JPA，Hibernate我可以做复合主键吗？哪一个元素是foreign kay@OneToMany？

Question

我希望在我的实体中有一个由两列(属性)组成的复合主键，同时有一列是外键。

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：

我对Brian Vosburgh进行了测试，效果良好：

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列是复合FK。我一直试图类似下面的解决方案，但无法理解如何编写ServicePointPhotoId @IdClass

Answer 1

制作复合主键的最佳方式是将@EmbeddedId与相应的< code > @ embedded 类一起使用。

在我们的400多个数据库实体中，大约有135个使用Embedded ID类来实现复合（多字段）主键。

SO上有很多问题和答案，并附有这些示例。

Answer 2

去掉< code>providerId字段及其对应的getter和setter。将< code>@Id批注添加到< code>getProvider()中。如下定义< code>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（即提供程序）中的属性名称匹配，但属性的类型不同。在IdClass中，属性类型必须与Provider的Id属性的类型匹配。

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）；但是IdClass属性的类型必须匹配引用的Entity的IdClass（即ServicePointId）。

我使用过字段批注，但您可以将这些批注转换为属性批注。

同样:JPA 2.1规范在2.4.1.3部分有一个这种关系的例子。