Java JPA 未将外键保存到 @OneToMany 关系

JPA not saving foreign key to @OneToMany relation

提问by NA.

I'm using Spring with Hibernate as a JPA provider and are trying to get a @OneToMany (a contact having many phonenumbers) to save the foreign key in the phone numbers table. From my form i get a Contact object that have a list of Phone(numbers) in it. The Contact get persisted properly (Hibernate fetches an PK from the specified sequence). The list of Phone(numbers) also gets persisted with a correct PK, but there's no FK to the Contacts table.

我将 Spring 与 Hibernate 一起用作 JPA 提供程序，并尝试使用 @OneToMany（具有多个电话号码的联系人）将外键保存在电话号码表中。从我的表单中，我得到一个 Contact 对象，其中包含电话（号码）列表。Contact 得到正确的持久化（Hibernate 从指定的序列中获取一个 PK）。Phone(numbers) 列表也使用正确的 PK 持久化，但 Contacts 表没有 FK。

public class Contact implements Serializable {

    @OneToMany(mappedBy = "contactId", cascade = CascadeType.ALL, fetch=FetchType.EAGER)
    private List<Phone> phoneList;

}

public class Phone implements Serializable {

    @JoinColumn(name = "contact_id", referencedColumnName = "contact_id")
    @ManyToOne
    private Contact contactId;

}

@Repository("contactDao")
@Transactional(readOnly = true)
public class ContactDaoImpl implements ContactDao {

    @Transactional(readOnly = false, propagation = Propagation.REQUIRES_NEW)
    public void save(Contact c) {
        em.persist(c);
        em.flush();
    }
}


@Controller
public class ContactController {
    @RequestMapping(value = "/contact/new", method = RequestMethod.POST)
    public ModelAndView newContact(Contact c) {
        ModelAndView mv = new ModelAndView("contactForm");
        contactDao.save(c);
        mv.addObject("contact", c);
        return mv;
    }
}

Hopefully I got all of the relevant bits above, otherwise please let me know.

希望我得到了上面的所有相关信息，否则请告诉我。

采纳答案by cletus

You have to manage the Java relationships yourself. For this kind of thing you need something like:

您必须自己管理 Java 关系。对于这种事情，你需要这样的东西：

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

  @OneToMany(cascade = CascadeType.PERSIST, mappedBy = "contact")
  private List<Phone> phoneNumbers;

  public void addPhone(PhoneNumber phone) {
     if (phone != null) {
        if (phoneNumbers == null) {
            phoneNumbers = new ArrayList<Phone>();          
        }
        phoneNumbers.add(phone);
        phone.setContact(this);
     }
  }

  ...
}

@Entity
public class Phone {
  @Id
  private Long id;

  @ManyToOne
  private Contact contact;

  ...
}

回答by mR_fr0g

In reply to Cletus' answer. I would say that it's important to have the @columnannotation on the id fields, as well as all the sequence stuff. An alternative to using the mappedBy parameter of the @OneToManyannotation is to use the @JoinColumnannotation.

回复 Cletus 的回答。我会说@column在 id 字段以及所有序列内容上都有注释很重要。使用@OneToMany注释的mappedBy 参数的替代方法是使用@JoinColumn注释。

As a kinda aside your implementation of addPhone needs looking at. It should probably be something like.

顺便说一下，您需要查看 addPhone 的实现。它应该是类似的。

public void addPhone(PhoneNumber phone) {
    if (phone == null) {
        return;
    } else {
        if (phoneNumbers == null) {
            phoneNumbers = new ArrayList<Phone>();
        }
        phoneNumbers.add(phone);
        phone.setContact(this);
    }
}

回答by Camel

I don't think the addPhonemethod is necessary, you only have to set the contact in the phone object:

我不认为addPhone方法是必要的，你只需要在电话对象中设置联系人：

phone.setContact(contact);

回答by samsong8610

If the Contact-Phone relationship is unidirectional, you can also replace mappedByin @OneToManyannotation with @JoinColumn(name = "contact_id").

如果 Contact-Phone 关系是单向的，您也可以mappedBy在@OneToMany注释中替换 为@JoinColumn(name = "contact_id")。

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

  @OneToMany(cascade = CascadeType.PERSIST)
  @JoinColumn(name = "contact_id")
  private List<Phone> phoneNumbers;

  // normal getter/setter
  ...
}

@Entity
public class PhoneNumber {
  @Id
  private Long id;

  ...
}

Similar in JPA @OneToMany -> Parent - Child Reference (Foreign Key)

在JPA @OneToMany -> Parent - Child Reference (Foreign Key) 中类似

回答by Tom Chamberlain

If you want your relationship unidirectional i.e. can navigate from Contact to Phone's only, you need to add

如果您希望您的关系单向，即只能从联系人导航到电话，则需要添加

@JoinColumn(name = "contact_id", nullable = false)

Under your @OneToManyon your parent entity.

在您@OneToMany的父实体之下。

nullable = falseIS VITALif you want hibernate to populate the fk on the child table

nullable = false是至关重要的，如果你想Hibernate来填充子表上的FK

回答by Ilya Lysenko

Try this sample:

试试这个示例：

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

    @JoinColumn(name = "contactId")
    @OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
    private Set<Phone> phones;
}

@Entity
public class Phone {
    @Id
    private Long id;
    private Long contactId;
}