java - 多对多关系未保存

Question

我有一个用户和一个电影模型。在我的应用程序中，用户可以将电影对象保存到数据库中。我想在用户和他们添加的电影之间建立一种关系。

我从 Angular 前端获取一个电影对象:

@RequestMapping(value = "/", method = RequestMethod.POST)
public Movie createMovie(@RequestBody Movie movie){
    return movieService.createMovie(movie);
}

这将调用服务和 createMovie 函数:

@Override 
public Movie createMovie(Movie movie) {
    return movieRepository.save(movie);
}

电影对象现已添加到数据库中的电影表中，但我的 movie_user 表中未添加任何内容。

在我的 User.java 中我有:

@ManyToMany(mappedBy = "users")
private List<Movie> movies = new ArrayList<>();

在我的 Movie.java 中我有:

@ManyToMany(cascade = {
    CascadeType.PERSIST,
    CascadeType.MERGE
})

@JoinTable(name = "movie_user",
    joinColumns = @JoinColumn(name = "movie_id"),
    inverseJoinColumns = @JoinColumn(name = "user_id")
)

private List<User> users = new ArrayList<>();

在我的 MySQL 工作台中，我看到一个 movie_user 表，其中包含 2 列:movie_id 和 user_id。当我保存电影时，该表没有任何反应。

这是服务器的输出:

2017-11-07 20:35:04.491  INFO 8140 --- [nio-8090-exec-1] c.m.s.JwtAuthenticationTokenFilter       : checking authentication f├╝r user admin
2017-11-07 20:35:04.491  INFO 8140 --- [nio-8090-exec-1] o.h.h.i.QueryTranslatorFactoryInitiator  : HHH000397: Using ASTQueryTranslatorFactory
Hibernate: select user0_.id as id1_3_, user0_.email as email2_3_, user0_.enabled as enabled3_3_, user0_.firstname as firstnam4_3_, user0_.lastpasswordresetdate as las
tpass5_3_, user0_.lastname as lastname6_3_, user0_.password as password7_3_, user0_.username as username8_3_ from user user0_ where user0_.username=?
Hibernate: select authoritie0_.user_id as user_id1_4_0_, authoritie0_.authority_id as authorit2_4_0_, authority1_.id as id1_0_1_, authority1_.name as name2_0_1_ from
user_authority authoritie0_ inner join authority authority1_ on authoritie0_.authority_id=authority1_.id where authoritie0_.user_id=?
2017-11-07 20:35:04.514  INFO 8140 --- [nio-8090-exec-1] c.m.s.JwtAuthenticationTokenFilter       : authenticated user admin, setting security context
Hibernate: select movie0_.id as id1_1_1_, movie0_.name as name2_1_1_, users1_.movie_id as movie_id1_2_3_, user2_.id as user_id2_2_3_, user2_.id as id1_3_0_, user2_.em
ail as email2_3_0_, user2_.enabled as enabled3_3_0_, user2_.firstname as firstnam4_3_0_, user2_.lastpasswordresetdate as lastpass5_3_0_, user2_.lastname as lastname6_
3_0_, user2_.password as password7_3_0_, user2_.username as username8_3_0_ from movie movie0_ left outer join movie_user users1_ on movie0_.id=users1_.movie_id left o
uter join user user2_ on users1_.user_id=user2_.id where movie0_.id=?
Hibernate: select tbl.next_val from hibernate_sequences tbl where tbl.sequence_name=? for update
Hibernate: update hibernate_sequences set next_val=?  where next_val=? and sequence_name=?
Hibernate: insert into movie (name, id) values (?, ?)

所以看起来 hibernate 正在对表做一些事情，但我不确定现在应该做什么。 This is the tutorial that I followed .

Answer 1

教程说，

the add/remove utility methods are mandatory if you use bidirectional associations so that you can make sure that both sides of the association are in sync.

并且您需要教程中的方法 addTag 和 removeTag 之类的方法，因为 Hibernate 不会自动填充。例如

class User {

 public void addMovie(Movie movie) {
        movies.add(movie);
        movie.getUsers().add(this);
    }
}

所以只要多关注教程，一切都会起作用