List<Appointment> list = appointmentDao.getAppointments();
Registry registry = new Registry();
Strategy strategy = new RegistryStrategy(registry);
Serializer serializer = new Persister(strategy);
registry.bind(AppointmentCategory.class, AppointmentCategoryConverter.class);
registry.bind(User.class, UserConverter.class);
registry.bind(AppointmentReminderTyps.class, AppointmentReminderTypeConverter.class);
registry.bind(Room.class, RoomConverter.class);
if (list != null && list.size() > 0) {
registry.bind(list.get(0).getAppointmentStarttime().getClass(), DateConverter.class);