JPA CascadeType.ALL 不删除子记录

Question

Consider this use case.

class Category {
   @OneToMany(cascade=CascadeType.ALL)
   List<Application> applications = new ArrayList<Application>();
}

class Application {
   @ManyToOne
   Category category;       
}

I understand that, On this case, when category will be deleted, application will also be deleted. But who takes care of join table? The Category_Application table generated for the relation.

Answer 1

The join table rows should always be deleted, regardless of cascade .

For a bi-directional ManyToMany to owning (non- mappedBy ) side will delete the rows.

Since you have a ManyToOne back, it seems you should be using a mappedBy , not a join table.

Is the issue that they are not being deleted, or are you getting a constraint error before they are deleted? Also ensure you collection is not empty when you call remove() . Try also removing everything from the collection before calling remove .

Answer 2

It sounds like this is the same issue as:

JPA CascadeType.ALL does not delete orphans

Basically, when you have a @OneToMany , JPA assumes by default that the child object has an independent lifecycle and may be associated to multiple parents. Deleting the parent does not necessarily delete the child. Specifying orphanRemoval=true in JPA 2.0 (or Eclipselink @PrivateOwned or Hibernate CascadeType.DELETE_ORPHAN ) tells JPA to remove the child records when the parent is deleted.

If you always want to tie the child record lifecyle to its parent, you might also want to consider @ElementCollection instead of @OneToMany, which will give similar behavior but not let you persist child objects independently of the parent. (ie, the child objects of an @ElementCollection are not @Entities.)