hibernate - JPA，Hibernate 我可以做复合主键，其中一个元素是外键@OneToMany？

Question

我想在我的实体中包含由 2 列(属性)组成的复合主键，并且其中一列同时作为外键。

我写了这样的东西，但不知道它是否有效，因为外键在 IntelliJ 数据源中被标记为生成的值

@Entity
@Table(name = "service_point")
@Access(AccessType.PROPERTY)
@IdClass(ServicePointId.class)
public class ServicePoint {

    private Long providerId;
    private Integer servicePointNumber;

    private Provider provider;

    @Id
    @Basic(optional = false)
    @Column(name = "provider_id", nullable = false, insertable = false,
            updatable = false, columnDefinition = "BIGINT UNSIGNED")
    public Long getProviderId() {
        return providerId;
    }

    public void setProviderId(Long providerId) {
        this.providerId = providerId;
    }

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "service_point_no", nullable = false, columnDefinition = "BIGINT UNSIGNED")
    public Integer getServicePointNumber() {
        return servicePointNumber;
    }

    public void setServicePointNumber(Integer servicePointNumber) {
        this.servicePointNumber = servicePointNumber;
    }

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "provider_id")
    public Provider getProvider() {
        return provider;
    }

    public void setProvider(Provider provider) {
        this.provider = provider;
    }
}

更新:

我测试了 Brian Vosburgh，它有效:

transaction.begin();

em.persist(provider);

ServicePoint servicePoint = new ServicePoint(provider, 1);

em.persist(servicePoint);

transaction.commit();

ServicePoint servicePoint2 = em.find(ServicePoint.class,
        new ServicePointId(provider.getUserId(), servicePoint.getServicePointNumber()));

assertTrue("Service point provider id and Provider provider id should be the same.",
        servicePoint2.getProvider().getUserId() == provider.getUserId());
assertNotNull("Service point number can not be null", servicePoint2.getServicePointNumber());
assertEquals(servicePoint2.getProvider(), provider);

transaction.begin();
em.remove(servicePoint);
em.remove(provider);
transaction.commit();

更新 2 - 下一个关系复合 PK(3 列)中的新问题，其中 2 个是复合 FK我一直在尝试类似于下面的解决方案，但无法通过 ServicePointPhotoId @IdClass 怎么写

Answer 1

去掉 providerId 字段及其对应的 getter 和 setter。向 getProvider() 添加一个 @Id 注释。像这样定义 IdClass:

public class ServicePointId {
    private Long provider;
    private Integer servicePointNumber;
    public Integer getProvider() {
        return provider;
    }
    public void setProvider(Integer provider) {
        this.provider = provider;
    }
    public Integer getServicePointNumber() {
        return servicePointNumber;
    }
    public void setServicePointNumber(Integer servicePointNumber) {
        this.servicePointNumber = servicePointNumber;
    }
}

请注意，IdClass 中的属性名称与 Entity(即 provider)中的属性名称匹配，但属性的类型是不同的。在 IdClass 中，属性类型必须与 Provider 的 Id 属性类型匹配。

这在 JPA 2.1 规范的第 2.4.1 节中进行了讨论。

更新 2 的建议:

public class ServicePointPhotoId {
    public ServicePointId servicePoint;
    public Long photoId;
}

@Entity
@IdClass(ServicePointPhotoId.class)
@Table(name="service_point_photo")
public class ServicePointPhoto {
    @Id
    @ManyToOne
    @JoinColumns({
        @JoinColumn(name="provider_id", referencedColumnName="provider_id"),
        @JoinColumn(name="service_point_no", referencedColumnName="service_point_no")
    })
    private ServicePoint servicePoint;

    @Id
    @Column(name="photo_id")
    private Long photoId;
}

注意属性名称必须匹配(即servicePoint)；但 IdClass 属性的类型必须与引用的 Entity 的 IdClass(即 ServicePointId)相匹配。

我使用了字段注释，但您可以将它们转换为属性注释。

同样:JPA 2.1 规范在第 2.4.1.3 节中有一个这种关系的示例。