code: public void add(final EventListener<T> eventListener) {
          if (eventListener.subscriber()) {
              if (debug) logger.debug("subscription to channel <> from <> ", name, eventListener);
              listeners.add(eventListener);
              stats.recordLevel(eventBusName + "::" + name, listeners.size());
          } else {
              if (debug) logger.debug("consumer to channel <> from <> ", name, eventListener);
              consumer = eventListener;
          }
      }
docs: Add an event listener to the channel
  There can only be one consumer and many listeners.
  
  @param eventListener eventListener