I want to make a PATCH process :

@Path("/calendrier-serveur")
    @PATCH
    @Produces(MediaType.APPLICATION_JSON)
    public Response updateCalendrierServeur(TPosCalendrierServeur data) {
        try {
            TPosCalendrierServeur newData = service.updateCalendrierServeur(data);
            return Response.ok(newData, MediaType.APPLICATION_JSON).build();
        } catch (IllegalAccessException | InvocationTargetException e) {
            LOGGER.error("Error occured while updating server calendar." + e.getStackTrace());
            Payload payload = new Payload("Invalid payload.",e.getMessage());
            return Response.status(Response.Status.BAD_REQUEST).entity(payload).build();
        }
    }

code of the service :

...
import org.apache.commons.beanutils.BeanUtilsBean;
...
@Transactional
    public TPosCalendrierServeur updateCalendrierServeur(TPosCalendrierServeur data) throws IllegalAccessException, InvocationTargetException {
        TPosCalendrierServeur original = calendrierServeurRepository.find("mmcUserId = ?1", data.getMmcUserId()).firstResult();
            BeanUtilsBean beanUtil = new NullAwareBeanUtilsBean();
            beanUtil.copyProperties(original, data);
            calendrierServeurRepository.getEntityManager().merge(original);
            original = calendrierServeurRepository.find("mmcUserId = ?1", data.getMmcUserId()).firstResult();
            return original;
    }

I debugged the data when calling the service and I get data.getAbsenceDebut() = null before the copyProperties , but after the copyProperties then it remains the data of the original object from database.

So why is the property not set to null ?