Registry registry = new Registry();
Strategy strategy = new RegistryStrategy(registry);
Serializer serializer = new Persister(strategy);
registry.bind(User.class, new UserConverter(usersDao, usersMap));
registry.bind(Appointment.class, new AppointmentConverter(appointmentDao, appointmentsMap));
List<MeetingMember> list = readList(serializer, f, "meetingmembers.xml", "meetingmembers", MeetingMember.class);
for (MeetingMember ma : list) {
if (ma.getUserid() != null && ma.getUserid().getUser_id() == null) {
ma.setUserid(null);