JPA dynamic order by clause

Question

I need to dynamically build the order by clause of my query.
I tried this:
<named-query name="list">
  <query>
    <![CDATA[
      SELECT p FROM Person p
      ORDER BY :orderby
    ]]>
  </query>
</named-query>
@SuppressWarnings("unchecked")
public List<Person> list(String sort) {
  Query query = getEntityManager().createNamedQuery("list");
  query.setParameter("orderby", sort);
  return query.getResultList();
}But at runtime it throws an exception:
com.microsoft.sqlserver.jdbc.SQLServerException:
L'elemento SELECT identificato da ORDER BY 1 include una variabile nell'espressione che identifica la posizione di una colonna.
Le variabili sono consentite solo nell'ordinamento in base a un'espressione che fa riferimento a un nome di colonna.The translation of the italian message is something like:
The SELECT element identified by ORDER BY 1 includes a variable that identifies the position of a column.
The valid variables in the order by clause must refer to the name of a columnThe value of the parameter sort is_ the name of a column!
Any hint?

Answer 1

My solution was to append the order clause to an "namedQuery" like this:
- declare the named query as usual, with annotation
- create a simple helper function like findNamedQuery to find the query string for a given class and queryName (using reflection)
- if you need to execute the query without sort order - use EntityManager.createNamedQuery (as usual)
- BUT: if you want to sort data: use EntityManager.createQuery with the string obtained from findNamedQuery and the sort clause
I guess the is a performance penalty, but.. .it works.