Companion code for the messaging series on ankurm.com. Each directory is a self-contained Maven project for one article, with its own pom.xml, its own numbered documentation chapters, and its own captured output under docs/output/ — regenerated by that module's scripts/run-all.sh, never typed by hand.

Module	Article	What it demonstrates
`kafka-basics/`	Spring Boot 4.1 and Apache Kafka: Producer, Consumer and Serialisation from Scratch	The on-ramp: what the starter gives you, the two Jackson serializer families, where a key lands and why, and which defaults are Kafka's rather than Spring's
`rabbitmq/`	Spring Boot and RabbitMQ: Exchanges, Queues, Bindings and a Working Dead-Letter Queue	All four exchange types against a real broker, manual acknowledgement, and a dead-letter path exercised through both rejection and TTL expiry

The two brokers make an instructive pair. Kafka's consumer holds an offset and the broker remembers nothing about individual records; RabbitMQ's broker owns the message until it is acknowledged and can route, expire and dead-letter it on its own. Almost every difference in how you handle failure follows from that one sentence — which is why Kafka needs a retry topic to do what RabbitMQ does with a queue argument.

They are meant to be read in order. kafka-basics establishes that the default acknowledgement mode is BATCH and therefore that delivery is at-least-once; everything the error-handling module does exists because of that one sentence.

Common ground

All modules target the same verified stack: JDK 25 (Temurin 25.0.4.1+1), Spring Boot 4.1.1, Spring Framework 7.0.9. Versions were read from maven-metadata.xml on Maven Central and from Boot's own spring-boot-dependencies POM, rather than from release announcements.

Every module runs its broker without Docker, so the transcripts can be regenerated on any machine with a JDK: Kafka via the in-process KRaft broker in spring-kafka-test, RabbitMQ via a real broker started by the module's own scripts. Each module also ships a Testcontainers configuration for the cases where the deployed image is what you need to test against.

Licence

MIT — see LICENSE.