RabbitMQ: multiple messages and single consumer

Question

I have a problem with RabbitMQ consumer. Actually i have a single consumer geting messages from three queues. The problem is that i need to get a multiple messages from each of them, but my consumer gets only one per queue and ends getting. I would be grateful if someone could help me solve this problem.

Consumer code below

        for (int i = 0; i < queueNames.size(); i++) {

        Channel channel = connection.createChannel();
        QueueingConsumer consumer = new QueueingConsumer(channel);
        channel.basicConsume(queueNames.get(i).toString(), true, consumer_tag, consumer);

        flag = true;
        while (flag) {

            QueueingConsumer.Delivery delivery = consumer.nextDelivery();
            String routingKey = delivery.getEnvelope().getRoutingKey();
            System.out.println(routingKey);
            String message = new String(delivery.getBody(), "UTF-8");

                flag = false;
        }
    }

where queueNames is a list containing names of my queues (in number of 3).

Answer 1

You need to subscribe to the queue, a consumer will only consume 1 message the way you defined it

boolean autoAck = false;
channel.basicConsume(queueName, autoAck, "myConsumerTag",
 new DefaultConsumer(channel) {
     @Override
     public void handleDelivery(String consumerTag,
                                Envelope envelope,
                                AMQP.BasicProperties properties,
                                byte[] body)
         throws IOException
     {
         String routingKey = envelope.getRoutingKey();
         String contentType = properties.getContentType();
         long deliveryTag = envelope.getDeliveryTag();
         // (process the message components here ...)
         channel.basicAck(deliveryTag, false);
     }
 });

More info here: https://www.rabbitmq.com/api-guide.html

Answer 2

OK i solve the problem this way:

boolean flag;
    System.out.println("Rozmiar queue " + queueNames.size());
    for (int i = 0; i < queueNames.size(); i++) {

        Channel channel = connection.createChannel();
        QueueingConsumer consumer = new QueueingConsumer(channel);
        channel.basicConsume(queueNames.get(i).toString(), true, consumer_tag, consumer);

        flag = true;
        while (flag) {

            QueueingConsumer.Delivery delivery = consumer.nextDelivery(timeout);
            if (delivery == null) {
                flag = false;
            } else {

                String message = new String(delivery.getBody(), "UTF-8");
                System.out.println(" [x] Message Received '" + message + "'");
            }
        }
    }

I hope this solution could help someone in future :)