Why we use Set

Question

I've always seen people using interfaces of collection framework when there is a One-to-many relationship in Entity classes. For Example if Author has written many books then it Looks like this:

@OneToMany(mappedBy = "author")
private List<Book> books;

and why not

@OneToMany(mappedBy = "author")
private ArrayList<Book> books;

Or

@OneToMany(mappedBy = "author")
private Set<Book> books;

and not

@OneToMany(mappedBy = "author")
private HashSet<Book> books;

So why to use interfaces and not implementations of collection framework?

For the same reasons you have interfaces in the first place. Doesn't matter if hibernate is used or not — XtremeBaumer, Aug 12 '19 at 07:41

score 2 · Accepted Answer · answered Aug 12 '19 at 07:44

The recommended way is to use Interfaces rather than concrete types as Hibernate behind the scene injects it's own implementations ( like PersistenBag, PersistentSet etc.) to provide it's lazy loading / dirty check and other magic. Checkout this answer too.

1 Answers1