EJB-QL Aggregate functions 3.2.4

[mozheyko_d]

Yes !!!
They have made it.

LocalHome interface:

 ...
 public Collection findPaysSum( Timestamp time1, Timestamp time2) throws FinderException;
 ...

ejb-jar.xml:

 ...
 <ejb-ql>
 [CDATA[
 SELECT SUM(p.summa) FROM pay p WHERE p.moment > ?1 and p.moment < ?2
 ]]
 </ejb-ql>
 ...

Use this method:

 ...
 Iterator it = payHome.findPaysSum( Timestamp.valueOf( time1), Timestamp.valueOf( time2)).iterator();
 if( it.hasNext()){
 Object pk = ( ( EJBLocalObject)it.next()).getPrimaryKey();
 return ( Double)pk;
 }
 ...

But if the result of SUM function is null, this method throws the Exception:
javax.ejb.TransactionRolledbackLocalException: Attempt to get lock ref with a null object; CausedByException is: Attempt to get lock ref with a null object

How it is possible to bypass it?

Thanks

[aloubyansky]

How would you describe what you are doing?
It's obviously a misuse. Aggregate functions are allowed only in ejbSelect's and they never return EJB[Local]Object's.

[mozheyko_d]

Yes, i know it.
But this code works !
Maybe you explain me how2 use SUM or another aggregate functions ?
Please, show me the little properly sample.

[aloubyansky]

There is some info in the EJB2.1 spec.
11.2.7.2 Aggregate Functions in the SELECT Clause

[mozheyko_d]

Thank you, Alex.
But i dont understand: 3.2.4 support EJB2.1 ? or 2.0 ?

[aloubyansky]

No, 2.0. Just the QL syntax was extended to support 2.1.