In the case of a listener (Action- or ValueChange), the answer is yes...FacesContext can be accessed by calling the static getCurrentInstance method: FacesContext.getCurrentInstance(). FacesContext essentially represents the request as it travels through the JSF lifecycle.
I am guessing (but I'm not sure) that the same does not apply to filters. Although the request itself is available, FacesServlet may not have instantiated FaceContext yet. But you can get at the HttpRequest object in the filter, because it is a parameter passed into the doFilter method (OK, it's passed as a ServletRequest, but can be cast, if I'm not mistaken).
Joined: Jan 17, 2002
I know it can be accessed but the question is is it appropriate to obtain the request object in a (Listener/Filter) using a FacesContext