Spring integration default output channel not working

Question

In my app I'm trying to route based on returned http status values from a service method, and the rest of http statuses are to be routed to a default error channel. But this default mapping is not working,

@Bean
public IntegrationFlow bridgeFlow() {
    return IntegrationFlows.from(ApplicationConfiguration.QUEUE_CHANNEL)
            .bridge(e -> e.poller(Pollers.fixedDelay(2500).maxMessagesPerPoll(MAX_MSG_PER_POLL)))
            .handle(someService, "someMethod")
            .route(router())                
            .get();
}

public ExpressionEvaluatingRouter router() {
    ExpressionEvaluatingRouter router = new ExpressionEvaluatingRouter("headers['httpStatus']");
    router.setChannelMapping("422", REJECTED_QUEUE_CHANNEL);
    router.setChannelMapping("202", "nullChannel");
    router.setChannelMapping("201", "nullChannel");
    router.setDefaultOutputChannelName(ORR_FAILED_QUEUE_CHANNEL);// When I receive other status codes it should go into this channel. But it's not going and throwing a runtime exception when a status code other than these is received.
    return router;
}

I tried putting the default channel after .route(router()).channel(ORR_FAILED_QUEUE_CHANNEL) and also as .route(router()).handle(ORR_FAILED_QUEUE_CHANNEL). But it failed during bean initialization saying The 'currentComponent' (org.springframework.integration.router.ExpressionEvaluatingRouter@1ca574db) is a one-way 'MessageHandler' and it isn't appropriate to configure 'outputChannel'. This is the end of the integration flow.

Answer 1

You are missing to set this option to false on the router:

/**
 * Specify whether this router should ignore any failure to resolve a channel name to
 * an actual MessageChannel instance when delegating to the ChannelResolver strategy.
 * @param resolutionRequired true if resolution is required.
 */
public void setResolutionRequired(boolean resolutionRequired) {

And there is a docs on the matter: https://docs.spring.io/spring-integration/docs/current/reference/html/message-routing.html#router-common-parameters