How to use temporary Channel in Spring Integration?

Question

I'm new in Spring Integration, I'm trying to get the message from temporary channel.

Reading the documentation there is a temporary channel use by spring. I guess it named NullChannel

I need my gateway returns the value from temporary channel.

http controller -> gateway -> direct channel -> activator 1 -> queue channel -> activator 2

So my activator 2 will put the new value into temporary channel, so the gateway will retrieve the value from temporary channel

@MessageEndpoint
public class Activator2 {
    
@Autowired
private NullChannel nullChannel;

@ServiceActivator(inputChannel = "asyncChannel")
public void plus(Integer message){
    try {
        message++;
        Thread.sleep(2000);
        nullChannel.send(MessageBuilder.withPayload(message).build());
        log.info("Activator 2: " +message );

    } catch (InterruptedException e) {
        log.error("I don't want to sleep");
    }
    
}
}

it not working. I'm not sure if everything is well connected

Answer 1

NullChannel is like /dev/null in Unix; it just discards the value.

@ServiceActivator(inputChannel = "asyncChannel")
public Integer plus(Integer message){
    return message;
}

will automatically do what you want.

If there is no outputChannel, the framework sends the result to the replyChannel header.