html:cancel button throwing exception

[faraz irfan]

hi friends
I am using <html:cancel> button in my application as follows
<html:cancel>
<bean:message key="button.cancel"/>
</html:cancel>

but when i press Cancel button on my jsp it gives me an error like:
The server encountered an internal error () that prevented it from fulfilling this request.

i have also used
if(isCancelled(request)){
System.out.println("Cancelled Operation performed");
return mapping.findForward("mainpage");
}
in my execute meathod in the action class.

kindly help me out..
thanks in advance.. :-)