How to add Authorization header in retrofit call using Dagger 2

Question

I have a working code example of Token Based Api Authentication(Laravel Passport), but it's without Dagger 2. I want to move code from current RetrofitBuilder.java to AppModule, so that I can use the power of the Dagger 2 in the app.

For Now, Without Dagger Dependency, I have two static methods in RetrofitBuilder.java which could be used for authenticated routes calls and unauthenticated routes calls:

1) createService(service) // Which makes API call without Authorization Headers (without Access Token)

2) createServiceWithAuth(service, tokenManager) // Which makes API call with Authorization Headers e.g with Access Token

How to achieve same functionality using Dagger dependency. How can I achieve providing these above two methods to my business logic class e.g UserRepository.java so that I can make authenticated and unauthenticated service calls any where it is necessary.

RetrofitBuilder.java

public class RetrofitBuilder {

    private static final String BASE_URL = "https://api.com/";

    private final static OkHttpClient client = buildClient();
    private final static Retrofit retrofit = buildRetrofit(client);

    private static OkHttpClient buildClient(){
        OkHttpClient.Builder builder = new OkHttpClient.Builder()
                .addInterceptor(new Interceptor() {
                    @Override
                    public Response intercept(Chain chain) throws IOException {
                        Request request = chain.request();

                        Request.Builder builder = request.newBuilder()
                                .addHeader("Accept", "application/json")
                                .addHeader("Connection", "close");

                        request = builder.build();

                        return chain.proceed(request);

                    }
                });

        if(BuildConfig.DEBUG){
            builder.addNetworkInterceptor(new StethoInterceptor());
        }

        return builder.build();

    }

    private static Retrofit buildRetrofit(OkHttpClient client){
        return new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .client(client)
                .addConverterFactory(MoshiConverterFactory.create())
                .build();
    }

    public static <T> T createService(Class<T> service){
        return retrofit.create(service);
    }

    public static <T> T createServiceWithAuth(Class<T> service, final TokenManager tokenManager){

        OkHttpClient newClient = client.newBuilder().addInterceptor(new Interceptor() {
            @Override
            public Response intercept(Chain chain) throws IOException {

                Request request = chain.request();

                Request.Builder builder = request.newBuilder();

                if(tokenManager.getToken().getAccessToken() != null){
                    builder.addHeader("Authorization", "Bearer " + tokenManager.getToken().getAccessToken());
                }
                request = builder.build();
                return chain.proceed(request);
            }
        }).authenticator(CustomAuthenticator.getInstance(tokenManager)).build();

        Retrofit newRetrofit = retrofit.newBuilder().client(newClient).build();
        return newRetrofit.create(service);

    }

    public static Retrofit getRetrofit() {
        return retrofit;
    }
}

CustomAuthenticator.java (it refresh the token if the access token is expired)

public class CustomAuthenticator implements Authenticator {

    private TokenManager tokenManager;
    private static CustomAuthenticator INSTANCE;

    private CustomAuthenticator(TokenManager tokenManager){
        this.tokenManager = tokenManager;
    }

    static synchronized CustomAuthenticator getInstance(TokenManager tokenManager){
        if(INSTANCE == null){
            INSTANCE = new CustomAuthenticator(tokenManager);
        }

        return INSTANCE;
    }


    @Nullable
    @Override
    public Request authenticate(Route route, Response response) throws IOException {

        if(responseCount(response) >= 3){
            return null;
        }

        AccessToken token = tokenManager.getToken();

        ApiService service = RetrofitBuilder.createService(ApiService.class);
        Call<AccessToken> call = service.refresh(token.getRefreshToken() + "a");
        retrofit2.Response<AccessToken> res = call.execute();

        if(res.isSuccessful()){
            AccessToken newToken = res.body();
            tokenManager.saveToken(newToken);

            return response.request().newBuilder().header("Authorization", "Bearer " + res.body().getAccessToken()).build();
        }else{
            return null;
        }
    }

    private int responseCount(Response response) {
        int result = 1;
        while ((response = response.priorResponse()) != null) {
            result++;
        }
        return result;
    }
}

AppModule.java

@Module(includes = ViewModelModule.class)
public class AppModule {

    // --- DATABASE INJECTION ---

    @Provides
    @Singleton
    MyDatabase provideDatabase(Application application) {
        return Room.databaseBuilder(application,
                MyDatabase.class, "MyDatabase.db")
                .build();
    }

    @Provides
    @Singleton
    UserDao provideUserDao(MyDatabase database) { return database.userDao(); }

    // --- REPOSITORY INJECTION ---

    @Provides
    Executor provideExecutor() {
        return Executors.newSingleThreadExecutor();
    }

    @Provides
    @Singleton
    UserRepository provideUserRepository(UserWebservice webservice, UserDao userDao, Executor executor) {
        return new UserRepository(webservice, userDao, executor);
    }

    // --- NETWORK INJECTION ---

    private static String BASE_URL = "https://api.com/";

    @Provides
    Gson provideGson() { return new GsonBuilder().create(); }

    @Provides
    Retrofit provideRetrofit(Gson gson) {
        Retrofit retrofit = new Retrofit.Builder()
                .addConverterFactory(GsonConverterFactory.create(gson))
                .baseUrl(BASE_URL)
                .build();
        return retrofit;
    }

    @Provides
    @Singleton
    UserWebservice provideApiWebservice(Retrofit restAdapter) {
        return restAdapter.create(UserWebservice.class);
    }
}

Answer 1

You can move the creation of okHttp and retrofit to your Dagger Module and then assign it to the service constructor you need it for.

In code something like:

@Module
public class ServiceModule {
    @Provides
    @Singleton
    OkHttp provideOkHttp(Authenticator authenticator) {
        OkHttpClient.Builder builder = new OkHttpClient.Builder()
            .addInterceptor(new Interceptor() {
                @Override
                public Response intercept(Chain chain) throws IOException {
                    Request request = chain.request();
                    Request.Builder builder = request.newBuilder()
                            .addHeader("Accept", "application/json")
                            .addHeader("Connection", "close");

                    request = builder.build();
                    return chain.proceed(request);
                }
            });

        if (BuildConfig.DEBUG) {
            builder.addNetworkInterceptor(new StethoInterceptor());
        }

        // build this authenticator in the same way as all the other dependencies shown here
        builder.authenticator(authenticator);

        return builder.build();
    }

    @Provides
    @Singleton
    Retrofit provideRetrofit(OkHttp okHttp) {
        return new Retrofit.Builder()
            .baseUrl(BASE_URL)
            .client(okHttp)
            .addConverterFactory(MoshiConverterFactory.create())
            .build();
    }

    @Provides
    @Singleton
    Service provideService(Retrofit retrofit) {
        return new ServiceImpl(retrofit);
    }
}

Code is not tested though...