@Converter(autoApply = true)
public static class YearMonthAttributeConverter
		implements AttributeConverter<YearMonth, Integer> {

	@Override
	public Integer convertToDatabaseColumn(YearMonth attribute) {
		return (attribute.getYear() * 100) + attribute.getMonth().getValue();
	}

	@Override
	public YearMonth convertToEntityAttribute(Integer dbData) {
		return YearMonth.of(dbData / 100, dbData % 100);
	}
}

options.put(
		EntityManagerFactoryBuilderImpl.METADATA_BUILDER_CONTRIBUTOR,
		(MetadataBuilderContributor) metadataBuilder ->
				metadataBuilder.applyAttributeConverter( YearMonthAttributeConverter.class )
);