CAS Client Filter - how to handle ticket validation exception

[Matteo Matteo]

Cas client 2.1.0 from yale.
The problem is that if you session has timed out and you press F5 for page reloading, than if there's the ticket parameter in request - you'll get an InternalError Exception caused by ticket validation.
The question is - what is the best solution for exception handling in this case and further redirect to CAS Server for authorization?
Thanks


javax.servlet.ServletException: Unable to validate ProxyTicketValidator [[edu.yale.its.tp.cas.client.ProxyTicketValidator proxyList=[null] [edu.yale.its.tp.cas.client.ServiceTicketValidator casValidateUrl=[https://casintern.local.company.de:8443/cs/proxyValidate] ticket=[234sd82378] service=[http%3A%2F%2Fexport4.company.com%2Fwdata%2Findex.jsp%3Fm%3D0] errorCode=[INVALID_TICKET] errorMessage=[Ticket '234sd82378' wurde nicht anerkannt] renew=false entireResponse=[<cas:serviceResponse xmlns:cas='http://www.yale.edu/tp/cas'>
	<cas:authenticationFailure code='INVALID_TICKET'>
		Ticket '234sd82378' wurde nicht anerkannt
	</cas:authenticationFailure>
</cas:serviceResponse>
]]]]
	edu.yale.its.tp.cas.client.filter.CASFilter.doFilter(CASFilter.java:382)


root cause 

edu.yale.its.tp.cas.client.CASAuthenticationException: Unable to validate ProxyTicketValidator [[edu.yale.its.tp.cas.client.ProxyTicketValidator proxyList=[null] [edu.yale.its.tp.cas.client.ServiceTicketValidator casValidateUrl=[https://casintern.local.company.de:8443/cs/proxyValidate] ticket=[234sd82378] service=[http%3A%2F%2Fexport.company.com%2Fwdata%2Findex.jsp%3Fm%3D0] errorCode=[INVALID_TICKET] errorMessage=[Ticket '234sd82378' wurde nicht anerkannt] renew=false entireResponse=[<cas:serviceResponse xmlns:cas='http://www.yale.edu/tp/cas'>
	<cas:authenticationFailure code='INVALID_TICKET'>
		Ticket '234sd82378' wurde nicht anerkannt
	</cas:authenticationFailure>
</cas:serviceResponse>
]]]]
	edu.yale.its.tp.cas.client.CASReceipt.getReceipt(CASReceipt.java:62)
	edu.yale.its.tp.cas.client.filter.CASFilter.getAuthenticatedUser(CASFilter.java:458)
	edu.yale.its.tp.cas.client.filter.CASFilter.doFilter(CASFilter.java:379)