Starting with version 5.5, the ConsumerEndpointSpec provides a reactive() configuration property with an optional customizer Function<? super Flux<Message<?>>, ? extends Publisher<Message<?>>>. This option configures the target endpoint as a ReactiveStreamsConsumer instance, independently of the input channel type, which is converted to a Flux via IntegrationReactiveUtils.messageChannelToFlux(). The provided function is used from the Flux.transform() operator to customize (publishOn(), log(), doOnNext() etc.) a reactive stream source from the input channel.spring-doc.cn

The following example demonstrates how to change the publishing thread from the input channel independently of the final subscriber and producer to that DirectChannel:spring-doc.cn

@Bean
public IntegrationFlow reactiveEndpointFlow() {
    return IntegrationFlow
            .from("inputChannel")
            .transformWith(t -> t
                              .<String, Integer>transformer(Integer::parseInt)
                              .reactive(flux -> flux.publishOn(Schedulers.parallel()))
            )
            .get();
}

See Reactive Streams Support for more information.spring-doc.cn