In a JPA 2.0 application, a dual JOIN FETCH statement returns incorrect results when one of the properties is a list with FetchType.LAZY; the list property has all records duplicated after execution of the query:
SELECT p FROM test_parent p JOIN FETCH p.children1 JOIN FETCH p.children2

Here we have one parent entity class and two child entity classes, associated via @OneToMany relationships from the parent class. The parent is tied to one child class via a Map, and to the other via a List. Both collection properties are FetchType.LAZY:

public class Parent {
@Id
@Column(name = "parentId", unique = true, nullable = false)
public int id;

@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "parent")
@MapKey(name = "myval")
public Map<Integer, Child1> children1 = new HashMap<>();

@OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL, mappedBy = "parent")
public List<Child2> children2 = new ArrayList<>();
}

I created a JIRA defect for this defect (HHH-7895), but was asked to post to the forum first. A full test case that includes the child classes is attached to the defect.

Comments appreciated.

Thanks,

Uli

Anyone?