Java Spring MVC 数据库异常未获取

Question

在我的 spring 项目中，我想将学生信息保存在 mysql 数据库中。如果有任何错误，则会显示在jsp页面中相应的输入框中。

所以，我有:-

StudentDao 类

public interface StudentDao {
    public void add ( Student student );
    }

StudentDaoImpl 类

public class StudentDaoImpl implements StudentDao {

    @Autowired
    private SessionFactory sessionFactory;

     public void setSessionFactory(SessionFactory sessionFactory){
            this.sessionFactory = sessionFactory;
        }

    public void add( Student student){
        sessionFactory.getCurrentSession().save(student);
    }}

StudentService 类

public interface StudentService {
        Student add(String name, String email) throws SQLException, 
                                                   DataAccessException,
                                                   DataIntegrityViolationException,
                                                   ConstraintViolationException{
}

StudentServiceImpl类

public class StudentServiceImpl implements StudentService {


    @Autowired
    private StudentDao studentDao;

    @Transactional(propagation = Propagation.REQUIRED)
    public Student add(String name, String email) throws SQLException, 
                                                   DataAccessException,
                                                   DataIntegrityViolationException,
                                                   ConstraintViolationException{


    Student student = new Student(name,email);
        studentDao.add(student);

        return student;
            }

}

Controller 类

@RequestMapping(value = "/add", method = RequestMethod.POST)
    public String doAdd(@Valid @ModelAttribute("student") Student student,BindingResult result,HttpServletRequest request,
            HttpServletResponse response,Model model){

        validator.validate(student, result);
         if (result.hasErrors()) {

                return "signup";
            }

                @SuppressWarnings("unused")
                Student student1;

                 try{   
                try {
                    student1= studentService.add(student.getName(), student.getEmail());
                } catch (ConstraintViolationException e) {

                    model.addAttribute("email", "already exists");
                    e.printStackTrace();
                     return "signup";
                } catch (DataAccessException e) {

                    model.addAttribute("email", "already exists");
                    e.printStackTrace();
                     return "signup";
                } catch (SQLException e) {

                    model.addAttribute("email", "already exists");
                    e.printStackTrace();
                     return "signup";
                }
                 }catch (DataIntegrityViolationException e) 
                 {
                        model.addAttribute("email", "already exists");

                        e.printStackTrace();
                         return "signup";

                 }

        return "signup";
    }

但问题是我的数据库电子邮件字段是唯一的。因此，对于重复条目，我收到日志消息:

 WARN JDBCExceptionReporter:100 - SQL Error: 1062, SQLState: 23000
  JDBCExceptionReporter:101 - Duplicate entry 'df@gmail.com' for key 'unique_index2'
org.hibernate.exception.ConstraintViolationException: could not insert: [com.myweb.model.Student]
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'df@gmail.com' for key 'unique_index2'

我想将此错误放置到 jsp View 电子邮件字段中，电子邮件已存在我在服务类中使用了 throws block ，并在 Controller 类中使用了 try-catch block ..尽管为什么错误没有显示在jsp View ？

Answer 1

所以，你正在使用 spring 和 hibernate ..异常(exception)是:ConstraintViolationException 这就是为什么它:

org.hibernate.exception.ConstraintViolationException

只需添加:

<h1>${email}</h1>

您可以使用其他标签来显示该消息。