Retrieving a child object after a commit on an entity object

Question

Lets say I retrieve an entity object that looks like this:

@Entity
public class Mother {
    ...

    @OneToMany(mappedBy = "mother",
               targetEntity = Child.class,
               fetch = FetchType.LAZY)
    public List<Child> getChildren() {
        return children;
    }
}

When retrieving the above object, I commit the transaction (and close the session associated with the object). Later on in the code, there is a need to retrieve the children. If I wanted to keep the fetch type as LAZY, is there a way to use the Mother object and still be able to call getChildren() to retrieve the children? Or would I have to just bite the bullet and query the children via the key of the Mother?

Answer 1

If I wanted to keep the fetch type as LAZY, is there a way to use the Mother object and still be able to call getChildren() to retrieve the children?

Not if the EntityManager has been closed.

Or would I have to just bite the bullet and query the children via the key of the Mother?

You could retrieve the children when getting the mother using a FETCH JOIN:

SELECT m
FROM Mother m LEFT JOIN FETCH m.children
WHERE m.id = :id

Other options include:

• using the Open Entity Manager in View pattern (if you are using a webapp)
• using an extended persistence context.