java.lang.NullPointerException
at stds.jsf.UnitController.CreateDataModel(UnitController.java:119)
at stds.jsf.UnitController.getItems(UnitController.java:112)

public DataModel CreateDataModel (){
    return new ListDataModel(Dao.getAllUnits());
}

public DataModel getItems() {
    if (items == null) {
    items = CreateDataModel();
    } else {
    }
    return items;
}

public List<Unit> getAllUnits() {
    List<Unit> units = null;
    Transaction trns = null;
    Session session = HibernateUtil.getSessionFactory().openSession();
    try {
        trns = session.beginTransaction();
        units = session.createQuery("From Unit").list();
    } catch (RuntimeException e) {
        e.printStackTrace();
    } finally {
        session.flush();
        session.close();
    }
    return units;
}