@Override
  public void registerReferenceProviders(@NotNull final PsiReferenceRegistrar registrar) {
    final JavaClassListReferenceProvider classListProvider = new JavaClassListReferenceProvider();
    registrar.registerReferenceProvider(xmlAttributeValue(), classListProvider, PsiReferenceRegistrar.LOWER_PRIORITY);
    registrar.registerReferenceProvider(xmlTag(), classListProvider, PsiReferenceRegistrar.LOWER_PRIORITY);
  }
@Override
  public void registerReferenceProviders(@NotNull final PsiReferenceRegistrar registrar)