Introduction for Spring + RabbitMQ:

This project is about to demonstrate using RabbitMQ with Springboot technologies.

• RabbitMQ : https://www.rabbitmq.com/
• Springboot : https://spring.io
• CloudAmqp : https://www.cloudamqp.com/docs/index.html
• Dzone : https://dzone.com/articles/spring-boot-rabbitmq-tutorial-retry-and-error-hand
• With NodeJS : https://medium.com/swlh/real-time-exchange-information-with-microservices-and-nodejs-e6bf6623bca6
• Initial Src : https://medium.com/@sopheamak/rabbitqm-with-springboot-fd085dcab484

When using RabbitMQ the publisher never directly sends a message to a queue. Instead, the publisher sends messages to an exchange. The Exchange is responsible for sending the message to an appropriate queue based on routing keys, bindings and header attributes. The Exchanges are the message routing agents which we can define and bindings are what connects the exchanges to the queues.

In the sample project, we will use the Queue and Exchange, and then bind them together.

There are 4 types of Exchanges in RabbitMQ-

• Direct Exchange
• Fanout Exchange
• Topic Exchange
• Header Exchange

REf: https://www.javainuse.com/messaging/rabbitmq/exchange

Prerequisites

These tutorials assume RabbitMQ is installed and running on localhost using the standard port (5672). In case you use a different host, port or credentials, connections settings would require adjusting.

Install RabbitMQ with docker

https://www.rabbitmq.com/download.html

docker run -it --rm --name rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:3-management

Usage

These tutorials use Maven. To build them run

mvn spring-boot:run

Direct Message

Based on the routing key, a message is sent to the queue having the same routing key specified in the binding rule. The routing key of exchange and the binding queue have to be an exact match. A message is sent to exactly one queue.

curl "http://localhost:8080/api/rabbitmq/producer?code=001&description=MyDescription"

Example

• Consumer : see class RabbitMQReciver.java
• Sender : see class RabbitMQSender.java

Fanout Exchange

The message is routed to all the available bounded queues. The routing key if provided is completely ignored. So this is a kind of publish-subscribe design pattern.

 curl -i "http://localhost:8080/api/rabbitmq/fanout?exchangeName=fanout-exchange&messageData=message`"

Topic Exchange

The Topic Exchange looks similar to Direct Message type, but the different is that the routing key of the exchange and the bound queues should not necessarily be an exact match. Using regular expressions like wildcard we can send the exchange to multiple bound queues.

   @Bean
    Binding allBinding(Queue allQueueTopic, TopicExchange topicExchange) {
        return BindingBuilder.bind(allQueueTopic).to(topicExchange).with("queue.*");
    }

curl "http://localhost:8080/api/rabbitmq/topic?exchangeName=topic-exchange&routingKey=queue.admin&messageData=MessageData"

Header Exchange

In this type of exchange the routing queue is selected based on the criteria specified in the headers instead of the routing key. This is similar to topic exchange type, but here we can specify complex criteria for selecting routing queues

curl "http://localhost:8080/api/rabbitmq/header?exchangeName=header-exchange&department=admin&messageData=MessageValue"