/** Cancel a SecurityContextToken */
public BaseSTSResponse cancel(
final BaseSTSRequest request, final IssuedTokenContext context)
throws WSSecureConversationException{
final CancelTarget cancelTgt = ((RequestSecurityToken)request).getCancelTarget();
final SecurityTokenReference str = cancelTgt.getSecurityTokenReference();
String id = null;
final Reference ref = str.getReference();
if (ref.getType().equals("Reference")){
id = ((DirectReference)ref).getURIAttr().toString();
}