Question

我有一个用户和一个电影模型：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的关系。如果我是正确的，那么用户就是关系的所有者。

在我的MovieController.java中，我有：

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

这会调用MovieService.java：

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

这会调用MovieRepository.java：

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

当我从前端调用post方法时，电影记录保存在我的影片表中，但是在user_movie表中没有创建记录。由于我在用户和电影之间建立了多对多的关系，Hibernate不会隐含这样做吗？

Answer 1

您保存电影，并且为了保存用户，必须在电影中设置级联。否则你可以在用户中保留级联并保存他。

您需要将级联放到您调用save的实体上以进行级联。

public interface repository  extends JpaRepository<User, Long> {
 List<User> findByUserId(String userId)
}

在保存之前，不要忘记将用户添加到电影，反之亦然。

与所有双向关系一样，对象模型和应用程序负责维护双向关系。 JPA中没有任何魔力，如果您在集合的一侧添加或删除，您还必须在另一侧添加或删除，请参阅对象损坏。从技术上讲，如果您只是从关系的拥有方添加/删除数据库，那么数据库将会正确更新，但随后您的对象模型将不同步，这可能会导致问题。

见这里：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在 GenerationType.SEQUENCE （尝试将GenerationType.AUTO用于用户的ID），或者您需要将 @Transactional 添加到您的控制器。

Spring没有使用ManyToMany关系

2 个答案: