Call Function in OAF

The segment below calls a custom function with 1 input parameter of type Varchar and returns a Varchar :

   OAApplicationModule oam = pageContext.getApplicationModule(webBean); 

   String sql =   "BEGIN :1 := xx_custom_pkg.call_custom_function (:2); END;";

  OracleCallableStatement cs =
                            (OracleCallableStatement)oam.getOADBTransaction().createCallableStatement(sql,2);

                        try {
                             //Register your function output...
                            cs.registerOutParameter(1, Types.VARCHAR, 0, 2000);
                            //Your input parameter below...
                            cs.setString(2, LinesRow.getAttribute("ReportLineId").toString());
                            cs.execute();
                            String p_res = cs.getString(1);
                            cs.close();       
                            }
                        catch (Exception ex) {
                                        pageContext.writeDiagnostics(this,
                                                                     "Error:" + ex.toString(),
                                                                     OAFwkConstants.PROCEDURE);
                           }