code: protected MessageChannel resolveChannelName(String channelName) {
          if (channelResolver == null) {
              channelResolver = new BeanFactoryChannelResolver(beanFactory);
          }
          
          return channelResolver.resolveDestination(channelName);
      }
docs: Resolve the channel by name.
  @param channelName the name to resolve
  @return the MessageChannel object