Retrofit2, maven project, Illegal reflective access warning

Question

I just started a new maven project and did a simple implementation of the Retrofit client. I'm getting the following warnings:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by retrofit2.Platform (file:/C:/Users/Admin/.m2/repository/com/squareup/retrofit2/retrofit/2.8.1/retrofit-2.8.1.jar) to constructor java.lang.invoke.MethodHandles$Lookup(java.lang.Class,int)
WARNING: Please consider reporting this to the maintainers of retrofit2.Platform
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Process finished with exit code 0

here is the code

import retrofit2.Retrofit;
import retrofit2.SimpleXmlConverterFactory;
import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;

public class RetrofitClient {

    private static Retrofit retrofit = null;
    private RetrofitClient() { }

    public static EndPoints getAPI(String baseUrl) {
        if (retrofit == null) {
            retrofit = new Retrofit.Builder()
                    .baseUrl(baseUrl)
                    .addConverterFactory(SimpleXmlConverterFactory.create())
                    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                    .build();
        }
        return retrofit.create(EndPoints.class);
    }
}

Interface is simply

import retrofit2.Call;
import retrofit2.http.GET;

public interface EndPoints {
    @GET("teststatuses")
    Call<String> testStatus();
}

Call looks like this:

EndPoints endPoints = RetrofitClient.getAPI("http://localhost:8080/");
Call<String> repos = endPoints.testStatus();
System.out.println(repos.execute());

The project runs java language level 11 with SDK 11

Answer 1

There was an issue filed about this, to which one of the Retrofit maintainers responded:

The reflection works around a bug in the JDK which was fixed in 14 but it's only used for default methods. As it's only a warning, it's not preventing your call from working.

So your options are either to

1. stick with Retrofit 2.8.x, and
   • ignore the warning, or
   • upgrade to Java 14
2. downgrade to Retrofit 2.7.*