Spring Boot 2 - broadcast messages to each application instance using RabbitMQ

In this article, we would like to show you how to create Spring Boot 2 application that broadcasts messages to each application instance that uses RabbitMQ.

Spring Boot 2 Applications

In this section, we can find a simplified solution that realizes broadcasting.

Hint: the article extends project in this article.

Producer

ProducerConfig.java file:

package com.example.demo;

import org.springframework.amqp.core.FanoutExchange;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class ProducerConfig {

    @Bean
    public FanoutExchange broadcastExchange() {
        return new FanoutExchange("my-exchange");
    }
}

ProducerController.java file:

package com.example.demo;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

@Controller
public class ProducerController {

    @Autowired
    private ProducerService producerService;

    @RequestMapping("/test")
    @ResponseBody
    public void test() {
        this.producerService.broadcastMessage("Testing message...");
    }
}

ProducerService.java file:

package com.example.demo;

import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class ProducerService {

    @Autowired
    private RabbitTemplate template;

    public void broadcastMessage(String message) {
        this.template.convertAndSend("my-exchange", "", message);  // broadcasts string message to each my-queue-* via my-exchange
    }
}

Consumer

ConsumerConfig.java file:

package com.example.demo;

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.annotation.EnableRabbit;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.amqp.rabbit.listener.adapter.MessageListenerAdapter;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import java.util.UUID;

@Configuration
@EnableRabbit
public class ConsumerConfig {

    @Bean
    public String instanceId() {
        return "id-" + UUID.randomUUID();
    }

    @Bean
    public FanoutExchange broadcastExchange() {
        return new FanoutExchange("my-exchange");
    }

    @Bean
    public Queue instanceQueue(String instanceId) {
        return new Queue("my-queue-" + instanceId, true);
    }

    @Bean
    public Binding instanceBinding(Queue instanceQueue, FanoutExchange broadcastExchange) {
        return BindingBuilder.bind(instanceQueue).to(broadcastExchange);
    }

    @Bean
    public SimpleMessageListenerContainer container(String instanceId, ConnectionFactory connectionFactory, MessageListenerAdapter listenerAdapter) {
        SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        container.setQueueNames("my-queue-" + instanceId);
        container.setMessageListener(listenerAdapter);
        return container;
    }
}

ConsumerService.java file:

package com.example.demo;

import org.springframework.amqp.rabbit.listener.adapter.MessageListenerAdapter;
import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Service;

@Service
public class ConsumerService {

    @Bean
    public MessageListenerAdapter listenerAdapter(ConsumerService consumerService) {
        return new MessageListenerAdapter(consumerService, "handleMessage");
    }

    public void handleMessage(String message) {
        System.out.println("Message: " + message);
    }
}

References

1. Messaging with RabbitMQ - Spring Boot Docs

2. Fanout Exchange - RabbitMQ Docs