如何在多對多關系中使用hibernate和JPA刪除孤立實體？

Question

我想在多對多關系中使用hibernate和JPA刪除孤立實體，但我發現的所有屬性都是屬性。 org.hibernate.annotations.CascadeType.DELETE_ORPHAN（即@Cascade（value = {org.hibernate.annotations.CascadeType.DELETE_ORPHAN）），僅適用於一對多關系。

我想知道我是否可以在多對多關系中刪除孤兒。

Answer 1

從“Pro JPA 2”一書中：

只有在源端具有單基數的關系才能啟用孤立刪除，這就是為@OneToOne和@OneToMany關系注釋定義orphanRemoval選項的原因，但是@ManyToOne或@ManyToMany注釋都沒有。

這是一個無賴，但ManyToMany沒有JPA自動孤兒刪除。

Answer 2

實際上，我使用以下實體進行了測試：

@Entity
public class Person {
    @Id
    @GeneratedValue
    private Long id;
    private String firstName;
    private String lastName;

    @ManyToMany
    @Cascade(value = org.hibernate.annotations.CascadeType.DELETE_ORPHAN)
    private Set<Role> roles = new HashSet<Role>();

    //...
}

@Entity
public class Role {
    @Id
    @GeneratedValue
    private Long id;

    private String name;

    @ManyToMany(mappedBy = "roles")
    private Set<Person> persons = new HashSet<Person>();

    //...
}

並使用以下數據集：

<dataset>
    <PERSON id="1" firstname="john" lastname="doe"/>
    <PERSON id="2" firstname="clark" lastname="kent"/>
    <PERSON id="3" firstname="james" lastname="bond"/>
    <ROLE id="1" name="foo"/>
    <ROLE id="2" name="bar"/>
    <ROLE id="3" name="boo"/>
    <ROLE id="4" name="baz"/>
    <PERSON_ROLE persons_id="1" roles_id="1"/>
    <PERSON_ROLE persons_id="1" roles_id="2"/>
    <PERSON_ROLE persons_id="2" roles_id="2"/>
    <PERSON_ROLE persons_id="2" roles_id="3"/>
    <PERSON_ROLE persons_id="3" roles_id="1"/>
    <PERSON_ROLE persons_id="3" roles_id="4"/>
</dataset>

以下測試方法：

@Test
public void testCascadeDeleteOrphanOnDelete() {
    Person person = entityManager.find(Person.class, 1L);
    entityManager.remove(person);
    ReflectionAssert.assertPropertyLenientEquals("id", Arrays.asList(2, 3), findAllPersons());
    ReflectionAssert.assertPropertyLenientEquals("id", Arrays.asList(3, 4), findAllRoles());

}

private List<Person> findAllPersons() {
    return entityManager.createQuery("from Person").getResultList();
}

private List<Role> findAllRoles() {
    return entityManager.createQuery("from Role").getResultList();
}

剛過去。 低於產生的輸出：

Hibernate: select personx0_.id as id17_0_, personx0_.firstName as firstName17_0_, personx0_.lastName as lastName17_0_ from Person personx0_ where personx0_.id=?
Hibernate: select roles0_.persons_id as persons1_1_, roles0_.roles_id as roles2_1_, rolex1_.id as id18_0_, rolex1_.name as name18_0_ from Person_Role roles0_ left outer join Role rolex1_ on roles0_.roles_id=rolex1_.id where roles0_.persons_id=?
Hibernate: delete from Person_Role where persons_id=?
Hibernate: delete from Role where id=?
Hibernate: delete from Role where id=?
Hibernate: delete from Person where id=?
Hibernate: select personx0_.id as id17_, personx0_.firstName as firstName17_, personx0_.lastName as lastName17_ from Person personx0_
Hibernate: select rolex0_.id as id18_, rolex0_.name as name18_ from Role rolex0_

Answer 3

到目前為止，ManyToMany注釋沒有orphanRemoval屬性。 我也有同樣的問題。 並且在數據庫上實現它的建議無法解決問題。 JPA的整個哲學是反對在數據庫上實現邏輯，而是通過映射。

Answer 4

試試這個：

@ManyToMany(cascade = CascadeType.ALL, orphanRemoval=true, fetch = FetchType.LAZY, mappedBy = "yourObject")