How to get BOOLEAN from STORED FUNCTION

Question

We are calling legacy PLSQL stored procedures and functions via named queries. This has worked fine so far, but there are some functions which return the type 'BOOLEAN'. e.g.
FUNCTION some_function( some_argument IN NUMBER) RETURN BOOLEAN;
Where the return type is BOOLEAN calling the named query fails with
Local Exception Stack:
Exception [TOPLINK-4002] (Oracle TopLink - 10g Release 3 (10.1.3.0.0) (Build 060118)): oracle.toplink.exceptions.DatabaseException
Internal Exception: java.sql.SQLException: ORA-06550: line 1, column 13:
PLS-00382: expression is of wrong type
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored
Error Code: 6550
A couple of threads have hinted that what we are trying to do is not possible:
How to get BOOLEAN from STORED PROCEDURES
Re: Creating Named Query: from OracleCallableStatement
This would possibly be due to 'restriction in the OCI layer'. Can anyone help? Is there really now way to call a valid PLSQL stored function via a named query when the return type is BOOLEAN?
thanks

Answer 1

I can't comment on possible issues you might have with the driver, but if it can be done in JDBC, it should be possible in TopLink.
TopLink has the StoredFunctionCall which extends the StoredProcedureCall but adds an unnamed ouput parameter in the first spot of its parameter list. You will need to get the databasefield and set its type to BOOLEAN ie:
  DatabaseField returnField = (DatabaseField)yourStoredFunctionCall.getParameters().firstElement();
        returnField.setName(name);
        returnField.setSqlType(Type.BOOLEAN);Be sure not to use the setType() method, as I believe TopLink will try to use the Type.BIT when a boolean class is used as the classtype.
Best Regards,
Chris