Spring Integration: copy one inbound message to multiple outbound

Question

I want to use Spring Integration to process MQTT messages.

This is my processing requirements: based on inbound message payload it should be copied to multiple messages with same payload but different headers. More specifically different MQTT topic header since I want to send them to different topics.

Also outbound messages should be sent in order: at first all transformed messages from the 1st inbound message, then all messages from the 2nd inbound messages etc.

What message endpoint(s) should I use to implement this?

Answer 1

So, what you're describing is actually not MQTT specific, rather an enterprise integration pattern called splitter and Spring Integration provides support for it which you can configure using XML, Annotation and/or Java DSL. You can find more info here.

In a nut shell Splitter is a Message Handler with a specific contract allowing it to return "many" from a "single" (kind of the reverse of aggregator). You basically receive a message (from MQTT in your case) and split it on multiple messages inside your splitter implementation.