protected void onExpiration(Session s, ExpiredSessionException ese, SessionKey key) {
        LOGGER.trace("Session with id [{}] has expired.", s.getId());
        try {
            onExpiration(s);
            notifyExpiration(s);
        } finally {
            afterExpired(s);
        }
    }
Looks up a session from the underlying data store based on the specified session key.

@param key the session key to use to look up the target session.
@return the session identified by {@code sessionId}.
@throws UnknownSessionException if there is no session identified by {@code sessionId}.
core/src/main/java/org/apache/shiro/session/mgt/AbstractValidatingSessionManager.java