = false, serialize = false)
    private int id;
}





public interface CheersAPI {

    String BASE_URL = "url:port";

    @POST("/cheers")
    Call<Cheer> AddCheer(@Body Cheer cheer);
}



cheersAPI.AddCheer(cheerToAdd).enqueue(new Callback<Cheer>(){
                            @Override
                            public void onResponse(Call<Cheer> call, Response<Cheer> response) {
                                Log.d("in the on response", "done creating a cheer");
                            }

                            @Override
                            public void onFailure(Call<Cheer> call, Throwable t) {
                                Log.d("failed", "failed to add a cheer here!");
                            }


                        });

Answer 1

This is how to do it with Retrofit

    val gson: Gson = GsonBuilder().excludeFieldsWithoutExposeAnnotation().create()

    builder = Retrofit.Builder()
            .client(okHttpClient)
            .baseUrl(URL)
            .addConverterFactory(GsonConverterFactory.create(gson))
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())

And in your model

// These values are read as JSON objects only in server response
@SerializedName("someField")
@Expose(serialize = false, deserialize = true)
var someField: String? = null

For example here, we will not send JSON object to server (deserialize = false) but we will receive it as response (deserialize = true)

Answer 2

Visit here for details.

Basically, @Expose will not be regarded by the default Gson instance. In order to utilize it, you'll need to use a custom Gson instance:

GsonBuilder builder = new GsonBuilder();  
builder.excludeFieldsWithoutExposeAnnotation();  
Gson gson = builder.create();  

but if you do this you'll have to add @Expose to every field in all your model classes or they won't be serialised or deserialised by GSON.