class MetadataDao extends NamedParameterJdbcDaoSupport {

    public Set<String> loadMetadataKeys(final AclClass entityClass) {
        final List<String> result = ListUtils.emptyIfNull(
                getJdbcTemplate()
                        .queryForList(loadMetadataKeysQuery, String.class, entityClass.name()));
        return new HashSet<>(result);
    }

}