Question

我有两个实体，用户和电影。它们是许多双向关系。我的问题是，当我通过控制器删除电影时，它也会同时删除与该电影实体相关的所有内容。我的用户以及该用户角色和电影实体。我该怎么做，以便在删除影片实体时将其从表中删除，并使用户保持其角色，而不是全部删除。

@Data
@ToString
@EqualsAndHashCode
@Entity
@Table(name = "movies")
public class Movie {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name = "title")
    private String title;
    @Column(name = "description")
    private String description;
    @Column(name = "release_date")
    @Temporal(TemporalType.DATE)
    private Date release_date;
    @Column(name = "country")
    private String country;
    @Column(name = "category")
    private String category;
    @ManyToMany(mappedBy = "movies")
    @ToString.Exclude
    @EqualsAndHashCode.Exclude
    private Set<User> users = new HashSet<>();


@Data
@ToString
@Entity
@Table(name = "users")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Column(name = "username")
    private String username;
    @Column(name = "password")
    private String password;
    @Transient
    private String confirmPassword;
    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "users_roles", joinColumns = {@JoinColumn(name = "user_id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name = "role_id", referencedColumnName = "id")})
    @ToString.Exclude
    @EqualsAndHashCode.Exclude
    private Set<Role> roles = new HashSet<>();

    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "users_movies", joinColumns = {@JoinColumn(name = "user_id", referencedColumnName = "id")},
            inverseJoinColumns = {@JoinColumn(name = "movie_id", referencedColumnName = "id")})
    @ToString.Exclude
    @EqualsAndHashCode.Exclude
    private Set<Movie> movies = new HashSet<>();

Answer 1

这是使用CascadeType.ALL时的预期行为，该行为隐式包括CascadeType.REMOVE-在删除拥有实体时会删除所有相关实体。

由于您在关联的两端都使用CascadeType.ALL，因此最终删除的记录超出了您的实际意图。

为避免这种情况：

您需要删除CascadeType.ALL或将其更改为类似MERGE / PERSIST的内容
自行处理实体的删除。
考虑使用批处理删除选项来指定关联的实体ID。

Answer 2

问题解决了，而不是使用mappingBy，我还向Movie实体添加了JoinTable批注，现在它可以正常工作了。

Answer 3

好吧，我不得不猜测您的Role实体是什么样子，因此请包括完整的示例。您没有指定是使用Spring-Data-Jpa还是仅使用Jpa，所以谁知道呢。编辑：在您的示例中，您最终澄清了您正在使用spring-data-jpa，但是概念仍然与此处相同。

@Data
@ToString
@Entity
@Table(name = "roles")
public class Role {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToMany(mappedBy="roles")
    @ToString.Exclude
    @EqualsAndHashCode.Exclude
    private Set<User> users = new HashSet<>();

}

并使用

tx.begin();

User u1 = new User();
Role r1 = new Role();
u1.setRoles(Collections.singleton(r1));
Movie m1 = new Movie();
m1.setDescription("movie 1");
Movie m2 = new Movie();
m2.setDescription("movie 2");
u1.setMovies(Stream.of(m1, m2).collect(Collectors.toSet()));
em.persist(u1);

tx.commit();

// now to query
em.clear();

tx.begin();
User u = em.createQuery("from User u left outer join fetch u.movies where u.id = 1", User.class).getSingleResult();
Movie m = u.getMovies().stream().filter(mv->mv.getDescription().equals("movie 1")).findFirst().get();
u.getMovies().remove(m);
em.remove(m);
tx.commit();

这将创建日志

create table users (id bigint generated by default as identity (start with 1), password varchar(255), username varchar(255), primary key (id))
create table users_movies (user_id bigint not null, movie_id bigint not null, primary key (user_id, movie_id))
create table users_roles (user_id bigint not null, role_id bigint not null, primary key (user_id, role_id))
alter table users_movies add constraint FKt4hasm7tvj0vor58ql33xptjy foreign key (movie_id) references movies
alter table users_movies add constraint FKhhj9vi206o88q0typfntk3fek foreign key (user_id) references users
alter table users_roles add constraint FKj6m8fwv7oqv74fcehir1a9ffy foreign key (role_id) references roles
alter table users_roles add constraint FK2o0jvgh89lemvvo17cbqvdxaa foreign key (user_id) references users
insert into users (id, password, username) values (default, ?, ?)
insert into movies (id, category, country, description, release_date, title) values (default, ?, ?, ?, ?, ?)
insert into movies (id, category, country, description, release_date, title) values (default, ?, ?, ?, ?, ?)
insert into roles (id) values (default)
insert into users_movies (user_id, movie_id) values (?, ?)
insert into users_movies (user_id, movie_id) values (?, ?)
insert into users_roles (user_id, role_id) values (?, ?)
select user0_.id as id1_2_0_, movie2_.id as id1_0_1_, user0_.password as password2_2_0_, user0_.username as username3_2_0_, movie2_.category as category2_0_1_, movie2_.country as country3_0_1_, movie2_.description as descript4_0_1_, movie2_.release_date as release_5_0_1_, movie2_.title as title6_0_1_, movies1_.user_id as user_id1_3_0__, movies1_.movie_id as movie_id2_3_0__ from users user0_ left outer join users_movies movies1_ on user0_.id=movies1_.user_id left outer join movies movie2_ on movies1_.movie_id=movie2_.id where user0_.id=1
delete from users_movies where user_id=? and movie_id=?
delete from movies where id=?

ManyToMany关系删除所有实体

3 个答案: