EDIT

import eu.etaxonomy.cdm.persistence.dto.ClassificationLookupDTO;

    @Override

    public ClassificationLookupDTO classificationLookup(Classification classification) {

        ClassificationLookupDTO classificationLookupDTO = new ClassificationLookupDTO(classification);

        // only for debugging:

//        logger.setLevel(Level.TRACE);

//        Logger.getLogger("org.hibernate.SQL").setLevel(Level.DEBUG);

        String hql = "select t.id, n.rank, tp.id from TaxonNode as tn join tn.classification as c join tn.taxon as t join t.name as n "

                + " left join tn.parent as tnp left join tnp.taxon as tp "

                + " where c = :classification";

        Query query = getSession().createQuery(hql);

        query.setParameter("classification", classification);

        @SuppressWarnings("unchecked")

        List<Object[]> result = query.list();

        for(Object[] row : result) {

            Integer parentId = null;

//            if(row.length == 3) { // TODO check necessary?

//                parentId = (Integer) row[2];

//            }

            classificationLookupDTO.add((Integer)row[0], (Rank)row[1], parentId);

        }

        return classificationLookupDTO ;

    }