The problem is the following: I need to serialize the user session, so, it will still be present after a server restarts.
Using JavaEE and Tomcat 7 works fine with implements Serializable, but the problem is the FacesContext. Indeed, after restarting the server, FacesContext.getCurrentInstance() returns null, and therefore I cannot access the message bundle (and therefore my message.properties cannot be found anymore).
So, how do I keep the FacesContext when restarting Tomcat?