Java – JPA – delete children from the onetomany relationship

In the @ onetomany relationship, if I want to delete a child, do I need to explicitly delete the child from the parents' collection, or is it sufficient to delete the child only?

For example, people and telephones Everyone has a lot of phone numbers If I want to delete a phone number from a person, it's enough:

EntityManager.remove(phone);

Or I need to do this in advance:

Person.getPhone().remove(phone);

Not to mention, the cascadetype is set to merge

Solution

You need to explicitly delete a phone from the phone collection. Using entitymanager to delete a phone is not enough

On the other hand, using orphan removal may be sufficient, so if you delete an entity from the collection, it will be deleted automatically It's like:

@OneToMany(mappedBy="person",orphanRemoval="true")
private List<Phone> phones;

See also: http://docs.oracle.com/cd/E19798-01/821-1841/giqxy/index.html

If the parent entity is also deleted, cascade Remove deletes only child entities Cascase. Merge has nothing to do with this problem