CODEWITHSUNDEEP
javahibernate
João Menighin
João Menighin

Reputation: 3225

Eager fetch an specific lazy property for a particular object

I have the following model:

@Table(name = "foo")
public class Foo {

    @ManyToOne(fetch = FetchType.LAZY)
    private Bar bar;

}

Using Entity Framework in .NET in a similar situation, I could eagerly bring the Bar property with something like:

context.Foo.Include(f => f.bar).First()

Is there anything equivalent with Hibernate?

My situation is that I'm saving an object with a lazy property into a session in my server. Then when I retrieve the session properties, I cannot access the lazy property for the Hibernate Session is already gone. I cannot put this property as EAGER because it is inherited from a @MappedSuperclass used by a lot of other classes.

Thanks for any help.

Upvotes: 0

Views: 1206

Answers (2)

Aleksandr Semyannikov
Aleksandr Semyannikov

Reputation: 1442

  1. JPA EntityGraph:

    @Entity
@Table(name = "foo")
@NamedEntityGraph(name = "foo.bar",
        attributeNodes = @NamedAttributeNode("bar")
)
public class Foo {

    @ManyToOne(fetch = FetchType.LAZY)
    private Bar bar;

}

Foo foo = entityManager.find(
    Foo.class,
    id,
    Collections.singletonMap(
        "javax.persistence.fetchgraph",
        entityManager.getEntityGraph("foo.bar")
    )
);

    You can see another example and more detail explanation there.

  2. Hibernate profiles:

    @Entity
@Table(name = "foo")
@FetchProfile(
    name = "foo.bar",
    fetchOverrides = {
        @FetchProfile.FetchOverride(
            entity = Foo.class,
            association = "bar",
            mode = FetchMode.JOIN
        )
    }
)
public class Foo {
    @ManyToOne(fetch = FetchType.LAZY)
    private Bar bar;
}


session.enableFetchProfile("foo.bar");
Foo foo = session.byId(Foo.class).load(id);

Upvotes: 3

Lorelorelore
Lorelorelore

Reputation: 3393

You can use a JPQL query with FETCH JOIN:

List<Foo> l = em.createQuery(
    "SELECT f FROM Foo f JOIN FETCH f.bar", Foo.class)
    .getResultList();

In this way all Foo class instances will be loaded with all Bar instances already fetched. You can tailor the query to fit your needs.

Upvotes: 1

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