Hi everyone,

i am trying to use filter collections in my code but there is a problem, i am not able to understand what is happening in the code below which is from Hibernate reference documentation. It is not expained anywhere how to use collection filters.

what is this pk.getKittens(), is it returning all the kittens and what is Color.BLACK and Hibernate.custom(ColorUserType.class)

there is a question mark (?) in the where clause, is a query specified somewhere?

Collection blackKittens = session.createFilter(
pk.getKittens(),
"where this.color = ?")
.setParameter( Color.BLACK, Hibernate.custom(ColorUserType.class) )
.list()
);

Please help.
thanks

Yes - createFilter actually creates a Query object. Maybe the code makes more sense like this:-



pk.getKittens() is the original mapped collection.
Color.BLACK is the value that we're setting for the parameter in the query and Hibernate.custom(ColorUserType.class) is its type.
"where this.color = ?" is the entire query supplied by the user - Hibernate introduces its own from clause to match to collection and aliases the elements to 'this'.

Hope that helps,
Cheers,
Rich.

Hi Rich,

I am trying to use collection filters but i am getting this error:
The collection was unreferenced

Here is what i am doing:

-- I have a xml mapping file which has a query defined:

<query name="tmp" cacheable="true">
<![CDATA[
SELECT M1 as Milestone
FROM Milestone M1
]]>
</query>

Next, i have a method which returns a list i.e.

public List tmp() {

Query query= getSession().getNamedQuery("tmp");

Query filterQuery = getSession().createFilter( getSession().getNamedQuery("tmp"), "");

return filterQuery.list();
}

now whenever i call this method, i get an error: The collection was unreferenced in line which says: return filterQuery.list();