Persistence Exception foreign key contraint fails in hibernate

Question

I have defined the following two classes in hibernate

@Entity
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String name;
 
}

@Entity
public class PhoneNumber {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @ManyToOne(cascade = CascadeType.ALL)
    private Person person;
 
}

When I persist a phone number object or a person object it's getting inserted properly. But when I do

 Person person = session.get(Person.class,1);
        session.remove(person);
        transaction.commit();

I get the foreign key violation exception. But since I have declared a column as ManyToOne shouldn't hibernate automatically delete the corresponding phonnumber records?
I am not sure if I need to add any extra code to do that

Renis1235 · Accepted Answer · 2022-02-25T10:44:05.283

0

You have a bi-directional relationship, that is why you have to add the PhoneNumbers in your Person too. And use the mappedBy attribute to show that the Person is the inverse side and whenever it is deleted, please delete every phone number also.

Like this:

@Entity
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String name;

    @OneToMany(mappedBy="person", cascade = CascadeType.ALL)
    private Set<PhoneNumber> phoneNumbers;
 
}

Check this for more information.

edited Feb 25 '22 at 10:44

answered Feb 25 '22 at 10:30

Renis1235

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Its still throwing the same error – dnaiel Feb 25 '22 at 10:31
It worked when I added the cascadeType=ALL – dnaiel Feb 25 '22 at 10:39
I intentionally left that information out of the answer for you to figure it out yourself :). Glad it worked. – Renis1235 Feb 25 '22 at 10:40
What's the purpose of JoinColumn annotation, then? I don't see any use in this example. Could we use it for some purpose here? – dnaiel Feb 25 '22 at 10:54
Set the `JoinColumn` in the `Person` field of the `PhoneNumber` class to specify how will the `Person` be referenced in this table. – Renis1235 Feb 25 '22 at 11:02

score 0 · Answer 2 · answered Feb 25 '22 at 10:38

First of all, you have to define the relationship between Person and PhoneNumber in both classes.

The error is thrown because there are phone numbers depending on the person object you removed. If you add @OneToMany you can define also the property cascade = CascadeType.ALL and then all phone numbers are removed consequently.

@Entity
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    private String name;

    @OneToMany(mappedBy = "person", cascade = CascadeType.ALL)
    private List<PhoneNumber> phoneNumbers;
}

@Entity
public class PhoneNumber {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

    @ManyToOne
    private Person person;

}

Persistence Exception foreign key contraint fails in hibernate

2 Answers2