Custom Inbound channel adapter to invoke a Pojo service

Question

I need to start/stop an Ftp flow depending on the size of the incoming folder. I have a service that verifies the folder size:

@Service
public class IncomingFolderChecker  {

  private static final int MAX_ALLOWED_SIZE = 2000000;

  @Value("${sftp.incoming}")
  private String incomingDir;

  @Autowired
  private MessageChannel controlChannel;

  public void checkFolderSize() {
    if (FileUtils.sizeOfDirectory(new File(this.incomingDir)) > MAX_ALLOWED_SIZE) {
      controlChannel.send(new GenericMessage<>("@sftpInboundAdapter.stop()")); // typo: was 'start()'
    } else {
      controlChannel.send(new GenericMessage<>("@sftpInboundAdapter.start()"));
    }
  }
}

I know that the control bus allows to do this. But that's all I know about Spring Integration. How can I hook this up using Java-DSL ?

Answer 1

First of all both your branches of the condition uses the same start() command. I guess one of them should be stop(). You code is correct as far as a controlChannel is an input channel for the Control Bus component. To do that with Java DSL you only need such a simple bean:

    @Bean
    public IntegrationFlow controlBusFlow() {
        return IntegrationFlows.from("controlChannel")
                .controlBus()
                .get();
    }

If that's not a question, please clarify.

UPDATE

Everything together with the Spring Integration style and its Java DSL:

    @Bean
    public IntegrationFlow controlSftpInboundAdapter(@Value("${sftp.incoming}") String incomingDir) {
        return IntegrationFlows
                .from(() -> FileUtils.sizeOfDirectory(new File(incomingDir)) > MAX_ALLOWED_SIZE,
                        e -> e.poller(pollerFactory -> pollerFactory.fixedDelay(1000)))
                .<Boolean, String>transform(p -> "@sftpInboundAdapter." + (p ? "start()" : "stop()"))
                .controlBus()
                .get();
    }