session.createQuery(
	"select a from Product a " +
	"where " +
	"coalesce(a.description, :description) = :description)", Product.class)
.setParameter( "description", "desc" )
.getResultList();

select
	product0_.productId as productI1_35_,
	product0_.description as descript2_35_,
	product0_.cost as cost3_35_,
	product0_.numberAvailable as numberAv4_35_
from
	Product product0_ 
where
	coalesce(product0_.description, ?)=?