On Thu, Apr 4, 2013 at 3:23 PM, BingXin Lu <soulsophia@gmail.com> wrote:

Thanks a lot, it is a solution. However, I think it is more user-friendly to give user instant prompt when detecting conflict in the database, so that user can decide to override current record in the database or keep current record and stop running the tool again.

I'm not aware of anything like that being done via the <param>'s <validator> tag... but that is the appropriate place for any checks on a parameter before the execute button is pressed. Peter P.S. Don't forget to include the mailing list in replies.