void callback(HttpServletRequest req,
HttpServletResponse resp,
Map authnIdentifiers,
AuthenticationSourceKey authenticationSourceKey,   
AuthenticationSelectorContext authnSelectorContext);
PingFederate calls the callback() method after a selected authentication source is authenticated against. The callback() method allows authentication selectors to update resulting attributes, set cookies, or perform other custom functions.
Note:

Writing content to the resp object in the callback() method is not supported, and doing so may result in unexpected behavior. Setting cookies is acceptable.