Spring Data JPA - ManyToOne unable to delete child without modifying parent list - spring

Question

I struggle for a week with the following problem:
How is it possible to delete a child entity through a repository without modifying the List on the owning (parent) side of the relation?
Thanks in advance.
I am hoping for some answers!
The child class:
#Entity
#Table(name = "child")
#Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
public class Child implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
#SequenceGenerator(name = "sequenceGenerator")
private Long id;
#ManyToOne
private Parent parent;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public Long getParent() {
return parent;
}
public void setParent(Parent parent) {
this.parent = parent;
}
}
And the parent class:
#Entity
#Table(name = "parent")
#Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
public class Parent implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
#SequenceGenerator(name = "sequenceGenerator")
private Long id;
#OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval = true)
#JsonIgnore
#Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
private Set<Child> children = new HashSet<>();
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public Set<Child> getChildren() {
return children;
}
public void setChildren(Set<Child> children) {
this.children = children;
}
public Parent addChild(Child child) {
this.children.add(child);
child.setParent(this);
return this;
}
public Parent removeChild(Child child) {
this.children.remove(child);
child.setParent(null);
return this;
}
}
And here the test:
#Test
#Transactional
public void testParentToChildRelationShip() {
Parent parent = new Parent();
Child child = new Child();
parent.addChild(child);
parent.addChild(new Child());
parent.addChild(new Child());
parent.addChild(new Child());
parentRepository.save(parent);
Assertions.assertThat(parentRepository.count()).isEqualTo(1L);
Assertions.assertThat(childRepository.count()).isEqualTo(4L);
childRepository.delete(child);
Assertions.assertThat(parentRepository.count()).isEqualTo(1L);
// fails
Assertions.assertThat(childRepository.count()).isEqualTo(3L);
parentRepository.delete(parent.getId());
Assertions.assertThat(parentRepository.count()).isEqualTo(0L);
Assertions.assertThat(childRepository.count()).isEqualTo(0L);
}
The test would work if I insert before deleting the child,
child.getParent().removeChild(child);
but I want to avoid calling this.
Is there a way to make it work with just calling the Child-JPA-Repository.delete method? Or other annotations that I missed?

Answer 1

Since child has association with parent you are facing this issue, you need to remove the link between child and parent either using
parent.removeChild(child);
or
child.getParent().removeChild(child);

Answer 2

Remove these lines from your parent class and also setter and getter of children
#OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval = true)
#JsonIgnore
#Cache(usage = CacheConcurrencyStrategy.NONSTRICT_READ_WRITE)
private Set<Child> children = new HashSet<>();
I think you can remove child mapping from your parent class so you can easily delete the child row using ChildRepository delete() method but problem is that you have to save your child manually using ChildRepository save(). You can not save child object with parent object using ParentRepository. Change your Test code like below for saving child and parent
Parent parent = new Parent();
Parent parent = parentRepository.save(parent);
Child child = new Child();
child.setParent(parent);
childRepository.save(child);