Hibernate使用orphanRemoval触发约束违规

Question

我在使用JPA/Hibernate(3.5.3)设置时遇到问题,我有一个实体,一个"帐户"类,它有一个子实体列表,"联系"实例.我正在尝试将Account的实例添加/删除到Account的List <Contact>属性中.

将新实例添加到集合中并调用saveOrUpdate(account)可以保持一切可爱.如果我然后选择从列表中删除联系人并再次调用saveOrUpdate,则SQL Hibernate似乎会产生涉及将account_id列设置为null,这违反了数据库约束.

我究竟做错了什么？

下面的代码显然是一个简化的摘要,但我认为它涵盖了问题,因为我在不同的代码中看到相同的结果,这真的是这个简单.

SQL:

CREATE TABLE account ( INT account_id );
CREATE TABLE contact ( INT contact_id, INT account_id REFERENCES account (account_id) );

Java的:

@Entity
class Account {
  @Id
  @Column
  public Long id;

  @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
  @JoinColumn(name = "account_id")
  public List<Contact> contacts;
}

@Entity
class Contact {
  @Id
  @Column
  public Long id;

  @ManyToOne(optional = false)
  @JoinColumn(name = "account_id", nullable = false)
  public Account account;
}

Account account = new Account();
Contact contact = new Contact();

account.contacts.add(contact);
saveOrUpdate(account);

// some time later, like another servlet request....

account.contacts.remove(contact);
saveOrUpdate(account);

结果:

UPDATE contact SET account_id = null WHERE contact_id = ?

编辑#1:

可能这实际上是一个错误 http://opensource.atlassian.com/projects/hibernate/browse/HHH-5091

编辑#2:

我有一个似乎有效的解决方案,但涉及使用Hibernate API

class Account {
    @SuppressWarnings("deprecation")
    @OneToMany(cascade = CascadeType.ALL, mappedBy = "account")
    @Cascade(org.hibernate.annotations.CascadeType.DELETE_ORPHAN)
    @JoinColumn(name = "account_id", nullable = false)
    private Set<Contact> contacts = new HashSet<Contact>();
}

class Contact {
    @ManyToOne(optional = false)
    @JoinColumn(name = "account_id", nullable = false)
    private Account account;
}

由于不推荐使用Hibernate CascadeType.DELETE_ORPHAN,我不得不假设它已被JPA2版本取代,但实现缺乏某些功能.

Answer 1

一些评论:

• 由于您具有双向关联,因此需要添加mappedBy属性以声明关联的拥有方.
• 另外,请注意,在处理双向关联时,您需要管理链接的两端,我建议使用防御方法(如下所示).
• 你必须实施equals和hashCode开启Contact.

所以,在Account,修改映射,如下所示:

@Entity
public class Account {
    @Id @GeneratedValue
    public Long id;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "account", orphanRemoval = true)
    public List<Contact> contacts = new ArrayList<Contact>();

    public void addToContacts(Contact contact) {
        this.contacts.add(contact);
        contact.setAccount(this);
    }

    public void removeFromContacts(Contact contact) {
        this.contacts.remove(contact);
        contact.setAccount(null);
    }

    // getters, setters
}

在Contact,重要的部分是该@ManyToOne字段应该将optional标志设置为false:

@Entity
public class Contact {
    @Id @GeneratedValue
    public Long id;

    @ManyToOne(optional = false)
    public Account account;

    // getters, setters, equals, hashCode

}

通过这些修改,以下工作正常:

Account account = new Account();
Contact contact = new Contact();

account.addToContact(contact);
em.persist(account);
em.flush();

assertNotNull(account.getId());
assertNotNull(account.getContacts().get(0).getId());
assertEquals(1, account.getContacts().size());

account.removeFromContact(contact);
em.merge(account);
em.flush();
assertEquals(0, account.getContacts().size());

Contact正如预期的那样,孤儿被删除了.经过Hibernate 3.5.3-Final测试.