After doing a lot of search, without finding a solution I hope to find one here

having a Map with a Entity as key and a Long a value I try to find a hql query to join to the key of the Map:


class Owner {
@CollectionOfElements()
@JoinTable(name = "Amounts", joinColumns = {@JoinColumn(name = "ownerId")})
@Column(name = "amount")
@MapKeyManyToMany(joinColumns = {@JoinColumn(name = "entityId")})
Map<Entity, Long> amounts;
}

so the question is, how to join from owner to entity

select entity from Owner owner join key(owner.amounts) as entity
select entity from Owner owner join owner.amounts.key as entity
select entity from Owner owner join index(owner.amounts) as entity
select entity from Owner owner join owner.amounts.index as entity
select entity from Owner owner, Entity entity where index(owner.amounts)=entity

all fails.

Is there a way to do it? I'm using hibernate 3.3.2

The general advice for dealing with Map collections is to stay away. Stay very away. The spec is fine but I don't think any implementors get it right.

That said, given the following "rows" in your database:

• Entity#1
• Entity#2
• Owner.amounts[Entity#1] = 800
• Owner.amounts[Entity#2] = 400

will give you:

• Entity#2 | 400
• Entity#1 | 800

So use the hibernate-specific built-in index(). For reference, here's what the JPA2 specification actually calls for:

But Hibernate doesn't support this: http://opensource.atlassian.com/project ... e/HHH-5396

You could also try mapping with JPA2 annotations just for the heck of it:

and then let me know if you find it as broken as I do :). Yes, I'm bitter. I've had a heck of a lot of pain dealing with maps. I suspect a lot of it stems with the JPA2 compatibility toolkit, but thanks for letting me rant.

i found a query which seems to work:

select entity from Owner owner join owner.amounts as amount join amount.index as entity

Wow... I've never seen that.