if (studentNumber == null && StringUtils.isNumeric(studentNumber)) {
if (studentNumber == null || !StringUtils.isNumeric(studentNumber)) {
    private String getStudent(HttpServletRequest request) {        String studentNumber = request.getParameter("studentNumber");        if (studentNumber == null && StringUtils.isNumeric(studentNumber)) {            studentNumber = (String) request.getAttribute("studentNumber");        }        return studentNumber;    }