doFilter(ServletRequest request, ServletResponse response, FilterChain chain) In this method, we check if the user has been authenticated already and if they have then we let the request through,
otherwise we check for a cas ticket as a request parameter, if it is not there then we redirect to cas for login.
In this method, we check if the user has been authenticated already and if they have then we let the request through,
otherwise we check for a cas ticket as a request parameter, if it is not there then we redirect to cas for login. If it is
there then we attempt to validate the ticket. If the ticket is valid then we redirect them back to thier originating request,
otherwise we redirect them back to CAS again.
See Also:javax.servlet.Filter.doFilter(javax.servlet.ServletRequestjavax.servlet.ServletResponsejavax.servlet.FilterChain)