Hibernate @OneToMany 添加新实体时出现异常

Question

I have two entities in MySql Database. First is Users entity and second is Movies . I set relation @OneToMany and @ManyToOne . I mean, one user can own multiple movies and several movies can belong to one user.

@Data
@Entity
@Table(name = "movies", uniqueConstraints = {@UniqueConstraint(columnNames = {"user_id"})})
public class Movies {


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

    @Column(name = "movie_name", nullable = false)
    private String name;

    @Column(name = "expirationTime")
    private DateTime expirationTime;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "user_id", nullable = false)
    private Users userId;




@NoArgsConstructor
@AllArgsConstructor
@Data
@Entity
@Table(name = "user")
public class Users {
    

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

    @Column(name = "first_name")
    private String firstName;

    @Column(name = "last_name")
    private String lastName;

    @Column(name = "phone_number", nullable = true)
    private String phoneNumber;
    

    @Getter
    @Setter
    @OneToMany(mappedBy = "userId", cascade = CascadeType.ALL)
    @Builder.Default
    private Set<Movies> movies = new HashSet<>(0);

I could add one entity of Movies per User. When I want to add another row for this same user (adding new movie) I receive exception like this:

Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '7' for key 'movies.UKno13de9csa3gf2das1j6dsa12

Any suggestion how to solve this issue?

Answer 1

The issue was @UniqueConstraint. I had to restore DB before changes were applied in structure. Removing constraint in DB doesn't help. So as suggested I removed from code this annotation and let hibernate do the job. Now I can add multiple entities for single user.

Answer 2

Why are you passing zero to the set? I suspect, that zero is causing the issue here.

private Set<Movies> movies = new HashSet<>(0);

Remove the zero and it will work.

private Set<Movies> movies = new HashSet<>();

Answer 3

• Drop all the tables directly from database and let hibernate recreate the tables as your old constraint can still be there.

• Remove the uniqueConstraints = {@UniqueConstraint(columnNames = {"user_id"})

• It tries to enforce a movie record can only have one unique user row

Answer 4

Your definition of unique constraint is wrong. Having @UniqueConstraint(columnNames = {"user_id"})} means there can only be one movie row with user 7. You need to add new constraint and set it on columns id, user_id. Also drop old one.

ALTER TABLE movies
ADD CONSTRAINT movie_user_uq
UNIQUE (id, user_id);