在RabbitMQ中将“恒定”队列添加到主题交换

Question

I've recently learned RabbitMQ with hopes of implementing it in my work flow. (I will be implementing it in Java) I just finished all the tutorials and was curious how I would implement a "constant" queue instead of a "temporary" queue. Or at least allow the consumer to get the message that the exchange sent. For example if I send a topic of "kern.overflow" but a consumer is offline, as soon as my consumer comes online as long as it is listening for something related to "kern.#" or "#.overflow" I want it to receive un-received messages.

Answer 1

Here is the code to:

1. create a persistent queue
2. bind the queue to the topic with "kern.#" as routing-key:

code:

            String myPersistentQueue = "myPersistentQueue";
            boolean isDurable = true;
            boolean isExclusive = false;
            boolean isAutoDelete = false;
            channel.queueDeclare(myPersistentQueue, isDurable, isExclusive, isAutoDelete, null);
            channel.queueBind(myPersistentQueue, "myTopic", "kern.#");
            final QueueingConsumer consumer = new QueueingConsumer(channel);
            boolean autoAck = true;
            String tag1 = channel.basicConsume(myPersistentQueue, autoAck, consumer);
            executorService.execute(new Runnable() {
                @Override
                public void run() {
                    while (true) {
                        Delivery delivery;
                        try {
                            delivery = consumer.nextDelivery();
                            String message = new String(delivery.getBody());
                            System.out.println("Received: " + message);
                        } catch (Exception ex) {
                            Logger.getLogger(TestMng.class.getName()).log(Level.SEVERE, null, ex);
                        }
                    }
                }
            });
            System.out.println("Consumers Ready");

When you publish a message to myTopic using kern.overflow as routing-key the message is stored to the myPersistentQueue queue. The client can be off-line, when the client is on-line can get the messages.