Spring服务中的LazyInitializationException

@RequestMapping(value = \"/props\", method = RequestMethod.GET)
public @ResponseBody 
List<Property> getJsonProps(String id) {        
    if(id==null)return null;
    Device dev = deviceService.getDispositivo(Long.parseLong(id));
    List<Property> props = deviceService.listProperties(dev, 10);
    return props;
}

@Service(\"manageDevices\")
@Transactional(readOnly=true,propagation=Propagation.REQUIRED)
public class ManageDevicesImpl implements ManageDevices {

private Logger log = LoggerFactory.getLogger(getClass());

@Autowired
private DevicesDAO devicesDAO; 


    public List<Property> listProperties(Device dev, Integer qty) {
    List<Property> props =  devicesDAO.pickProperties(dev, qty);
    return props; 
    }
}

@Repository(\"devicesDAO\")
public class DevicesDAOImpl implements DevicesDAO {
private Logger log = LoggerFactory.getLogger(getClass()); 

@Autowired
private SessionFactory sessionFactory;

public List<Property> pickProperties(Device dev, Integer qty) {
    if(qty >= 0){           
        log.debug(\"Open? \"+ sessionFactory.getCurrentSession().isOpen());
        log.debug(\"Tx Active? \" + sessionFactory.getCurrentSession().getTransaction().isActive());
        List<Property> props = dev.getProperties();
        if(props != null){
            if(props.size() >= qty)
                return props.subList(0, qty-1);
            else
                return props;
        }
    }
    return null;
}