http://steven-wiki.readthedocs.org/en/latest/security/cas-tomcat/
http://wenku.baidu.com/view/13a57761783e0912a2162a94.html
restful:
http://jasig.github.io/cas/4.0.0/protocol/REST-Protocol.html
http://jasig.275507.n4.nabble.com/Setting-up-the-RESTlet-servlet-on-CAS-3-3-5-td2068602.html