JPA/hibernate sorted collection @OrderBy vs @Sort

Question

I would like to have a collection of child objects (here cat-kitten example) that are ordered. And keep their order on adding of new elements.

@Entity 
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Answer 1

If you want to avoid non-standard annotations, you could make kittens use some sorted Collection implementation. This would ensure that kittens is always in sorted order. Something like this:

@Entity 
public class Cat {
  @OneToMany(mappedBy = "cat", cascade = CascadeType.ALL)
  @OrderBy("name ASC")
  private SortedSet kittens = new TreeSet<>();
}

Note that this approach also requires Kitten to implement Comparable (alternatively, you could pass a Comparator to your TreeSet constructor). Also, I'm using a Set because I'm not aware of any standard sorted List implementation and I'm assuming the Cat does not have any clones in its litter =p.

Update: I'm not sure how picky Hibernate is with its getter/setter definitions, but with EclipseLink I've been able to remove a setter entirely and wrap the List returned by my getter in a Collections.unmodifiableList(...) call. I then defined special methods for modifying the collection. You could do the same thing and force callers to use an add method that inserts elements in sorted order. If Hibernate complains about not having the getter/setter, maybe you could change the access modifier? I guess it comes down to how far you're willing to go to avoid non standard dependencies.