Eager Load a ManyToOne Lazy Collection in Spring JPA Transaction

Asked Jul 05 '17 at 14:41

Active Jul 05 '17 at 14:41

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I have Lazy Loaded OneToMany, ManyToMany and ManyToOne collections in my Spring JPA entities. Whenever I want to load my OneToMany and MantToMany collections into my transaction, I use this trick

school.getStudents().size()

In a similiar fashion, I would like to load my ManyToOne collection (say School->City). How would I eagerly load my City data into my transaction in some 'simple way' similiar to the OneToMany collection show above.

My alternatives right now are

Change the ManyToOne to Eager loading
Write a JPQL query fetching the city while fetching the school data. But this is not very flexible if I have multiple ManyToOne entities and any additional fields involves changing the JPQL query.

Would appreciate any suggestions.

asked Jul 05 '17 at 14:41

HopeKing

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Call a getter? I.e getToOne().getId() – Martin Frey Jul 05 '17 at 15:03
yes, why not `school.getCity()` (in transaction scope) ? – xerx593 Jul 05 '17 at 15:20
@Frey school.getCity() throws an exception ! I think that is the normal behaviour since it is proxied because of Lazy Loading. – HopeKing Jul 05 '17 at 15:23
Option 2 is what I usually do ... or you can use `CriteriaBuilder` ... – K.Nicholas Jul 05 '17 at 15:49
Possible duplicate of [How to load lazy fetched items from Hibernate/JPA in my controller](https://stackoverflow.com/questions/15359306/how-to-load-lazy-fetched-items-from-hibernate-jpa-in-my-controller) – K.Nicholas Jul 05 '17 at 15:51
You will have to load the relation in the same transaction. Exactly the same way as for collection size(). – Martin Frey Jul 05 '17 at 18:59
Yes, I get that as mentioned in my post. wondering if there is a method similiar to .size() *ToMany – HopeKing Jul 06 '17 at 02:42

Eager Load a ManyToOne Lazy Collection in Spring JPA Transaction

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