I have a named query that looks like this:

select new PiSimilarity(p.pi,n.similarity)
from Neighbours as n
join n.id.sequenceA as s
join s.proteins as p
where n.id.sequenceB=:sequence
and n.similarity>=:similarity

When running it i get:
net.sf.hibernate.QueryException: could not find constructor for: PiSimilarity: <init>

If i replace "new PiSimilarity(p.pi,n.similarity)" with "p.pi,n.similarity" it works ok...

the ctor for PiSimilarity is "public PiSimilarity(Integer pi, Float similarity)"
and the protein.pi and neighbours.similarity columns are defined as Integer and Float, respectively..

any idea why it doesnt work?

I would guess that the types don't match from the resultset and the types on the class. I can see you claim that they match but not matching is the only explanation the I can think off.

Ah, it expects primitive types, ie. int, float.

This kinda sucks and should be changed....

when using the "select p.pi, n.similarity..." variant, i get an Object array back with 2 objects in it, at index 0 a java.lang.Integer and at index 1 a java.lang.Float.. So my types do match....

i got inspired from the hibernate reference doc, which has the following example:

select new Family(mother, mate, offspr)
from eg.DomesticCat as mother
join mother.mate as mate
left join mother.kittens as offspr

but mother, mate and offspr are not primitive types.. theyre real classes (and even persistent ones too :o).. or is this example just wrong???

I just changed the ctor to "PiSimilarity(int pi, float similarity) and it seems to be working.. but i think you're right, the ctor arguments should match the types of the attributes used when calling the ctor...