Spring Boot RabbitMQ Fanout Exchange Example

In this tutorial, we’ll go through the step by step guide to implement messaging using RabbitMQ in a Spring Boot Application and will see how to publish and consume messages to Fanout Exchange and queues using RabbitMQ.

This is the third blog post in this series.

First part covers about Direct Exchange example

Second part covers about Topic Exchange Example

Fanout Exchange Example

When the producer publishes messages to RabbitMQ server , they are not published directly to a queue, instead first they goes to exchange. An exchange is in charge of routing messages to different queues using bindings and routing keys. A binding connects a queue and an exchange.

There are 5 types of exchanges

  • Direct Exchange
  • Topic Exchange
  • Fanout Exchange
  • Headers Exchange
  • Default Exchange

In this blog post I will show you how to create and use Fanout Exchange in Spring Boot applications.

Fanout Exchange

A fanout exchange copies and routes a received message to all queues that are bound to it regardless of routing keys or pattern matching . The keys provided will simply be ignored.

Fanout exchanges can be useful when the same message needs to be sent to one or more queues with consumers who may process the same message in different ways.

The above image (Fanout Exchange) shows an example where a message received by the exchange is copied and routed to all three queues bound to the exchange. It could be political ,sports or weather updates that should be sent out to each connected

In above RabbitMQ setup ,

  • a message reached to fanout exchange will be delivered to all the connected queues

Setting Up Project

Go to Spring Initializr and add the following starter dependencies to a project.

  • Spring Web
  • Spring for RabbitMQ

Change the Name to “springboot-rabbitmq-producer” and then click on “Generate” button. A .zip will download. Unzip it. Inside you’ll find a simple, Maven-based project including a pom.xml build file (NOTE: You can use Gradle. The examples in this tutorial will be Maven-based.)

Import the project to your favorite IDE.

Configuring RabbitMQ connection

To integrate RabbitMQ in your Spring-powered web applications, all you need to do is configure Spring to use RabbitMQ. Spring for RabbitMQ provides a convenient class called RabbitTemplate to send and receive messages

By default RabbitTemplate class uses following configuration to connect to RabbitMQ instance.

host: localhost

port: 5672

username: guest

password: guest

Using application.properties

You can also configure connection to RabbitMQ instance using application.properties.

In real world application you need configure using application properties only.

spring.rabbitmq.host=localhost spring.rabbitmq.port=5672 (non-SSL) or 5671 (SSL) spring.rabbitmq.username=guest spring.rabbitmq.password=guest
Code language: plaintext (plaintext)

Let’s see how to setup the Fanout exchange ,queues and bindings programmatically in Spring Boot application.

We create a configuration class to create exchange ,queues and bindings

package dev.fullstackcode.sb.rabbitmq.producer.config; import org.springframework.amqp.core.Binding; import org.springframework.amqp.core.BindingBuilder; import org.springframework.amqp.core.FanoutExchange; import org.springframework.amqp.core.Queue; import org.springframework.amqp.rabbit.connection.ConnectionFactory; import org.springframework.amqp.rabbit.core.RabbitTemplate; import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter; import org.springframework.amqp.support.converter.MessageConverter; import org.springframework.boot.ApplicationRunner; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class RabbitMQConfiguration { @Bean Queue queueA() { return new Queue("queue.A", false); } @Bean Queue queueB() { return new Queue("queue.B", false); } @Bean Queue queueC() { return new Queue("queue.C", false); } @Bean FanoutExchange exchange() { return new FanoutExchange("exchange.fanout"); } @Bean Binding bindingA(Queue queueA, FanoutExchange exchange) { return BindingBuilder.bind(queueA).to(exchange); } @Bean Binding bindingB(Queue queueB, FanoutExchange exchange) { return BindingBuilder.bind(queueB).to(exchange); } @Bean Binding bindingC(Queue queueC, FanoutExchange exchange) { return BindingBuilder.bind(queueC).to(exchange); } @Bean ApplicationRunner runner(ConnectionFactory cf) { return args -> cf.createConnection().close(); } @Bean MessageConverter messageConverter() { return new Jackson2JsonMessageConverter(); } @Bean RabbitTemplate rabbitTemplate(ConnectionFactory connectionFactory) { RabbitTemplate rabbitTemplate = new RabbitTemplate(connectionFactory); rabbitTemplate.setMessageConverter(messageConverter()); return rabbitTemplate; } }
Code language: Java (java)

Queue – beans are used to create queue

FanoutExchange – beans are used to create Fanout exchange

Binding – beans are used to create bindings between exchange and Queue.

MessageConverter – is used to convert object to Json format

RabbitTemplate – is used to configure the RabbitTemplate.

In above config class , you can observe that there is no binding keys on when queues and exchanges

Note

By default RabbitTemplate uses SimpleMessageConverter class. SimpleMessageConverter class can be used to send data in string and byte format. You can also use SimpleMessageConverter to send json data but using Jackson2JsonMessageConverter class simplifies the work

Creating Exchange and Queues on Startup

Spring Boot application connects to RabbitMQ server instance and creates Exchange and Queues when first message is published . If you want your application to create Exchange and Queues on application startup , you should use following method.

@Bean ApplicationRunner runner(ConnectionFactory cf) { return args -> cf.createConnection().close(); }
Code language: Java (java)

Publishing Messages

Once RabbitTemplate is configured , it is very easy publish messages. We can use overloaded send/convertAndSend method to publish messages.

Let’s develop a controller class which publishes messages.

package dev.fullstackcode.sb.rabbitmq.producer.controller; import dev.fullstackcode.sb.rabbitmq.producer.model.Event; import org.springframework.amqp.core.FanoutExchange; import org.springframework.amqp.rabbit.core.RabbitTemplate; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RequestBody; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RestController; @RestController @RequestMapping(value ="rabbitmq/event") public class RabbitMQProducerController { @Autowired private RabbitTemplate rabbitTemplate; @Autowired private FanoutExchange fanoutExchange; @PostMapping public String send(@RequestBody Event event) { rabbitTemplate.convertAndSend(fanoutExchange.getName(), "", event); return "message sent successfully"; } }
Code language: Java (java)

Starting the RabbitMQ

Let’s use following docker compose file for starting RabbitMQ server in local development for our testing.

version: '3' services: rabbitmq: container_name: rabbitmq hostname: my-rabbitmq image: rabbitmq:3.10.6-management-alpine ports: - '5672:5672' - '15672:15672'
Code language: Java (java)
docker-compose up
Code language: plaintext (plaintext)

Starting Spring Boot RabbitMQ producer Application

Let’s start the springboot-raabitmq-producer application and publish some messages.

As we are connecting to RabbitMQ server on startup, it should create Fanout Exchange and Queues and bindings in RabbitMQ instance.

We can check this by going to management console of RabbitMQ. It is available at

http://localhost:15672

username/password -> guest/guest

Below images confirm that exchange, queue and bindings created successfully on startup.

Publishing Messages

Let’s publish messages by sending request to controller class.

Let’s look at the management console.

Now each queue has two messages as all messages are sent to all the queues

Consuming Messages

Now let’s develop a consumer application which consumes messages from RabbitMQ server.

First define MessageConverter to Convert Json String back to Object

package com.fullstackcode.sb.rabbitmq.consumer.config; import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter; import org.springframework.amqp.support.converter.MessageConverter; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class RabbitMQConfiguration { @Bean MessageConverter messageConverter() { return new Jackson2JsonMessageConverter(); } }
Code language: Java (java)

@RabbitListener annotation is used to receive messages from RabbitMQ queues.

Spring Boot will take care of converting message to corresponding Object

package com.fullstackcode.sb.rabbitmq.consumer.listener; import com.fullstackcode.sb.rabbitmq.consumer.model.Event; import lombok.extern.slf4j.Slf4j; import org.springframework.amqp.rabbit.annotation.RabbitListener; import org.springframework.amqp.rabbit.core.RabbitTemplate; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Component; @Component @Slf4j public class RabbitMQConsummer { @RabbitListener(queues = "queue.A") private void receiveQueueA(Event event) { log.info("Event received from queue A -> {}",event.toString()); } @RabbitListener(queues = "queue.B") private void receiveQueueB(Event event) { log.info("Event received from queue B -> {}",event); } @RabbitListener(queues = "queue.C") private void receiveQueueC(Event event) { log.info("Event received from queue C -> {}",event); } }
Code language: Java (java)

If you want to configure server properties using application.properties

spring.rabbitmq.host=localhost spring.rabbitmq.port=5672 (non-SSL) or 5671 (SSL) spring.rabbitmq.username=guest spring.rabbitmq.password=guest server.port=8081
Code language: plaintext (plaintext)

Once we start the consumer application, we can see following output.

INFO : Event received from queue A -> Event(id=1, name=Event A) INFO : Event received from queue C -> Event(id=1, name=Event A) INFO : Event received from queue B -> Event(id=1, name=Event A) INFO : Event received from queue A -> Event(id=2, name=Event B) INFO : Event received from queue C -> Event(id=2, name=Event B) INFO : Event received from queue B -> Event(id=2, name=Event B)
Code language: Java (java)

Connecting to Remote Host

The above consumer example connects to RabbitMQ instance running in local

If you want to connect to instance running on server, you need specify the server address in application.properties

You can configureaddress like below

For SSL connection

spring.rabbitmq.addresses=amqps://<username>:<password>@<host>/<virtual-host>
Code language: Java (java)

For non-SSL connection

spring.rabbitmq.addresses=amqp://<username>:<password>@<host>/<virtual-host>
Code language: Java (java)

If you prefer individual properties, you can also configure like below

spring.rabbitmq.host=<host> spring.rabbitmq.virtual-host=<virtaul-host> spring.rabbitmq.port=5671 (SSL) or 5672 ( non - SSL) spring.rabbitmq.username=<username> spring.rabbitmq.password=<password>
Code language: Java (java)

Note

RabbitMQ in general listens on port 5672. If RabbitMQ instance is running on SSL, it will listen on port 5671

Code language: Java (java)

You can download the source code from GitHub for this blog

producer – sureshgadupu/sb-rabbitmq-fanoutexchange (github.com)

consumer – sureshgadupu/sb-rabbitmq-fanoutexchange-consumer (github.com)

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