Retrofit ApiModule I frequently use to provide custom app-level http caching

ApiModule.java

package io.quantus.winterinantwerpen.api;

import android.content.Context;
import android.location.LocationManager;
import android.util.Log;

import com.squareup.okhttp.Cache;
import com.squareup.okhttp.Interceptor;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;

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

import javax.inject.Singleton;

import dagger.Module;
import dagger.Provides;
import io.quantus.winterinantwerpen.language.LanguageManager;
import io.quantus.winterinantwerpen.util.ConnectivityHelper;
import retrofit.GsonConverterFactory;
import retrofit.Retrofit;
import retrofit.RxJavaCallAdapterFactory;

@Module
public class ApiModule {

    @Provides
    ApiService provideApiService(Context context, LanguageManager languageManager) {

        OkHttpClient client = new OkHttpClient();
        Cache responseCache = new Cache(new File(context.getCacheDir(), "http"), 1024 * 1024 * 10); // 10 MB cache size
        client.setCache(responseCache);

        client.setConnectTimeout(30, TimeUnit.SECONDS);
        client.setReadTimeout(30, TimeUnit.SECONDS);

        client.networkInterceptors().add(mCacheControlInterceptor);

        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(String.format("https://api.winterapp.be/%s/", languageManager.getLocale()))
                .addConverterFactory(GsonConverterFactory.create())
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .client(client)
                .build();

        return retrofit.create(ApiService.class);
    }

    private static final Interceptor mCacheControlInterceptor = new Interceptor() {
        @Override
        public Response intercept(Chain chain) throws IOException {
            Request request = chain.request();

            // Add Cache Control only for GET methods
            if (request.method().equals("GET")) {
                if (ConnectivityHelper.isConnected()) {
                    Log.d("CacheControlInterceptor", "intercept connected");
                    // 1 day
                    request.newBuilder()
                            .header("Cache-Control", "only-if-cached")
                            .build();
                } else {
                    Log.d("CacheControlInterceptor", "intercept not connected");
                    // 4 weeks stale
                    request.newBuilder()
                            .header("Cache-Control", "public, max-stale=2419200")
                            .build();
                }
            }

            Response response = chain.proceed(request);

            // Re-write response CC header to force use of cache
            return response.newBuilder()
                    .header("Cache-Control", "public, max-age=86400") // 1 day
                    .header("Pragma", "public")
                    .build();
        }
    };
}