Change your namedquery like
Code:
<query name="PostingListByCategoryId"><![CDATA[
from CategorizedItem ci where ci.id.categoryId in (:cids)
]]></query>
and the calling code as
Code:
List l = new ArrayList();
//Populate the List
session.getNamedQuery("PostingListByCategoryId").setParameterList("list", l);
But thats purely using Hibernate.
As far as Spring is concerned, I can see an API like
getHibernateTemplate().findByNamedQuery(namedquery, Object value);
Maybe you can create your list and pass it as the value ?