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存在问题，其中连接列不是基类的主键，因为数据库结构落后。 以下是表格设计的示例：

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")
)

这里是映射（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;
}

这会失败并出现异常：

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

您不能两次映射双向关联。必须使用mappedBy 属性将单面标记为多面的反面：

@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;

没有理由告诉 Hibernate 两次关联是由连接列 FOOID 映射的。而且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

以上应该可以工作，但不是由于以下 Hibernate 错误：这是一个 Hibernate 错误。见HHH-4284。

为了规避这个问题，由于FOOID足以保证唯一性，解决方案是从所有者ID和@IdClass注释中删除@Id注释。

Answer 2

你可以这样做......它应该工作 -

@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(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    @JoinColumn(name = "FOOID",nullable=false)
    @ForeignKey(name = "fk")     
    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", updatable = false, insertable = false, nullable=false)  
     private Foo foo;
}

Answer 3

您在 FOO 表中使用了复合主键。因此，您应该尝试@EmbeddedId 属性，并且您应该需要 BAR 实体中与 FOO 实体连接的两列“OWNER_ID”和“FOO_ID”。