/** 根据学生ID获取学生信息 */
 @Override
 public MyMessageDTO getMyMessageStudent(String userId) {
   String schoolId = userService.getSchoolId(userId);
   MStudentInfo studentInfo = studentMapper.getStudentInfo(userId, schoolId);
   if (studentInfo == null) {
     throw new MemberException("该学生不存在");
   }
   MyMessageDTO studentInfoDTO = new MyMessageDTO();
   BeanUtils.copyProperties(studentInfo, studentInfoDTO);
   if (studentInfo.getClassId() != null) {
     studentInfoDTO.setClassName(
         ClassNameUtil.getFullName(studentInfo.getYear(), studentInfo.getClassName()));
   }
   return studentInfoDTO;
 }