How to force eager loading with CrudRepository in spring-data?

Question

I have an entity containing a List that is thus lazy loaded by default:

interface MyEntityRepository extends CrudRepository<MyEntity, Long> {

}

@Entity
public class MyEntity {
    @Id
    private Long id;

    @OneToMany(mappedBy = "bar") //lazy by default
    private List<Bar> bars;
}

@Entity
public class Bar {
    //some more
}

Question: How can I force eager loading when executing repository.findOne(id)?

Solution 1

I needed this too and as I'm calling the dao inside a service object that is insise a transaction I call call the get method so no exception and I was able to fetch the records. Something like in java 8:

public ProductEntity findProduct(int id) {
    ProductEntity p = productRepository.findOne(id);
    p.getPresentations().stream().count();
    return p;
}

p.getPresentations().stream().count(); will force the fetch, I know is not a clean way to do it but it gets the job done in the mean time

Solution 2

You can force eager fetch writing custom HQL query with left join fetch, eg:

interface MyEntityRepository extends CrudRepository<MyEntity, Long> {
    @Query("select e from MyEntity e left join fetch e.bar b where e.id = ?1")
    MyEntity findOne(long id)
}

Comments

[Jebil]

@OneToMany(fetch=FetchType.EAGER) will this help ?

[membersound]

I know I can force the eager mode like this. But I want to stick to the lazy default and just force eager on all lists on one specific select.

[Jebil]

or you can use MyEntity p = (MyEntity) sess.get(MyEntity.class, id); Hibernate.initialize(p.getBars());

[membersound]

So that would imply writing my own criterea. Which is fine in general, but I hope spring-data would bring something for this.

[membersound]

To quote myself: "I know I can force the eager mode like this. But I want to stick to the lazy default and just force eager on [...] one specific select"

[Tomasz Fijałkowski]

This solution generate more then one query.

[Tien Do Nam]

Can you show the source? I think that findBy and findAllBy does not make any difference.