Hibernate Lazy Loading Issue

Question

I mapped this entity in Hibernate 5

class A {
    private String code;
    private B child;

    @LazyToOne(LazyToOneOption.PROXY)
    @ManyToOne(fetch=FetchType.LAZY)
    @NotFound(action=NotFoundAction.IGNORE)
    @JoinColumns({...})
    public B getChild() { ... }
}

And my query to load only A is:

from A where a.code like :q

With this configuration Hibernate makes a select on A and on B entities. I don't want it to load B but only A

What am I missing?

Is that really the entire class? This technique only works if hibernate can generate a proxy for the class, but other contents of your class (like a nondefault constructor, or it being final) could prevent hibernate from generating a proxy. — Joeri Hendrickx
– Joeri Hendrickx, Commented Jun 29, 2016 at 10:59
This is all class. gist.github.com/stefanopulze/c921cf477c6713feee3f79e42a51fef6 — stefanopulze
– stefanopulze, Commented Jun 29, 2016 at 13:16
Consider using entity JPA 2.1 entity graphs: thoughts-on-java.org/jpa-21-entity-graph-part-1-named-entity — Gimby
– Gimby, Commented Jul 1, 2016 at 8:14
Do you really need the NotFound? My guess is that this is the cause of your problem: you're basically saying Hibernate: my schema is a mess, and although table A has a column containing the ID of a B, that B might not exist. So Hibernate needs to select from B to know if that B exists or not. Fix your data, add a foreign key constraint, remove the NotFound, and it shouldn't load from B anymore. — JB Nizet
– JB Nizet, Commented Jul 1, 2016 at 9:18

Spille · Accepted Answer · 2019-09-05 12:18:38Z

5

I had the same problem, which is caused by Hibernate ignoring the FetchType.LAZY, if NotFoundAction.IGNORE is defined.

After some googling I found a workaround: http://chekkal.blogspot.com/2012/09/hibernate-lazy-loading-and-notfound.html

public FieldType getField() {
    if(!Hibernate.isInitialized(field)) {
        try {
            Hibernate.initialize(field);
        }catch(EntityNotFoundException one) {
            field=null;
        }
    }
    return field;
}

In Hibernate 5.4.2 the exception has changed to EntityNotFoundException, but this workaround seems to work for me.

answered Sep 5, 2019 at 12:18

Spille

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2 Comments

Michael Forstner Over a year ago

Is this approach really faster than FetchType.EAGER and NotFoundAction.IGNORE?

Spille Over a year ago

Well, I don't think it's faster than FetchType.EAGER, when you access the field. But with the concept of lazy loading you can load data only when/if it is needed. Especially in big entity classes with several relationships, you might not want to load all relating objects by default, but only when required.

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