Spring没有使用ManyToMany关系

Question

我有一个用户和一个电影模特：用户：

@Entity(name = "User")
@Table(name = "USER")
public class User {

    @Id
    @Column(name = "ID")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "user_seq")
    @SequenceGenerator(name = "user_seq", sequenceName = "user_seq", allocationSize = 1)
    private Long id;

    @Column(name = "USERNAME", length = 50, unique = true)
    @NotNull
    @Size(min = 4, max = 50)
    private String username;

    @Column(name = "PASSWORD", length = 100)
    @NotNull
    @Size(min = 4, max = 100)
    private String password;

    @Column(name = "FIRSTNAME", length = 50)
    @NotNull
    @Size(min = 4, max = 50)
    private String firstname;

    @Column(name = "LASTNAME", length = 50)
    @NotNull
    @Size(min = 4, max = 50)
    private String lastname;

    @Column(name = "EMAIL", length = 50)
    @NotNull
    @Size(min = 4, max = 50)
    private String email;

    @Column(name = "ENABLED")
    @NotNull
    private Boolean enabled;

    @Column(name = "LASTPASSWORDRESETDATE")
    @Temporal(TemporalType.TIMESTAMP)
    @NotNull
    private Date lastPasswordResetDate;

    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(
            name = "USER_AUTHORITY",
            joinColumns = {@JoinColumn(name = "USER_ID", referencedColumnName = "ID")},
            inverseJoinColumns = {@JoinColumn(name = "AUTHORITY_ID", referencedColumnName = "ID")})
    private List<Authority> authorities;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getFirstname() {
        return firstname;
    }

    public void setFirstname(String firstname) {
        this.firstname = firstname;
    }

    public String getLastname() {
        return lastname;
    }

    public void setLastname(String lastname) {
        this.lastname = lastname;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Boolean getEnabled() {
        return enabled;
    }

    public void setEnabled(Boolean enabled) {
        this.enabled = enabled;
    }

    public List<Authority> getAuthorities() {
        return authorities;
    }

    public void setAuthorities(List<Authority> authorities) {
        this.authorities = authorities;
    }

    public Date getLastPasswordResetDate() {
        return lastPasswordResetDate;
    }

    public void setLastPasswordResetDate(Date lastPasswordResetDate) {
        this.lastPasswordResetDate = lastPasswordResetDate;
    }

    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "user_movie",
        joinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id"),
        inverseJoinColumns = @JoinColumn(name = "movie_id", referencedColumnName = "id")
    )
    private Set<Movie> movies;    

    public Set<Movie> getMovies() {
        return movies;
    }

    public void setMovies(Set<Movie> movies) {
        this.movies = movies;
    }


}

电影：

@Entity(name = "Movie")
@Table(name = "movie")
public class Movie {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    private String name;

    public Movie(){}

    public Movie(Integer id, String name ) {
        this.id = id;
        this.name = name;
    }

    @ManyToMany(mappedBy = "movies")
    private Set<User> users;    
    public Set<User> getUsers() {
        return users;
    }

    public void addUser(User user){
        System.out.println("ADD MOVIE: " + user);
        users.add(user);
        user.getMovies().add(this);
    }

    public void setUsers(Set<User> users) {
        this.users = users;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString(){
        return "id: " + id + "name: " + name;
    }

}

我在这些模型之间建立了多对多关系。 如果我是正确的话，将用户作为关系的所有者。

在我的MovieController.java中，我有：

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

这将调用MovieService.java：

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

这将调用MovieRepository.java：

@Repository
public interface MovieRepository extends CrudRepository<Movie, Serializable> {}

当我从前端调用post methode时，电影记录会保存在我的电影表中，但是在user_movie表中不会创建任何记录。 因为我在用户和电影之间建立了多对多关系，所以Hibernate不会隐式执行此操作吗？

Answer 1

您保存了影片，并且还为了让用户保存了影片，必须在影片中设置级联。 否则，您可以将级联保留在用户中并保存他。

您需要将级联放置到要调用的实体上，以进行级联。

Movie{
    @ManyToMany(mappedBy = "movies", cascade={CascadeType.ALL})
    private Set<User> users;    
    public Set<User> getUsers() {
        return users;
    }
}

User {
    @ManyToMany
    @JoinTable(name = "user_movie",
        joinColumns = @JoinColumn(name = "user_id", referencedColumnName = "id"),
        inverseJoinColumns = @JoinColumn(name = "movie_id", referencedColumnName = "id")
    )
    private Set<Movie> movies; 
}

保存之前，请不要忘记将用户添加到电影中，反之亦然。

与所有双向关系一样，在两个方向上保持关系都是对象模型和应用程序的责任。 JPA中没有魔术，如果在集合的一侧添加或删除，则还必须在另一侧添加或删除，请参见对象损坏。 从技术上讲，如果仅从关系的拥有方进行添加/删除，则数据库将正确更新，但是对象模型将不同步，这可能会引起问题。

参见此处： https : //en.wikibooks.org/wiki/Java_Persistence/ManyToMany

Answer 2

对于第一个视图，您的代码是正确的。
问题可能出在GenerationType.SEQUENCE中 （尝试使用GenerationType.AUTO作为用户的ID），或者您需要在控制器中添加@Transactional 。