How to load a set of objects when Hibernate Lazy Fetchtype is used?

Question

I have a Hibernate domain class (let's say PetOwner) with a one to many relationship with another class(Pets)

[PetOwner (1)---------(*) Pet]

Due to a drastic change required to improve the performance I had to change the fetchtype of the getPets() method in PetOwner class to be lazy.

So the current mapping looks as follows

@OneToMany(cascade = {CascadeType.ALL}, fetch = FetchType.LAZY, mappedBy = "petowner")
public Set<Pet> getPets() {
    if (pets == null) {
       pets = new HashSet<Pet>();
    }
    return pets;
}

For some test classes, the getPets() method is used after a PetOwner is found using the retrievePetOwnerById() method. After the changes to mapping this causes LazyInitializationException.(As the object-graph is not fully loaded due to the change of fetch type)

I used a not elegant workaround by adding a method like the one shown below to the DefaultPetOwnerService.

public PetOwner retrievePetOwnerByIdWithPets(Long petOwnerId) {
        PetOwner petOwner = retrievePetOwnerById(petOwnerId);
        int size = petOwner.getPets().size();
        return petOwner;
    }

petOwner.getPets().size() has to be used because the pets won't be loaded till some operation on the list is done. When I use the new method, the LazyInitializationException can be overcome. But it's a hack and I'm searching a way to do this more neatly. Are there any suggestions?

Answer 1

In http://stackoverflow.com/questions/780603/hibernate-lazy-loading-doesnt-work-on-one-to-many-mapping-on-set/968686#968686 I reference a possible solution to your problem.

Answer 2

Try using Hibernate#initialize(Object) to initialize your object. It should resolve the collection reference.

I'm curious why you want "eager" fetching without setting the fetch type to be eager though.