java.lang.ClassCastException：org.hibernate.internal.QueryImpl无法转换为com.models.User

Question

I have a user table structured this way

id    name     email
1     cc       cc@yahoo.com
2     rr       rr@yahoo.com
3     cc       cc@yahoo.com

I am writing a query to save a log when ever it finds an email matching any of the row with the below hql

String hql = "FROM User c WHERE c.email = :email order by c.id";
        return (User) _sessionFactory.getCurrentSession().createQuery(hql).setParameter("email", email);

When I run my code I get this error

java.lang.ClassCastException: org.hibernate.internal.QueryImpl cannot be cast to com.models.User
    at com.models.UserDao.getByEmail(UserDao.java:62)

Answer 1

You forgot to call uniqueResult() to get the first result, the code should rather be:

 return (User) _sessionFactory.getCurrentSession().createQuery(hql)
    .setParameter("email", email)
    .uniqueResult();

Indeed you get this error because you try to cast a Query instance into a User which cannot be done, you need to execute the query first to get your User instance.

---

If you want to get several results then consider using list() , the code will then be something like:

 return (List<User>) _sessionFactory.getCurrentSession().createQuery(hql)
    .setParameter("email", email)
    .list();

Answer 2

It seems that you forgot to call the getResultList() method at the end.

return (List<User>) _sessionFactory.getCurrentSession().createQuery(hql)
              .setParameter("email", email)
              .getResultList();

You should notice that since you are expecting more than one result, you'll need to change this command a bit or adapt the code to where this is returning to.

Answer 3

You have to extract your result out of Query. You can extract a single Object by using

.createQuery(hql).getSingleResult();