In the apache site it says: Cancel handlers - DispatchAction, LookupDispatchAction, and MappingDispatchAction - Now provide default cancel handler that can be overridden. It also also possible to specify the default handler name.
I'm trying to have a cancel button on a form that works with dispatchAction.
The method to handle a cancel button is "cancelled". (see the javadoc). You need to overrride that method and include whatever logic you want executed when the cancel button is pressed.
It also appears that you may have to send some value in the "operation" parameter since that is the declared handler parameter. Adding an onclick event to the button might do the trick. Something like this: