private boolean isSessionValid(final HttpSession session) {
        try {
            session.getCreationTime();
            return true;
        } catch (IllegalStateException e) {
            // session has been invalidated
            LOGGER.warn("Invalid session - {}", e.getMessage());
            return false;
        }

    }
@return The time the token will expire (with a small buffer before the actual expiry included)
stroom-security/stroom-security-common-impl/src/main/java/stroom/security/common/impl/UpdatableToken.java