Spring Boot RabbitMQ Default Exchange Example

In this tutorial, we’ll examine how to integrate RabbitMQ with Spring Boot applications to send and receive messages using the Default Exchange.

This is the fourth post in this series.

First part covers about Direct Exchange

Second part covers about Topic Exchange

Third part covers about Fanout Exchange

Fourth part covers about Headers Exchange

Default exchange

The default exchange is a pre-declared direct exchange with no name, usually referred by an empty string. When you use default exchange, your message is delivered to the queue with a name equal to the routing key of the message. Every queue is automatically bound to the default exchange with a routing key which is the same as the queue name.

If message with routing key Queue.A is it is sent to Queue.A

If message with routing key Queue.B is it is sent to Queue.B

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 queues and bindings programmatically in Spring Boot application.

Default exchange pre declared exchange provided by RabbitMQ server. So no need to create it.

We create a configuration class to create queues

package dev.fullstackcode.sb.rabbitmq.producer.config; 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 MessageConverter messageConverter() { return new Jackson2JsonMessageConverter(); } @Bean ApplicationRunner runner(ConnectionFactory cf) { return args -> cf.createConnection().close(); } @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

MessageConverter – is used to convert object to Json format

RabbitTemplate – is used to configure the RabbitMQ server.

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

When working with Default Queue, we do not declare any exchange and bindings as it is pre declared in RabbitMQ server and bindings are based on the queue names

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 Queues on Startup

Spring Boot application connects to RabbitMQ server instance and creates Queues when first message is published . If you want your application to create 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 on RabbitTemplate class to publish messages.

Let’s develop a controller class which publishes messages.

package dev.fullstackcode.sb.rabbitmq.producer.controller; import com.fasterxml.jackson.core.JsonProcessingException; import com.fasterxml.jackson.databind.ObjectMapper; import dev.fullstackcode.sb.rabbitmq.producer.model.Event; import org.springframework.amqp.core.DirectExchange; import org.springframework.amqp.core.FanoutExchange; import org.springframework.amqp.core.HeadersExchange; import org.springframework.amqp.core.Message; import org.springframework.amqp.core.MessageProperties; import org.springframework.amqp.rabbit.core.RabbitAdmin; import org.springframework.amqp.rabbit.core.RabbitTemplate; import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter; import org.springframework.amqp.support.converter.MessageConverter; import org.springframework.amqp.support.converter.SimpleMessageConverter; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.HttpStatus; import org.springframework.messaging.MessageHeaders; import org.springframework.messaging.converter.JsonbMessageConverter; 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; import org.springframework.web.server.ResponseStatusException; import java.util.HashMap; import java.util.Map; @RestController @RequestMapping(value ="rabbitmq/event") public class RabbitMQProducerController { @Autowired private RabbitTemplate rabbitTemplate; @PostMapping public String send(@RequestBody Event event) { if( event.getName().equalsIgnoreCase("Event A")) { rabbitTemplate.convertAndSend("queue.A", event); } else if (event.getName().equalsIgnoreCase("Event B")) { rabbitTemplate.convertAndSend("queue.B", event); } else if (event.getName().equalsIgnoreCase("Event C")) { rabbitTemplate.convertAndSend("queue.C", event); } else { throw new ResponseStatusException(HttpStatus.BAD_REQUEST,"unknown 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 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 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.

Each queue has one message based on the queue name

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.stereotype.Component; @Component @Slf4j public class RabbitMQConsumer { @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)

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 B -> Event(id=2, name=Event B) INFO : Event received from queue C -> Event(id=3, name=Event C)
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

You can download source code from GitHub

Producer – sureshgadupu/sb-rabbitmq-defaultexchange (github.com)

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

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