使用 orphanRemoval 触发 Hibernate 违反约束 [英] Hibernate triggering constraint violations using orphanRemoval

问题描述

我在使用 JPA/Hibernate (3.5.3) 设置时遇到问题，我在其中有一个实体，即帐户"类，其中包含子实体列表和联系人"实例.我正在尝试能够将 Contact 的实例添加/删除到 List<Contact>帐户的财产.

I'm having trouble with a JPA/Hibernate (3.5.3) setup, where I have an entity, an "Account" class, which has a list of child entities, "Contact" instances. I'm trying to be able to add/remove instances of Contact into a List<Contact> property of Account.

将一个新实例添加到集合中并调用 saveOrUpdate(account) 可以保留所有可爱的东西.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 似乎产生涉及将 account_id 列设置为 null，这违反了数据库约束.

Adding a new instance into the set and calling saveOrUpdate(account) persists everything lovely. If I then choose to remove the contact from the list and again call saveOrUpdate, the SQL Hibernate seems to produce involves setting the account_id column to null, which violates a database constraint.

我做错了什么?

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，这真的很简单.

The code below is clearly a simplified abstract but I think it covers the problem as I'm seeing the same results in different code, which really is about this simple.

SQL:

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

Java:

@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:

这可能是一个错误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

I've got a solution that seems to work, but involves using the 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 Hibernate CascadeType.DELETE_ORPHAN 已被弃用，我不得不假设它已被 JPA2 版本取代，但实现中缺少一些东西.

Since Hibernate CascadeType.DELETE_ORPHAN is deprecated, I'm having to assume that it has been superseded by the JPA2 version, but the implementation is lacking something.

推荐答案

备注:

• 因为你有一个双向关联，你需要添加一个mappedBy属性来声明关联的拥有方.
• 另外不要忘记在使用双向关联时需要管理链接的两端，我建议为此使用防御方法(如下所示).
• 并且您必须在 Contact 上实现 equals 和 hashCode.

• Since you have a bi-directional association, you need to add a mappedBy attribute to declare the owning side of the association.
• Also don't forget that you need to manage both sides of the link when working with bi-directional associations and I suggest to use defensive methods for this (shown below).
• And you must implement equals and hashCode on Contact.

所以，在Account中，修改映射如下:

So, in Account, modify the mapping like this:

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

In Contact, the important part is that the @ManyToOne field should have the optional flag set to false:

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

    @ManyToOne(optional = false)
    public Account account;

    // getters, setters, equals, hashCode

}

经过这些修改后，以下内容才有效:

With these modifications, the following just works:

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());

和预期的一样，孤立的 Contact 被删除了.使用 Hibernate 3.5.3-Final 测试.

And the orphaned Contact gets deleted, as expected. Tested with Hibernate 3.5.3-Final.

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