ServiceGenerator.java

package android.packcargo.com.myapplication.core;

import android.packcargo.com.myapplication.BuildConfig;
import android.packcargo.com.myapplication.core.constant.ServiceConstant;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

import okhttp3.Interceptor;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.logging.HttpLoggingInterceptor;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class ServiceGenerator {

    private static OkHttpClient.Builder httpClient;

    private static Retrofit.Builder builder =
            new Retrofit.Builder()
                    .baseUrl(ServiceConstant.URL_SERVER)
                    .addConverterFactory(GsonConverterFactory.create());

    public static <S> S createService(Class<S> serviceClass) {
        return createService(serviceClass, null);
    }

    public static <S> S createService(Class<S> serviceClass, final String token) {
        if (httpClient == null) {
            httpClient = new OkHttpClient.Builder();

            if (token != null) {
                httpClient.addInterceptor(new Interceptor() {
                    @Override
                    public okhttp3.Response intercept(Chain chain) throws IOException {
                        Request original = chain.request();

                        Request.Builder requestBuilder = original.newBuilder()
                                .header("Accept", "application/json")
                                .header("Authorization", token)
                                .method(original.method(), original.body());

                        Request request = requestBuilder.build();
                        return chain.proceed(request);
                    }
                });
            }

            httpClient.connectTimeout(ServiceConstant.CONNECT_TIMEOUT, TimeUnit.SECONDS)
                    .writeTimeout(ServiceConstant.WRITE_TIMEOUT, TimeUnit.SECONDS)
                    .readTimeout(ServiceConstant.READ_TIMEOUT, TimeUnit.SECONDS)
                    .addInterceptor(addLogging());
        }

        OkHttpClient client = httpClient.build();
        Retrofit retrofit = builder.client(client).build();
        return retrofit.create(serviceClass);
    }

    private static HttpLoggingInterceptor addLogging() {
        HttpLoggingInterceptor logging = new HttpLoggingInterceptor();

        if (BuildConfig.DEBUG) {
            logging.setLevel(HttpLoggingInterceptor.Level.BODY);
        } else {
            logging.setLevel(HttpLoggingInterceptor.Level.BASIC);
        }

        return logging;
    }
}