CODEWITHSUNDEEP
javahibernate
Johnas
Johnas

Reputation: 326

Hibernate ERROR: Cannot delete or update a parent row: a foreign key constraint fails

I have the following classes:

@Entity
@Table(name = "lecture")
public class Lecture {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    @Column(nullable = false)
    private String name;
    @OneToOne
    @JoinColumn(nullable = false, name = "professorId")
    @JsonIgnore
    private Professor professor;
}

And:

@Entity
@IdClass(ListenTo.class)
@Table(name = "listen_to")
public class ListenTo implements Serializable {
    @Id
    @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.REMOVE)
    @JoinColumn(nullable = false, name = "lectureId")
    private Lecture lecture;
    @Id
    @ManyToOne(cascade = CascadeType.REMOVE)
    @JoinColumn(nullable = false, name = "studentId")
    private Student student;
}

And I want to delete a lecture through this function:

public void delete(Lecture lecture) {
        currentSession().delete(lecture);
    }

I created the table like this:

create table lecture (
    id bigint primary key not null auto_increment,
    name varchar(500) not null,
    professorId bigint not null,
    foreign key (professorId) references professorId (id)
);

create table listen_to (
    lectureId BIGINT not null references lecture(id),
    studentId BIGINT not null references student(id),
    primary key(lectureId,studentId)
);

However, I keep getting this error:

Causing: java.sql.SQLIntegrityConstraintViolationException: (conn=10) Cannot delete or update a parent row: a foreign key constraint fails (`myDBS`.`listen_to`, CONSTRAINT `listen_to_ibfk_1` FOREIGN KEY (`lectureId`) REFERENCES `lecture` (`id`))

I tried multiple things, including using this function to delete:

 public boolean deleteById(Class<?> type, Serializable id) {
        Object persistentInstance = currentSession().load(type, id);
        if (persistentInstance != null) {
            currentSession().delete(persistentInstance);
            return true;
        }
        return false;
    }

but it still doesn't work..

Upvotes: 0

Views: 557

Answers (1)

Christian Beikov
Christian Beikov

Reputation: 16400

You first have to delete all ListenTo entries that refer to this lecture before you can delete the lecture. Use delete from ListenTo l where l.lecture.id = :id and bind the lecture id, before you delete the lecture itself.

Upvotes: 1

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