...
Receiving proxy tickets
You'll need to map the ProxyTicketReceptor servlet in your web.xml. This servlet must be available via https:
...
Asking for proxy tickets
Having mapped ProxyTicketReceptor, you're prepared to receive proxy tickets if the CAS server would send them to you. But you also need to configure the YaleCasContext to ask for them.
Configure the YaleCasContext with a CAS proxy callback URL whereat you have mapped the CASClient ProxyTicketReceptor servlet. The proxy callback URL must be https:.
...