How-to get the JSF application context path?

Question

I want to do a redirect from within a JSF backing bean. How do I get the application context path?
I plan to do this in the constructor of the backing beans in order to validate the user has previously logged in.
public BackingBeanName()
FacesContext facesContext = FacesContext.getCurrentInstance();
HttpSession session = HttpSession)facesContext.getExternalContext().getSession(false);
HttpServletRequest request = (HttpServletRequest)facesContext.getExternalContext().getRequest();
userid = (String)session.getAttribute("userid");
if (userid == null) {
logger.info("userid attribute is not in session");
ExternalContext ec = facesContext.getExternalContext();
appContextPath = ???????????????????????;
String redirectTo = appContextPath + "/logon.jsp";
try {
ec.redirect(redirectTo);
catch (IOException e) {
String msg = "redirect to " + redirectTo + " failed";
logger.severe(msg);
return; // throw an exception instead of return;
Regards,
Al Malin

Answer 1

Frank, your suggestion of using JSF global navigation to the logon page looks like what I need but I need some advice implementing it.
My backing bean constructor looks like this:
public Search()
FacesContext facesContext = FacesContext.getCurrentInstance();
String userid = GpaUtil.getSessionUserid(facesContext);
if (userid == null)
logger.info("session userid not found, going to logon page");
??????? What goes here ????????
??????? I think I need to fire an event but I'm not sure how to do it, ????????
??????? let alone if this is what needs to be done ????????
??????? or even if this is the right spot in the code ????????
gpas = ProductApproval.retrieveList("1=1","1");
FWIW, the navigation rule looks like this:
<navigation-rule>
<navigation-case>
<from-outcome>goLogon</from-outcome>
<to-view-id>/logon.jsp</to-view-id>
</navigation-case>
</navigation-rule>
Your help is greatly appreciated.
Regards,
Al Malin