How to wire tap a message channel in java dsl? - spring-integration

Question

I am trying Java dsl in spring integration. I am trying to wiretap a channel. But getting error,
#ContextConfiguration
#EnableIntegration
#IntegrationComponentScan
public class DemoApplication {
public static void main(String[] args) {
ApplicationContext ctx = new AnnotationConfigApplicationContext(DemoApplication.class);
CustomGtwy service = ctx.getBean(CustomGtwy.class);
service.pushMessage("Manoj");
}
#Bean
public MessageChannel loggerChannel(){
return MessageChannels.direct().get();
}
#Bean
public MessageChannel pushAssetIdChannel() {
return MessageChannels.direct()
.interceptor(new WireTap(loggerChannel()))
.get();
}
#Bean
public IntegrationFlow pushAssetIdFlow() {
return IntegrationFlows.from("pushAssetIdChannel")
.handle(new GenericHandler() {
#Override
public String handle(Object arg0, Map arg1) {
// TODO Auto-generated method stub
return "Success";
}})
.get();
}
#MessagingGateway
public interface CustomGtwy{
#Gateway(requestChannel="pushAssetIdChannel")
String pushMessage(String s);
}
#Bean
public IntegrationFlow logger(){
return IntegrationFlows.from("loggerChannel").handle(new GenericHandler() {
#Override
public String handle(Object arg0, Map arg1) {
// TODO Auto-generated method stub
return "Success";
}}).channel("nullChannel").get();
}
}
In the above code, if i try to put message in the pushAssetIdChannel, i am getting Dispatcher has no subscribers for channel 'unknown.channel.name'
If the interceptor is not there, it is working.

Answer 1

Not sure what's going on with your case, but that works for me with the latest 1.0.2 version:
#ContextConfiguration
#RunWith(SpringJUnit4ClassRunner.class)
#DirtiesContext
public class SO31348246Tests {
#Autowired
private MessageChannel pushAssetIdChannel;
#Test
public void testIt() {
this.pushAssetIdChannel.send(new GenericMessage<>("foo"));
}
#Configuration
#EnableIntegration
public static class ContextConfiguration {
#Bean
public MessageChannel loggerChannel() {
return MessageChannels.direct().get();
}
#Bean
public MessageChannel pushAssetIdChannel() {
return MessageChannels.direct()
.interceptor(new WireTap(loggerChannel()))
.get();
}
#Bean
public IntegrationFlow pushAssetIdFlow() {
return IntegrationFlows.from("pushAssetIdChannel")
.handle(System.out::println)
.get();
}
#Bean
public IntegrationFlow logger() {
return IntegrationFlows.from("loggerChannel")
.handle((p, h) -> {
System.out.println(p);
return p;
})
.channel("nullChannel")
.get();
}
}
}
I see both SOUTs in logs.
UPDATE
Your class works for me after fixing #ContextConfiguration to the normal #Configuration annotation :-).
Without the last one the framework considers your DemoApplication as lite configuration, just because you have there #Bean methods, but it does not do it like the full one and doesn't proxy it to allow to use bean method reference like you do with loggerChannel() in the WireTap constructor.
So, with lite we jsut invoke that method and get a fresh MessageChannel object, but it isn't a bean in the application context. That's why you end up with the Dispatcher has no subscribers.