class PortletDefinitionImpl implements IPortletDefinition {
    @Id
    @GeneratedValue(generator = "UP_PORTLET_DEF_GEN")
    @Column(name = "PORTLET_DEF_ID")
    private final long internalPortletDefinitionId;

    @NaturalId
    @Column(name = "PORTLET_FNAME", length = 255, nullable = false)
    private String fname;

    ...
}

        final CriteriaQuery<PortletDefinitionImpl> criteriaQuery = cb.createQuery(PortletDefinitionImpl.class);
        final Root<PortletDefinitionImpl> definitionRoot = criteriaQuery.from(PortletDefinitionImpl.class);
        criteriaQuery.select(definitionRoot);
        criteriaQuery.where(
            cb.equal(definitionRoot.get(PortletDefinitionImpl_.fname), this.fnameParameter)
        );

public <T> NaturalIdQueryBuilder<T> createNaturalIdQuery(Class<T> entityType, String cacheRegion) {
    final Session session = entityManager.unwrap(Session.class);
    return new NaturalIdQueryBuilder<T>(session, entityType, cacheRegion);
}

public static class NaturalIdQueryBuilder<T> {
    private final Class<T> entityType;
    private final Criteria criteria;
    private final NaturalIdentifier naturalIdRestriction;
   
    private NaturalIdQueryBuilder(Session session, Class<T> entityType, String cacheRegion) {
        this.entityType = entityType;
        this.criteria = session.createCriteria(this.entityType);
        this.criteria.setCacheable(true);
        this.criteria.setCacheRegion(cacheRegion);
       
        this.naturalIdRestriction = Restrictions.naturalId();
    }
   
    public <V> NaturalIdQueryBuilder<T> setNaturalIdParam(Attribute<T, V> attribute, V value) {
        final Class<V> valueType = attribute.getJavaType();
        this.naturalIdRestriction.set(attribute.getName(), valueType.cast(value));
        return this;
    }
   
    public T execute() {
        this.criteria.add(this.naturalIdRestriction);
        return this.entityType.cast(criteria.uniqueResult());
    }
}

final NaturalIdQueryBuilder<PortletDefinitionImpl> naturalIdQuery = this.createNaturalIdQuery(PortletDefinitionImpl.class, FIND_PORTLET_DEF_BY_FNAME_CACHE_REGION);
naturalIdQuery.setNaturalIdParam(PortletDefinitionImpl_.fname, fname);

return naturalIdQuery.execute();