Spring integration custom processing step

Question

I need to introduce processing step in spring integration something like that:

import org.springframework.messaging.Message;

public class SomeDocumentProcessingStep {

    public Message<MyDocument> process(Message<MyDocument> myMessage) {
        // do some manipulations with message like providing new headers;
        return resultingMessage;
    }
}

The question is how to include such processing step in spring integration configuration? I have something like that:

<int:chain input-channel="someInput" output-channel="someOutput">
    <!--Here I want to use my processing step class -->
    <!--Chain contains other processing steps like transformations -->
</int:chain>

One way on doing this if with service-activator , but then I need to send new message manually from my service. Something like this:

public class SomeService {
    private final MessageChannel outputChannel;
    private final MessagingTemplate template;
    // constructor ommited
    public void distribute(Message<MyDocument> message) {
        // do my manipulations
        template.send(outputChannel, resultingMessage);
    }
}

And configure it something like this:

<int:service-activator input-channel="someInput" ref="someService" method="distribute"/>

But I have a feeling that this is wrong approach. Is there a better way of doing that inside integration chain? I need this custom processing step that will be in the middle of processing of message. The usage of <int:header-enricher> is not sufficient for me as it only provide a way of creating headers one by one. I want to do it in one class.

Answer 1

You go right way with the <service-activator> inside chain . Only the problem you are facing that you don't need that channel on the service-activator . It is a chain - a single composite endpoint for a set of steps. So, you still have to send message somehow into that someInput , but that's already will be an entry point for the whole chain. Please, read docs on the matter: https://docs.spring.io/spring-integration/docs/5.0.4.RELEASE/reference/html/messaging-routing-chapter.html#chain