if (! teacher.canAddPublicationToTeacherInformationSheet(publication.getPublicationArea())) {
if (teacher != null && !teacher.canAddPublicationToTeacherInformationSheet(publication.getPublicationArea())) {
        public void beforeAdd(Teacher teacher, PublicationTeacher publication) {            if (! teacher.canAddPublicationToTeacherInformationSheet(publication.getPublicationArea())) {                throw new DomainException("error.teacherSheetFull", publication.getPublicationArea().getName());            }        }