java方法返回空值

Question

在使用 Spring MVC 做项目时。基本是：当学生注册时，他的数据将存储在数据库表中，并将密码发送到学生的邮件地址。

所以我有：

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

    studentService.addNewStudent(student.getName(),
        student.getUsername(), student.getEmail(), student.getPassword());
    studentService.sendEmail(student);
}

StudentDao接口是：

public interface StudentDao {
    public void saveStudent(Student student);
    public void fetchinfo(Student student);
}

StudentDaoImpl 中的fetchinfo 实现是：

public void fetchinfo(Student student) {
    String hql = "select password from student where email = :email";
    sessionFactory.getCurrentSession().createSQLQuery(hql)
        .setParameter("email", student.getEmail()).uniqueResult();
}

StudentService接口是：

public interface StudentService {
    Student addNewStudent(String name, String username, String email, String password);
    void sendEmail(Student student);
    Student fetchinfo(String email);
}

而StudentServiceImpl 是：

public User fetchinfo(String email) {
    Student student = new Student(email);
    studentDao.fetchinfo(student);
    return student;
}

public void sendEmail(Student student) {
    mailService.accountActivation(student);
}

现在，问题是：一封邮件被发送到学生的邮件地址，但密码是null。有人可以解释为什么会这样吗？

Answer 1

在StudentDaoImpl 中，您没有从数据库查询结果中设置密码属性。将相关行改写为：

student.setPassword(sessionFactory.getCurrentSession().createSQLQuery(hql)
    .setParameter("email", student.getEmail()).uniqueResult());

更新

当我们在 Hibernate 中时，按照惯例，Student 实体应该有每个属性的 getter 和 setter。然后我将StudentDaoImpl重写为：

public void fetchinfo(String email) {

    String hql = "select s from student s where s.email = :email";

    return (Student)sessionFactory.getCurrentSession().createSQLQuery(hql)
      .setParameter("email", email).uniqueResult();

}

..并用student = studentDao.fetchinfo(email); 调用它（当然方法的命名应该改变）。