Subscribe to RabbitMQ - Sample Code

Every queue within Rabbit MQ for issuers requires a subscription over the issuer's end to monitor the messages that get notified over the queue. Here is a simple Java-based Rabbit MQ subscription source code showing how simple it is to subscribe over a certain queue. Please refer Rabbit MQ Publish/Subscribe for additional details.

Java Rabbit MQ Subscription

Here is a sample code that when executed, pulls the available messages in the queue. Comments are added for code explanation.

Java

package com.essdocs.sample;

// Rabbit MQ Client Java based class
import com.rabbitmq.client.*;
import java.io.IOException;

public class AmqReceiver {

  // Setting up primary Rabbit MQ based details including Host Name, Virtual Host, Username, Password, Port and Queue name
	private final static String HOST_NAME = "${HOST_NAME}";
	private final static String VIRTUAL_HOST = "${VIRTUAL_HOST_UUID}";
	private final static String AMQ_USERNAME = "${USERNAME}";
	private final static String AMQ_PASSWORD = "${PASSWORD}";
	private final static int AMQ_PORT = ${HOST_NAME};//Usually 443 if SLL is used
	private final static String QUEUE_NAME = "${QUEUE_NAME}";

	public static void main(String[] args) {
		// Calling Recieve Message method with queue name as an argument
    receiveMessage(QUEUE_NAME);
	}
	public static void receiveMessage(String queueName) {
    
    // Creating ConnectionFactory and setting up Queue parameters within it
		ConnectionFactory factory = new ConnectionFactory();
		factory.setHost(HOST_NAME);
		factory.setVirtualHost(VIRTUAL_HOST);
		factory.setPort(AMQ_PORT);
		factory.setUsername(AMQ_USERNAME);
		factory.setPassword(AMQ_PASSWORD);
		try {
      // Indicates factory to be using SSL for secure data transmission
			factory.useSslProtocol();
		}
		catch (Exception e) {
			System.out.println("AWS MQ SSL connection error " + e.getMessage());
		}

		try {
			Connection connection = factory.newConnection();
			Channel channel = connection.createChannel();
      
      // Setting up queue object to the Channel Factory
			channel.queueDeclare(queueName, false, false, false, null);
			
      // AutoAck if set to false, will note remove the message from the queue after viewing
      boolean autoAck = false;
      
      // Retrieve MQ messages
			channel.basicConsume(queueName, autoAck, "myConsumerTag",
					new DefaultConsumer(channel) {
						@Override
						public void handleDelivery(String consumerTag,
												   Envelope envelope,
												   AMQP.BasicProperties properties,
												   byte[] body)
								throws IOException {
							long deliveryTag = envelope.getDeliveryTag();
              
              // Printing queue message over the console
							System.out.println("AWS MQ Received Message Body: " + new String(body));
							// (process the message components here ...)
							channel.basicAck(deliveryTag, false);
						}
					});
			channel.close();
			connection.close();
		}
		catch (Exception e) {
			System.out.println("Error when receiving the message : " + e.getMessage());
		}
	}
}

A successful execution of the above code snippet fetches the available messages from the queue and will display the messages in the queue. Here is how the output looks like.

📘

Additional Samples

Please refer https://www.rabbitmq.com/tutorials/tutorial-three-python.html for additional sample codes to subscribe to messages from the designated Rabbit MQs.