public static boolean demanderVoyance(Voyance voy){
        if (voy==null) { return false; }

        JpaUtil.creerEntityManager();
        JpaUtil.ouvrirTransaction();

        EmployeDAO employeDAO = new EmployeDAO();
        VoyanceDAO voyanceDAO = new VoyanceDAO();
        voyanceDAO.persistVoyance(voy);
        List<Employe> emps = voy.getMedium().getIncarnations();
        Employe e=null;
        Integer size = Integer.MAX_VALUE;
        for(Employe emp : emps){
            List<Voyance> voys = voyanceDAO.historiqueEmploye(emp);
            if(voys.size()<size && !emp.estOccupe()){
                e = emp;
                size = voys.size();
            }
        }
        if (e!=null){
            voy.setEmploye(e);
            e.setVoyance(voy);
            try {
                employeDAO.mergeEmploye(e);
                voyanceDAO.mergeVoyance(voy);

                JpaUtil.validerTransaction();
            } catch(Exception exc){
                JpaUtil.annulerTransaction();
                voy.setEmploye(null);
                e.setVoyance(null);
                e=null;
            }
        } else {
            JpaUtil.annulerTransaction();
        }
        JpaUtil.fermerEntityManager();
        return e!=null;
    }