This repository is a hands-on example of asynchronous messaging using Java, Spring Boot (Spring AMQP), and RabbitMQ. It demonstrates a typical event-driven pipeline:

Producer → Exchange → Queue → Consumer

The project includes a Docker Compose setup that starts RabbitMQ and runs the Spring Boot application using the Maven Wrapper.

AsynchronousMessaging/
├── assets/
│   └── rabbitmq-architecture.jpg    # Architecture diagram
├── src/
│   ├── main/
│   │   ├── java/                     # Source code (producer/consumer/config)
│   │   └── resources/                # Spring configuration
│   └── test/                         # Unit and integration tests
├── docker-compose.yml                # Docker setup
├── pom.xml                           # Maven dependencies
└── README.md                         # This file

• Java
• Spring Boot (Spring AMQP / RabbitMQ)
• RabbitMQ
• Maven (Maven Wrapper included)

• Publishing messages to RabbitMQ (producer)
• Consuming messages from RabbitMQ (consumer)
• Basic AMQP topology configuration (exchange / queue / binding)
• Running everything locally with Docker Compose

• Docker Engine + Docker Compose v2
• Linux is recommended for the provided Compose setup (see note below)

The included docker-compose.yml uses host networking as a workaround for some Docker/iptables configurations (where creating a Docker bridge network fails).

With host networking:

• containers share the host network stack
• ports are exposed directly on your machine
• ports: mappings are not required (and are ignored by Docker)

Make sure these ports are free on your host:

• RabbitMQ AMQP: 5672
• RabbitMQ Management UI: 15672
• Spring Boot app: 8080 (configurable)

From the repository root:

docker compose up

docker compose stop

docker compose down
RabbitMQ UI
URL: http://localhost:15672

username: guest

password: guest

The application connects to RabbitMQ using environment variables set in docker-compose.yml:

SPRING_RABBITMQ_HOST=localhost
SPRING_RABBITMQ_PORT=5672
SPRING_RABBITMQ_USERNAME=guest
SPRING_RABBITMQ_PASSWORD=guest

The app runs on:

SERVER_PORT=8080

To change it, update SERVER_PORT in docker-compose.yml.

The exact topology is defined in the application configuration and/or Spring AMQP config classes.

To find it, check:

• src/main/resources/application.yml or application.properties
• Configuration classes under src/main/java/... (often named *Rabbit*Config / *Amqp*Config)

Once verified, document the values here:

• Exchange: YOUR_EXCHANGE_NAME
• Queue: YOUR_QUEUE_NAME
• Routing key: YOUR_ROUTING_KEY

How you publish depends on how the producer is implemented:

• REST endpoint (@RestController)
• Startup runner (CommandLineRunner)
• Service method invoked internally

Locate your controller in src/main/java/... and adjust the URL accordingly.

Example request template:

curl -X POST "http://localhost:8080/api/messages" \
  -H "Content-Type: application/json" \
  -d '{"message":"hello rabbit","timestamp":"2026-01-31T12:00:00Z"}'

docker logs -f asyncmsg-app

docker logs -f asyncmsg-rabbitmq

Because host networking exposes ports on the host, you can get conflicts.

Check port usage:

sudo ss -lntp | egrep ':(5672|15672|8080)\b'

Fix:

• Stop the service using the port, or
• Change SERVER_PORT in docker-compose.yml

docker ps
docker logs -f asyncmsg-rabbitmq

• Ensure RabbitMQ is healthy (Compose defines a healthcheck)
• Verify RabbitMQ is listening on 5672
• Check app logs:

  docker logs -f asyncmsg-app

If you run RabbitMQ separately (local install or your own container), you can run the app directly.

./mvnw spring-boot:run

mvnw.cmd spring-boot:run

• src/main/java – Source code (producer/consumer/config)
• src/main/resources – Spring configuration
• pom.xml – Maven dependencies