Hibernate：从另一个表映射字段

Question

我有三个表A表有字段

id

带字段的表B

id

带字段的表C

id_a
id_b

id_a和id_b分别引用表A的id和表B的id。表C的postgres定义如下：

CREATE TABLE C (
    id_a BIGINT          NOT NULL REFERENCES a(id) ON UPDATE CASCADE ON DELETE CASCADE,
    id_b BIGINT          NOT NULL REFERENCES b(id) ON UPDATE CASCADE ON DELETE CASCADE,
    CONSTRAINT c_pkey
        PRIMARY KEY (a, b)
);

然而，在我的代码中，我不需要表C的实体。所以我希望能够在@ManyToOne关系中映射实体A和B：

@Entity
public class A {
    private Long id;

    @ManyToOne
    @JoinTable(name = "C",
        joinColumns = @JoinColumn(name = "id_a", referencedColumnName = "id"),
        inverseJoinColumns = @JoinColumn(name = "id_a", referencedColumnName = "id"))
    private B b;
}

@Entity
public class B {
    private Long id;
}

我有一个测试是这样的：

    @Test
    void shouldFindBForA() {
        //given
        var a = new A();
        var b = new B();

        aRepository.saveAndFlush(a);
        bRepository.saveAndFlush(b);
        //when
        A foundA = aRepository.findAll().get(0);
        //then
        assertThat(foundA.getB()).isNotNull();
    }

在isNotNull断言中失败。

我做错了什么？

Answer 1

两个@JoinColumn都指向同一个id“id_a”