如何在 JPA 中从 @EmbeddedId 设置反向引用

有人知道是否可以在 JPA 内建立反向引用@EmbeddedId.

例如，有一个形式的实体

@Entity
public class Entity1 {
    @Id
    @GeneratedValue
    private String identifier;

    private Entity1 relationToEntity1;
    //Left out the getters and setters for simplicity
}

还有一个具有复杂嵌入 ID 的第二个实体。第二个实体的一部分是对其父实体的引用。就像这样：

@Entity
public class Entity2 {
    @EmbeddedId private Entity2Identifier id;
    //Left out the getters and setters for simplicity.
}

@Embedabble
public class Entity2Identifier {
    private String firstPartOfIdentifier;
    private Entity1 parent;
    //Left out the getters and setters for simplicity.
}

当我尝试通过 JPA（实现是 EclipseLink）将这样的构造保存到数据库时，我收到以下形式的几个异常：

Exception [EclipseLink-93] (Eclipse Persistence Services - 1.1.0.r3639-SNAPSHOT): 
org.eclipse.persistence.exceptions.DescriptorException
Exception Description: The table [ENTITY1] is not present in this descriptor.
Descriptor: RelationalDescriptor(test.Entity2 --> [DatabaseTable(ENTITY2)])

您正在寻找的是派生 ID。如果您使用 JPA 2.0，则以下内容将起作用。您确实不希望整个父级成为 PK 的一部分，而只是父级 PK 的一部分。

@Entity
public class Entity1 {
    @EmbeddedId
    private ParentId identifier;

    @OneToOne(mappedBy="relationToEntity1")
    private Entity2 relationToEntity2;

    //Left out the getters and setters for simplicity
}

@Entity
public class Entity2 {
    @EmbeddedId private Entity2Identifier id;
    //Left out the getters and setters for simplicity.

    @MapsId("parentId")
    @OneToOne
    private Entity1 parent;

}

@Embedabble
public class Entity2Identifier {
    private String firstPartOfIdentifier;
    private ParentId parentId;
    //Left out the getters and setters for simplicity.
}