当实体映射为多对一时，热获取带有休眠的对象列表

Question

I have a class User , that contains List of Contacts User class:

@Entity
@Table(name = "profile")
public class User implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    @Column(unique = true)
    private String login;

    @OneToMany(mappedBy = "owner", cascade = CascadeType.ALL)
    private List<Contact> contacts;
    ...
    ...
}

Contact class:

@Entity
@Table
public class Contact implements Serializable {
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private int id;

        @ManyToOne
        @JoinColumn(name = "user_profile_id")
        private User owner;
        ...
        ...
    }

how may i get List of Contacts by User.id field?

Answer 1

Not sure I got what you want...

Simply look for the User by Id, and you will get his/her contacts. However, the collection will be lazy loaded, and the list will be really loaded when you will call getContacts() or Hibernate.initialize(user.getContacts()) . Change FetchMode as EAGER in the @OneToMany in case you don't want lazy loading...

For eg, using HQL Query :

String hql = "from User where id = :userid";
Query query = session.createQuery(hql);
query.setInteger("userid", myUserIdIWantContacts);
User user = (User) query.uniqueResult();

or Criteria :

Criteria cr = session.createCriteria(User.class);
cr.add(Restrictions.eq("id", myUserIdIWantContacts));
User user = (User) cr.uniqueResult();

Answer 2

Contact has a foreign key column associated to User so you don't need to use join

from Contact where owner.id = :userId

Please, don't use primitive types like int id , use Integer id instead.