I'm looking into spring integration, more specifically the Java DSL.

The DSL is presented by the IntegrationFlows factory for the IntegrationFlowBuilder. This produces the IntegrationFlow component, which should be registered as a Spring bean (by using the @Bean annotation). The builder pattern is used to express arbitrarily complex structures as a hierarchy of methods that can accept lambdas as arguments.

In my mind then, I define a configuration class with a @Bean.

    @Bean
    fun ftpInboundIntegrationFlow(ftpSf: DefaultFtpSessionFactory?): IntegrationFlow {
        val ftpSpecification = Ftp
            .inboundStreamingAdapter(template())
            .patternFilter("*.csv")
            .remoteDirectory(fromFolder)

        return IntegrationFlows
            .from(ftpSpecification) { pc: SourcePollingChannelAdapterSpec ->
                pc.poller { pm: PollerFactory ->
                    pm.cron(cronSyncExpression)
                }
            }
            .transform(StreamTransformer())
            .channel(doSomeBusinessLogic)
            .get()
    }

But I am rather confused how to, in my more specific service layer, handle this message.

I could, and it seems to work, create another @Bean in the service class.

    @Bean
    fun handleDoSomeBusinessLogicFlow(): IntegrationFlow {
        return IntegrationFlows.from("doSomeBusinessLogic")
            .handle { customers: List<SomeDomainModel>, headers: MessageHeaders ->
                //Some repository and service logic
            }
            .get()
    

I tried looking at examples (https://github.com/spring-projects/spring-integration-samples/tree/833f55d662fb17edda6bcb000d952a3d00aa1dd8). But almost all of them are just creating all the logic in the same place. It feels strange to define a @Bean in the @Service class.

CodePudding user response：

You are right: you can just have a business method in your service and use it from the .handle() instead of channel. You also can just use a @ServiceActivator on that method if you’d prefer loosely coupled distribution via channels. There is also an IntegrationFlowAdapter to have a service incapsulation, but still gain from flow definition.