Reply Channel for Messaging Gateway using Java DSL - spring-integration

Question

I have a REST API which receives a POST request from a client application.
#Autowired
private EdiTranslationEvents.TransformToString transformToString;
#PostMapping("/testPost")
#ResponseStatus(HttpStatus.OK)
public String testPostLogging(#RequestBody Student student) {
log.info("In controller....");
System.out.println(this.transformToString.objectToInputGateway(student));
return "testPost logging";
}
As you can see, in the controller, I have an autowired messaging gateway and I am using it to send data to a channel.
#Configuration
#EnableIntegration
public class EdiTranslationEvents {
#Component
#MessagingGateway
public interface TransformToString {
#Gateway(requestChannel = "inputObjectChannel")
String objectToInputGateway(Student student);
}
#Bean
public IntegrationFlow inputObjectString() {
return IntegrationFlows.from(inputObjectChannel())
.transform(Transformers.objectToString())
.log(LoggingHandler.Level.DEBUG, "com.dash.Logger")
.get();
}
}
When I send data to the REST API, the API just hangs. The gateway does not return anything. I have the return type specified, and I was assuming that the gateway creates a temporary reply channel and sends the response to that channel.
However, I am not doing anything in the DSL configuration for creating or managing a reply. So, how do I send a reply back to the reply channel from the DSL flow?

Answer 1

Your current flow does not return a value, you are simply logging the message.
A terminating .log() ends the flow.
Delete the .log() element so the result of the transform will automatically be routed back to the gateway.
Or add a .bridge() (a bridge to nowhere) after the log and it will bridge the output to the reply channel.