清除与JPA/JPQL的多人关系

Question

我有用户和角色。每个用户可以有许多角色。

我希望有一个批量操作，如删除所有用户角色，但保留用户和角色。那么，如何只截断manytomy表呢？

还有很长的路要走-

@Entity
@Table
public class Role {

    @Id
    @Column(name = "id", unique = true, nullable = false)
    private Long id;

    @ManyToMany(mappedBy = "roles")
    private Set<User> users = new HashSet<>();
}

@Entity
@Table
public class User {

    @Id
    @Column(name = "id", unique = true, nullable = false)
    private Long id;

    @ManyToMany(cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST})
    @JoinTable(
            name = "UserRole",
            joinColumns = {@JoinColumn(name = "id")},
            inverseJoinColumns = {@JoinColumn(name = "id")})
    private Set<Role> roles = new HashSet<>();
}

@Repository
public interface UsersRepository extends JpaRepository<User, Long> {

    @Modifying
    @Query("UPDATE User u SET u.roles = null")
    void clearAllRoleRelations();
}

我尝试了此操作，但得到了DML操作不支持的异常[更新users.entity.User u SET u.roles=null]

Answer 1

我让它工作了，但使用了一个本机查询，然后需要entityManager。如果要在同一事务中使用此选项，请清除。

    @Modifying
    @Query(nativeQuery = true, value = "DELETE FROM user_role")
    void clearAllRoleRelations();

  @Autowired
  private EntityManager entityManager;
    

  @Test
    public void clearAllRoleRelations() {

        //given
        Role roleIn = new Role();
        roleIn.setId(27L);

        User userIn = new User();
        userIn.Id(12L);

        //do
        roleIn = rolesRepository.save(roleIn);
        userIn = usersRepository.save(userIn);
        userIn.getRoles().add(roleIn);
        usersRepository.save(userIn);

        //verify
        usersRepository.clearAllRoleRelations();

        //important within the same transaction (native query)
        entityManager.clear();

        Optional<User> userOut = usersRepository.findById(userIn.getId());
        assertThat(userOut.isPresent()).isTrue();
        assertThat(userOut.get()).isEqualTo(userIn);
        assertThat(userOut.get().getRoles()).isEmpty();
    }

Answer 2

丢弃多个，并为联接表创建一个enity。这样，您就可以完全控制删除。