import org.springframework.data.domain.AuditorAware;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContextHolder;

public class SpringSecurityAuditor implements AuditorAware<String> {

        @Override
    public String getCurrentAuditor() {

        Authentication authentication = SecurityContextHolder.getContext().getAuthentication();

        if (authentication == null || authentication.getPrincipal().equals("anonymousUser")) {

            return authentication.getPrincipal().toString();
        }

        return ((UsuarioLogado) authentication.getPrincipal()).getUsername();
    }

}

@Override
public Optional<String> getCurrentAuditor() {

    Authentication authentication = SecurityContextHolder.getContext().getAuthentication();

    if (authentication == null || authentication.getPrincipal().equals("anonymousUser")) {

        return (Optional<String>) authentication.getPrincipal();
    }
    return ... código a  ser implementado...
}