使用HibernateTemplate（）删除List <object>会产生异常</object>

Question

我正在尝试从表FlexiBooking中获取List，然后将其添加到另一个列表，即移动到另一个表并删除从该表中获取的那些条目。我使用了HibernateTemplate（）对象，因为项目是使用Spring Framework完成的。但是我试图删除Detatched对象时遇到异常。问题是什么？  以下是我的代码：

    @Override
public void moveToNormalBooking(User user,
        int no_of_seats) {
    String queryString  = "FROM FlexiBooking";
    HibernateTemplate hibernateTemplate = getHibernateTemplate();
    hibernateTemplate.setMaxResults(no_of_seats);
    List<FlexiBooking> flexiBookingsTobeMoved = hibernateTemplate.find(queryString);
    List<FlightBooking> flightBookings = new ArrayList<FlightBooking>(); 
    int i =0; 
    while(i < flexiBookingsTobeMoved.size()) {
        FlightBooking flightbooking = new FlightBooking();
        flightbooking.setCostPerTicket(flexiBookingsTobeMoved.get(i).getTotalCost());
        flightbooking.setDateOfJourney(flexiBookingsTobeMoved.get(i).getScheduledFlight().getScheduledFlightDate());
        Booking booking = new Booking();
        booking.setBooker(flexiBookingsTobeMoved.get(i).getUser());
        booking.setBookingDate(flexiBookingsTobeMoved.get(i).getBookingDate());
        booking.setBookingReferenceNo(flexiBookingsTobeMoved.get(i).getBookingReferenceNumber());
        booking.setCancelled(false);
        flightbooking.setBooking(booking);
        flightbooking.setFlightRoute(flexiBookingsTobeMoved.get(i).getScheduledFlight());
        flightbooking.setCouponCode(flexiBookingsTobeMoved.get(i).getCouponCode());
        flightBookings.add(flightbooking);
        i++;
    }
    hibernateTemplate.saveOrUpdateAll(flightBookings);
 //   hibernateTemplate.update(flexiBookingsTobeMoved);
    hibernateTemplate.deleteAll(flexiBookingsTobeMoved);
}