外键映射到 Embeddable 类

Question

我正在使用Hibernate 将 Entity1 连接到 Entity2，其中 Entity2 有一个复合主键。

Entity2 包含 2 列 id 和 type

public class Entity2 {
  @EmbeddedId
  private Entity2PK id;
}

@Embeddable
public class Entity2PK implements Serializable {
  @Column(name = "id")
  private String id;

  @Column(name = "type")
  private String type;
}

Entity1 包含 2 列 id 和 entity_2_id（外键参考 Entity2）

public class Entity1 {
  @Id
  @Column(name = "id", updatable = false, nullable = false)
  private String id;

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name="entity_2_id")
  private Entity2 entity2;
}

因此所有调用都失败了。有人对此有解决方案吗？

错误信息：

org.hibernate.AnnotationException: A Foreign key refering Entity2 from Entity1 has the wrong number of column. should be 4
    at org.hibernate.cfg.annotations.TableBinder.bindFk(TableBinder.java:646)
    at org.hibernate.cfg.ToOneFkSecondPass.doSecondPass(ToOneFkSecondPass.java:102)
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processEndOfQueue(InFlightMetadataCollectorImpl.java:1814)
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processFkSecondPassesInOrder(InFlightMetadataCollectorImpl.java:1758)
    at org.hibernate.boot.internal.InFlightMetadataCollectorImpl.processSecondPasses(InFlightMetadataCollectorImpl.java:1646)
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:286)
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:83)
    at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:473)
    at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:84)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:689)

Answer 1

你似乎和这个用户有同样的问题：AnnotationException: A Foreign key refering has the wrong number of column. should be 2

Entity1 不能将关系存储在单个列中，因为 Entity2 的 id 包含 2 列。您可以使用JoinColumns 而不是JoinColumn 来解决此问题。

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumns({
  @JoinColumn(name = "entity2_id", insertable = false, updatable = false),
  @JoinColumn(name = "entity2_type", insertable = false, updatable = false)
})
private Entity2 entity2;