如何在非主键列上连接表？

Question

我在 ORM 类层次结构中的对象上的连接表上遇到问题，其中由于遗留数据库结构，连接列不是基类的主键。这是表格设计的示例：

CREATE TABLE "SCH"."FOO"
(
        "OWNERID"       NUMBER(10,0) NOT NULL ENABLE,
        "FOOID"         NUMBER(10,0) NOT NULL ENABLE,
        CONSTRAINT "FOO_PK" PRIMARY KEY ("OWNERID", "FOOID")
        CONSTRAINT "FOO_FK1" FOREIGN KEY ("OWNERID") REFERENCES "SCH"."OWNERS" ("OWNERID") ENABLE
)

CREATE TABLE "SCH"."BAR"
(
        "BARID"             NUMBER(10,0) NOT NULL ENABLE,
        "FOOID"             NUMBER(10,0)
        CONSTRAINT "BAR_PK" PRIMARY KEY ("BARID")
)

这是映射（删除了不必要的信息）

@Entity
@IdClass(FooId.class)
@Table(name = "FOO")
public class Foo implements java.io.Serializable
{
    @Id
    @Column(name = "OWNERID")
    private BigInteger ownerId;

    @Id
    @SequenceGenerator(name = "FOO_GENERATOR", sequenceName = "SEQ_FOO")
    @GeneratedValue(generator = "FOO_GENERATOR")
    @Column(name = "FOOID")
    private BigInteger id;

    @OneToMany(fetch = FetchType.LAZY)
    @JoinColumn(name = "FOOID", referencedColumnName = "FOOID")
    @Fetch(value = FetchMode.SUBSELECT)
    @Cascade(value = {CascadeType.ALL})
    private Set<Bar> bar = new LinkedHashSet<Bar>(0);
}


@Entity
@Table(name = "BAR")
public class Bar implements java.io.Serializable
{
    @Id
    @Column(name = "BARID")
    private BigInteger id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "FOOID", referencedColumnName = "FOOID")
    private Foo foo;
}

这会失败，但有一个例外：

Caused by: org.hibernate.AnnotationException: referencedColumnNames(FOOID) of com.package.Bar.foo referencing com.package.Foo not mapped to a single property
    at org.hibernate.cfg.BinderHelper.createSyntheticPropertyReference(BinderHelper.java:204)
    at org.hibernate.cfg.ToOneFkSecondPass.doSecondPass(ToOneFkSecondPass.java:114)
    at org.hibernate.cfg.Configuration.processEndOfQueue(Configuration.java:1580)
    at org.hibernate.cfg.Configuration.processFkSecondPassInOrder(Configuration.java:1503)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1419)
    at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1375)

您能帮忙解决一下吗？

Answer 1

您不得两次映射双向关联。必须使用以下属性将“一侧”标记为“多一侧”的反面mappedBy：

@OneToMany(fetch = FetchType.LAZY, mappedBy = "foo")
@Fetch(value = FetchMode.SUBSELECT)
@Cascade(value = {CascadeType.ALL})
private Set<Bar> bar = new LinkedHashSet<Bar>(0);

...

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "FOOID", referencedColumnName = "FOOID")
private Foo foo;

没有理由两次告诉 Hibernate 该关联是由连接列 FOOID 映射的。这样做实际上是一个错误，因为它定义了两个不同的单向关联而不是一个双向关联。

编辑

上面的内容应该可以工作，但由于以下 Hibernate bug 而不起作用：这是一个 Hibernate bug。参见HHH-4284。

为了避免这个问题，由于FOOID足以保证唯一性，解决方案是@Id从所有者 ID 和@IdClass注释中删除注释。