@Override
public void start() {
Map<String, Appender> map = config.getAppenders();
for (Route route : routes.getRoutes()) {
if (route.getAppenderRef() != null) {
Appender appender = map.get(route.getAppenderRef());
if (appender != null) {
String key = route.getKey() == null ? DEFAULT_KEY : route.getKey();
if (appenders.containsKey(key)) {
if (DEFAULT_KEY.equals(key)) {
LOGGER.error("Multiple default routes. Only the first will be used");