Spring integration: discardChannel doesn't work for filter of integration flow - spring

Question

I faced with a problem when I create IntegrationFlow dynamically using DSL.
If discardChannel is defined as message channel object and if the filter returns false - nothing happens (the message is not sent to specified discard channel)
The source is:
#Autowired
#Qualifier("SIMPLE_CHANNEL")
private MessageChannel simpleChannel;
IntegrationFlow integrationFlow = IntegrationFlows.from("channelName")
.filter(simpleMessageSelectorImpl, e -> e.discardChannel(simpleChannel))
.get();
...
#Autowired
#Qualifier("SIMPLE_CHANNEL")
private MessageChannel simpleChannel;
#Bean
public IntegrationFlow simpleFlow() {
return IntegrationFlows.from(simpleChannel)
.handle(m -> System.out.println("Hello world"))
.get();
#Bean(name = "SIMPLE_CHANNEL")
public MessageChannel simpleChannel() {
return new DirectChannel();
}
But if the discard channel is defined as name of the channel, everything works.
Debuging I found that mentioned above the part of the code:
IntegrationFlow integrationFlow = IntegrationFlows.from("channelName")
.filter(simpleMessageSelectorImpl, e -> e.discardChannel(simpleChannel))
.get();
returns flow object which has map with integrationComponents and one of the component which is FilterEndpointSpec has "handler" field of type MessageFilter with discardChannel = null, and discardChannelName = null;
But if discard channel is defined as name of the channel the mentioned field "handler" with discardChannel=null but discardChannelName="SIMPLE_CHANNEL", as result everything works good.
It is behavior of my running application. Also I wrote the test and in test everything works good for both cases (the test doesn't run all spring context so maybe it is related to any conflict there)
Maybe someone has idea what it can be.
The spring boot version is 2.1.8.RELEASE, spring integration is 5.1.7.RELEASE
Thanks

Answer 1

The behaviour you describe is indeed incorrect and made me wonder, but after testing it out I can't seem to reproduce it, so perhaps there is something missing from the information you provided. In any event, here is the complete app that I've modeled after yours which works as expected. So perhaps you can compare and see if something jumps:
#SpringBootApplication
public class IntegrationBootApp {
public static void main(String[] args) {
ApplicationContext context = SpringApplication.run(IntegrationBootApp.class, args);
MessageChannel channel = context.getBean("channelName", MessageChannel.class);
PollableChannel resultChannel = context.getBean("resultChannel", PollableChannel.class);
PollableChannel discardChannel = context.getBean("SIMPLE_CHANNEL", PollableChannel.class);
channel.send(MessageBuilder.withPayload("foo").build());
System.out.println("SUCCESS: " + resultChannel.receive());
channel.send(MessageBuilder.withPayload("bar").build());
System.out.println("DISCARD: " + discardChannel.receive());
}
#Autowired
#Qualifier("SIMPLE_CHANNEL")
private PollableChannel simpleChannel;
#Bean
public IntegrationFlow integrationFlow() {
IntegrationFlow integrationFlow = IntegrationFlows.from("channelName")
.filter(v -> v.equals("foo"), e -> e.discardChannel(simpleChannel))
.channel("resultChannel")
.get();
return integrationFlow;
}
#Bean(name = "SIMPLE_CHANNEL")
public PollableChannel simpleChannel() {
return new QueueChannel();
}
#Bean
public PollableChannel resultChannel() {
return new QueueChannel(10);
}
}
with output
SUCCESS: GenericMessage [payload=foo, headers={id=cf7e2ef1-e49d-1ecb-9c92-45224d0d91c1, timestamp=1576219339077}]
DISCARD: GenericMessage [payload=bar, headers={id=bf209500-c3cd-9a7c-0216-7d6f51cd5f40, timestamp=1576219339078}]