Question

I’m facing a problem while deleting a record that is referenced by another table.

This is a code example (simplest scenario):

@Entity
@Table(name = "user")
public class User
{
    @Id
    @GeneratedValue(generator="user_id_seq", strategy = GenerationType.SEQUENCE)
    @SequenceGenerator(name="user_id_seq", sequenceName="user_id_seq")
    @Column(name = "id", nullable = false)
    private int id;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "user")
    private Set<UserLog> userLogSet;

    // Other attributes
    // Getters/setters
}

---

@Entity
@Table(name = "user_log")
public class UserLog
{
    @Id
    @GeneratedValue(generator="user_log_id_seq", strategy = GenerationType.SEQUENCE)
    @SequenceGenerator(name="user_log_id_seq", sequenceName="user_log_id_seq")
    @Column(name = "id", nullable = false)
    private int id;

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

    // Other attributes
    // Getters/setters
}

Whenever I try to delete a record from the “user” table, I get the following error from postgreSQL:

ERROR: update or delete on table “user” violates foreign key
constraint “fk228a019fd2495d20” on table “user_log”
Detail: Key
(id)=(5) is still referenced from table “user_log”.

What am I doing wrong?

Thank you!

Update: I tried coding a small example, it can be found here. After launching the application with Tomcat the database schema is automatically created (check the connection details in /src/main/webapp/WEB-INF/jdbc.properties). When you visit http://localhost:8080 some data is inserted in the database. If I try to delete any teacher who is referenced in the student table (using phpPgAdmin), I get an error similar to the one above.

Answer 1

Your mapping seems to be wrong.

User can have many UserLogs I guess.

Also @OneToMany should be on a collection e.g. java.util.Set.
The cascade you have put is in UserLog which will take place if you act on instance of UserLog and not User.

As far as I understand change mapping as follows.

@Entity
@Table(name = "user")
public class User
{
    @Id
    @GeneratedValue(generator="user_id_seq", strategy = GenerationType.SEQUENCE)
    @SequenceGenerator(name="user_id_seq", sequenceName="user_id_seq")
    @Column(name = "id", nullable = false)
    private int id;

    @OneToMany(cascade = CascadeType.ALL,mappedBy="user")
    private Set<UserLog> userLogs;

    // Other attributes
    // Getters/setters
}


@Entity
@Table(name = "user_log")
public class UserLog
{
    @Id
    @GeneratedValue(generator="user_log_id_seq", strategy = GenerationType.SEQUENCE)
    @SequenceGenerator(name="user_log_id_seq", sequenceName="user_log_id_seq")
    @Column(name = "id", nullable = false)
    private int id;

    @ManyToOne
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    // Other attributes
    // Getters/setters
}

I guess you want to delete User and all its UserLog simply deleting User and leaving UserLogs doesn’t make sense.

Hope this helps.

Update:

Cascades as annotated in entity classes are managed by ORM, not if you
externally try to delete them from external tools like phpPgAdmin.