How to send multiple query parameters of same name with Retrofit

RestClient.java

import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import okhttp3.HttpUrl;
import okhttp3.HttpUrl.Builder;
import okhttp3.Interceptor;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import retrofit2.Retrofit;

public class RestClient {

  private static final String BASE_URL = "www.base.com";

  public static <T> T create(Class<T> apiInterfaceClass, Map<String, List<String>> queries) {
    Retrofit retrofit = new Retrofit.Builder()
        .baseUrl(BASE_URL)
        .client(okHttpClient(queries))
        .build();
    return retrofit.create(apiInterfaceClass);
  }

  private static OkHttpClient okHttpClient(Map<String, List<String>> queries) {
    return new OkHttpClient.Builder()
        .addInterceptor(makeQueriesInterceptor(queries))
        .build();
  }

  private static Interceptor makeQueriesInterceptor(Map<String, List<String>> queries) {
    return chain -> {
      HttpUrl url = addQueryParametersToUrl(chain.request().url(), queries);
      Request request = chain.request().newBuilder().url(url).build();
      return chain.proceed(request);
    };
  }

  private static HttpUrl addQueryParametersToUrl(HttpUrl url, Map<String, List<String>> queries) {
    HttpUrl.Builder builder = url.newBuilder();
    for (Entry<String, List<String>> entry : queries.entrySet()) {
      addQueryParameters(builder, entry);
    }
    return builder.build();
  }

  private static void addQueryParameters(Builder builder, Entry<String, List<String>> entry) {
    String key = entry.getKey();
    List<String> value = entry.getValue();
    for (String option : value) {
      builder.addQueryParameter(key, option);
    }
  }
}

how to use

create an instance of your api service via the above create() method and pass in the dynamic query parameters:

ApiService service = RestClient.create(ApiService.class, queries);

where ApiService is any retrofit interface 👯

Thanks, This is what I exactly needed

Thank you, Amanda!
helpful and easy-to-use.

I would like to change only ine thing - pass base_url as an argument in create() method.