/** return all marks for a given  parameter **/
    public String marksByField() {
        System.out.println("----> i AM IN <------");
        String redirect = null;
        // get student num or course num
        ExternalContext context =
                FacesContext.getCurrentInstance().getExternalContext();
        HttpServletRequest request =
                (HttpServletRequest)context.getRequest();
        String studentnum = request.getParameter("marksByStudentForm:selectOneStudent");
        String coursenum = request.getParameter("marksByCourseForm:selectOneCourse");
        // 
        String colName;
        String fiedlValue;
        if (studentnum != null) {
            colName = "student";
            fiedlValue = studentnum;  
            System.out.println("--> STUD " + studentnum);
            redirect = "reportstudent";
        }
        else {
            colName = "course";
            fiedlValue = coursenum;
            System.out.println("--> STUD " + coursenum);
            redirect = "reportcourse";
        }
        EntityManager em = getEntityManager();
        try{
            Query q = em.createQuery("select object(o) from Marks where "+ colName + "=" + fiedlValue + " as o");
            q.setMaxResults(batchSize);
            q.setFirstResult(firstItem);
            myModel = new ListDataModel(q.getResultList());
          
        } finally {
            em.close();
        }
        return redirect;
    }