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我在创建父对象和子对象并使用 JPA 和休眠将它们一次性保存到数据库时遇到问题。父类如下所示：

@Entity
@Table(name = "PUser")
public final class User {

    @Id
    @Column(name = "ID", unique = true, nullable = false, updatable = false)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private long id;

}

子对象使用复合键，其中一个字段是父对象的 ID：

@Entity
@Table(name = "PAttribute")
public final class Attribute {

   @EmbeddedId
    @AttributeOverrides({
                    @AttributeOverride(name = "domain", column = @Column(name = "domain", nullable = false, length = 128)),
                    @AttributeOverride(name = "name", column = @Column(name = "name", nullable = false, length = 128)),
                    @AttributeOverride(name = "userid", column = @Column(name = "userid", nullable = false)) })
    private AttributePk pk;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "userid", nullable = false, insertable = false, updatable = false)
    private User user;

}

复合键类是：

    @Embeddable
    public class AttributePk implements java.io.Serializable {

            private static final long serialVersionUID = -7003721226789641149L;

            @Column(nullable = false, length = 128)
            private String domain;

            @Column(nullable = false, length = 128)
            private String name;

            @Column(nullable = false)
            private long userid;

    }

现在当我创建一个新用户并添加一个附件，然后尝试保存对象图

    User user = new User("joe1.bloggs@ft.com", "xyz");
    user.setScreenName("joe1bloggs");
    user.addAttribute("domain", "name", 212);

    target.saveAndFlush(user);

我得到了例外

    Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`fta_portal_user/PAttribute`, CONSTRAINT `userId` FOREIGN KEY (`userid`) REFERENCES `PUser` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:513)

显然 Attribute 子对象没有设置用户对象的 ID。

我知道我可以执行以下操作，但很奇怪，我不能只创建一个对象层次结构，而 Hibernate 会计算出如何相应地设置 ID。我怀疑没有办法解决这个问题，因为 saveAndFlush() 返回一个新实例，而不仅仅是更新输入参数版本。

    User user = new User("joe1.bloggs@ft.com", "xyz");
    user.setScreenName("joe1bloggs");

    // target is an JpaRepository intergafe
    user = target.saveAndFlush(user);

    user.addAttribute("domain", "name", 212);

    target.saveAndFlush(user);

任何人都有任何想法，或者这只是一个与之共存的案例？

谢谢

缺口

编辑：您可以通过将 @MapsId 注释添加到子类来使其工作（感谢 axtavt 的回复）。IE

    @MapsId("userId")
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "userId", nullable = false, insertable = false, updatable = false)
    private User user;
4

1 回答 1

1

您是否尝试将其映射如下：

@ManyToOne(fetch = FetchType.LAZY)     
@MapsId("userid")
private User user;

据我了解，在这种情况下userid，字段AttributePk应该自动填充 id user。

于 2012-09-12T11:54:51.873 回答