Why am I getting a null value onNext in RxJava? (rxjava2 + retrofit2)

Question

This is the interface:

@GET("solicitation/get/{protocol}")
Observable<Solicitation> getProtocol(@Path("protocol") String protocol, @Query("X-Authorization") String apiKey);

And this is in my ApiClient class,

    if (retrofit==null) {
        retrofit = new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .client(httpClient.build())
                .build();

This is how I call it on my MainActivity onCreate:

    ApiInterface apiService = ApiClient.getClient().create(ApiInterface.class);

    apiService.getProtocol("2313868283", getResources().getString(R.string.api_key))
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(obSol);

And this is outside of onCreate:

Observer<Solicitation> obSol  = new Observer<Solicitation>() {

    @Override
    public void onSubscribe(@NonNull Disposable d) {
        Log.e(TAG, "onSubscribe" + Thread.currentThread().getName());
    }

    @Override
    public void onNext(@NonNull Solicitation solicitation) {
        Log.e(TAG, "onNext: " + solicitation.getName() + " " + Thread.currentThread().getName());
    }

    @Override
    public void onError(@NonNull Throwable e) {
        Log.e(TAG, "onError: " + e.toString());
    }

    @Override
    public void onComplete() {
        Log.e(TAG, "onComplete: All Done!" + Thread.currentThread().getName());
    }
};

When I run the app retrofit does its magic, yanks the results out of that api call and everything, except I get null where I should've gotten the actual result:

        06-11 12:26:31.691 22760-22760/com.example.ga.myapplication E/lol: onSubscribemain
        06-11 12:26:31.704 22760-22798/com.example.ga.myapplication D/OkHttp: --> GET (URL HIDDEN FOR THIS POST) http/1.1
        06-11 12:26:31.704 22760-22798/com.example.ga.myapplication D/OkHttp: --> END GET
        06-11 12:26:31.814 22760-22801/com.example.ga.myapplication I/OpenGLRenderer: Initialized EGL, version 1.4
        06-11 12:26:31.814 22760-22801/com.example.ga.myapplication D/OpenGLRenderer: Swap behavior 1
        06-11 12:26:31.814 22760-22801/com.example.ga.myapplication W/OpenGLRenderer: Failed to choose config with EGL_SWAP_BEHAVIOR_PRESERVED, retrying without...
        06-11 12:26:31.814 22760-22801/com.example.ga.myapplication D/OpenGLRenderer: Swap behavior 0
        06-11 12:26:32.054 22760-22760/com.example.ga.myapplication W/art: Before Android 4.1, method int android.support.v7.widget.ListViewCompat.lookForSelectablePosition(int, boolean) would have incorrectly overridden the package-private method in android.widget.ListView
        06-11 12:26:32.511 22760-22798/com.example.ga.myapplication D/OkHttp: <-- 200 OK (URL HIDDEN FOR THIS POST) (807ms)
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Date: Sun, 11 Jun 2017 15:40:51 GMT
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Server: Apache/2.4.18 (Ubuntu)
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Access-Control-Allow-Origin: *
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Access-Control-Allow-Methods: GET, POST, OPTIONS
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Access-Control-Allow-Headers: Origin, Content-Type, Accept, Authorization, X-Request-With
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Access-Control-Allow-Credentials: true
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Cache-Control: no-cache
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Set-Cookie: XSRF-TOKEN=ADA1ODc0MWRlNWZlOWM0MjJhYWNkMTc1OGZjMzk2ZDhlOGJhNTZlZDRhM2RmN2ZjMzk0NjFmOTdmIn0%3D; expires=Sun, 11-Jun-2017 17:40:51 GMT; Max-Age=7200; path=/
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Set-Cookie: laravel_session=eiUADHiuhsaduihAIUSDVuRWpacDR4Mm5wSzljNnc0YzJ5dFBBQ2NDU5ZTFmYjg3ZmM3ZiJ9; expires=Sun, 11-Jun-2017 17:40:51 GMT; Max-Age=7200; path=/; HttpOnly
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Content-Length: 329
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Keep-Alive: timeout=5, max=100
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Connection: Keep-Alive
        06-11 12:26:32.512 22760-22798/com.example.ga.myapplication D/OkHttp: Content-Type: application/json
        06-11 12:26:32.514 22760-22798/com.example.ga.myapplication D/OkHttp: {"data":[{"id":5,"name":"Roll D","protocol":"2313868283"}]}
        06-11 12:26:32.514 22760-22798/com.example.ga.myapplication D/OkHttp: <-- END HTTP (329-byte body)
        06-11 12:26:32.520 22760-22760/com.example.ga.myapplication E/lol: onNext: null main
        06-11 12:26:32.520 22760-22760/com.example.ga.myapplication E/lol: onComplete: All Done!main

Edit:

To make it a little clearer this is the call onNext:

Log.e(TAG, "onNext: " + solicitation.getName() + " " + Thread.currentThread().getName());

And this is the log:

        06-11 12:26:32.520 22760-22760/com.example.ga.myapplication E/lol: onNext: null main

Answer 1

It is null because the JSON returned by the webservice cannot be mapped into your Solicitation class.

Looking at the JSON logged you need to replace the Solicitation with the following class:

class ApiResponse {
    List<Solicitation> data;
}

Since the API returns an object that contains a list of Solicitation.