Spring Boot + RabbitMQ Tutorial - Configure Listeners to consume messages | JavaInUse

In a previous tutorial we had implemented a Spring Boot + RabbitMQ example to send publish message to RabbitMQ Queue. In this tutorial we will be implementing a Spring Boot + RabbitMQ example to consume message from a RabbitMQ Queue. In next tutorial we will be exploring the various RabbitMQ Exchange types and implementing them using Spring Boot.

RabbitMQ - Table Of Contents
What is Messaging?
Getting Started with RabbitMQ - Install and start RabbitMQ.
Spring Boot + RabbitMQ Publish Message Example
Spring Boot + RabbitMQ Tutorial - Configure Listeners to consume messages using MessageListenerContainer
Spring Boot + RabbitMQ Consume Message Example using RabbitListener
Spring Boot + RabbitMQ Tutorial - Implement Exchange Types
Spring Boot + RabbitMQ Tutorial - Retry and Error Handling Example
Spring Cloud Stream - RabbitMQ Publish Message Example
Spring Cloud Stream - RabbitMQ Consume Message Example
Pivotal Cloud Foundry Tutorial - Deploying Spring Boot + RabbitMQ Application to PCF 

Let's Begin

The Maven project will be as follows-

The pom.xml will have the following dependencies-

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.javainuse</groupId>
	<artifactId>spring-boot</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.1.RELEASE</version>
		<relativePath /> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<java.version>1.8</java.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-amqp</artifactId>
		</dependency>
	</dependencies>

</project>	 

We will first be creating a listener class which implements the AMQP MessageListener interface. This class is responsible for getting the message from the RabbitMQ queue.

package com.javainuse.service;

import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageListener;
import org.springframework.stereotype.Service;

@Service
public class RabbitMQListner implements MessageListener {

	public void onMessage(Message message) {
		System.out.println("Consuming Message - " + new String(message.getBody()));
	}

}

Next we will be creating the Spring Boot Configuration class for RabbitMQ. We will

• Create Queue bean using which we create a RabbitMQ named javainuse.input-queue. This will be a non durable queue. Do not misunderstand a non durable queue to be a temporary queue. Durability property is related to how long a message will be stored in the queue. For example for in RabbitMQ restart messages in non durable queue will be lost while those in durable queue will not be lost.
• Create MessageListenerContainer where we configure the RabbitMQConnections. Spring MessageListenerContainer is a replacement for a Message-Driven EJB. A connection is set up with the AMQ topic/queue, it gets messages from that topic/queue and feeds them to your MessageListener. We will be making use of the default connectionfactory. If we do not wish to use the default connectionfactory we can can create our own CachingConnectionFactory and use it.

package com.javainuse.config;

import org.springframework.amqp.core.Queue;
import org.springframework.amqp.rabbit.connection.CachingConnectionFactory;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.listener.MessageListenerContainer;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import com.javainuse.service.RabbitMQListner;

@Configuration
public class RabbitMQConfig {

	@Value("${javainuse.rabbitmq.queue}")
	String queueName;

	@Value("${spring.rabbitmq.username}")
	String username;

	@Value("${spring.rabbitmq.password}")
	private String password;

	@Bean
	Queue queue() {
		return new Queue(queueName, false);
	}
	
    //create MessageListenerContainer using default connection factory
	@Bean
	MessageListenerContainer messageListenerContainer(ConnectionFactory connectionFactory ) {
		SimpleMessageListenerContainer simpleMessageListenerContainer = new SimpleMessageListenerContainer();
		simpleMessageListenerContainer.setConnectionFactory(connectionFactory);
		simpleMessageListenerContainer.setQueues(queue());
		simpleMessageListenerContainer.setMessageListener(new RabbitMQListner());
		return simpleMessageListenerContainer;

	}
    
    //create custom connection factory
	/*@Bean
	ConnectionFactory connectionFactory() {
		CachingConnectionFactory cachingConnectionFactory = new CachingConnectionFactory("localhost");
		cachingConnectionFactory.setUsername(username);
		cachingConnectionFactory.setUsername(password);
		return cachingConnectionFactory;
	}*/
	
    //create MessageListenerContainer using custom connection factory
	/*@Bean
	MessageListenerContainer messageListenerContainer() {
		SimpleMessageListenerContainer simpleMessageListenerContainer = new SimpleMessageListenerContainer();
		simpleMessageListenerContainer.setConnectionFactory(connectionFactory());
		simpleMessageListenerContainer.setQueues(queue());
		simpleMessageListenerContainer.setMessageListener(new RabbitMQListner());
		return simpleMessageListenerContainer;

	}*/
	
}

In the application.properties define the following-

spring.rabbitmq.host=localhost
spring.rabbitmq.port=5672
spring.rabbitmq.username=guest
spring.rabbitmq.password=guest
javainuse.rabbitmq.queue=javainuse.input-queue

Finally create the bootstrap class which makes use of the SpringBootApplication Annotation

package com.javainuse;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringBootRabbitMQApplication {

	public static void main(String[] args) {
		SpringApplication.run(SpringBootRabbitMQApplication.class, args);
	}
}

In a previous tutorial we have shown how to install RabbitMQ and get started. Once you have followed implemented this tutorial go to localhost:15672

Use the username and password as guest.If we now go to the queues section, currently there are no queues

Start the Spring Boot Application. If we now again go to the RabbitMQ Management Console Queues section we can see that a queue named javainuse.input-queue has been created.

Now select the queue and publish a message.

If we now go to the eclipse console we can see that our application has consumed the RabbitMQ message and printed its content.

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Spring Boot + RabbitMQ Listeners to consume message