code>UIViewRoot</code> being different than
 the current one.
 </p>
 </li>

 <li>
 <p>
 The session, that happened to be active when the bean was created, expires. If no session existed when the bean was
 created, then this circumstance does not apply.
 </p>
 </li>

 </ul>

 <p>
 In the session expiration case, the runtime must ensure that
 <a href="../context/FacesContext.html#getCurrentInstance()"><code>FacesContext.getCurrentInstance()</code></a> returns a valid instance if it is called during the
 proce