When

EAGER. In this case data will be delivered immediately. So we no need extra fetch for get this data but payload can be significantly large.

@OneToOne(fetch = FetchType.EAGER)
private MyEntity entity;

LAZY. In this case data will be delivered when it is necessary. So we need extra fetch for get this data. Collection is lazy by default because list can we large.

@OneToMany(fetch = FetchType.LAZY)
private List<MyEntity> entities;

How

JOIN. Join fetch (left/outer join). This is great for to one associations.

select e from MyEntity e
join fetch e.subEntities p
where p.id = 42

SELECT. Follow-up selects. This is default style for collections.

select e from MyEntity e where e.id = 42

BATCH. Fetches multiples entries when one is accessed.

@OneToMany
@BatchSize(size = 5)
List<MyEntity> entities;