@Override
  public ClazzDetail addClazzDetail(int classID, int studentID) {
    Clazz clazz = em.find(Clazz.class, classID);
    Student student = em.find(Student.class, studentID);

    if ((clazz != null) && (student != null)) {
      ClazzDetail cd = new ClazzDetail();
      cd.setClazz(clazz);
      cd.setStudent(student);

      return this.persistClazzDetail(cd);
    }
    return null;
  }
 public ClazzDetail mergeClazzDetail(ClazzDetail clazzDetail) {
   try {
     ClazzDetail cd = em.find(ClazzDetail.class, clazzDetail.getClazz_DETAIL_ID());
     cd.setClazz(clazzDetail.getClazz());
     cd.setClazz_DETAIL_ID(clazzDetail.getClazz_DETAIL_ID());
     cd.setStudent(clazzDetail.getStudent());
     return em.merge(cd);
   } catch (Exception e) {
     throw new EJBException(e.getMessage());
   }
 }