RabbitMQ how to return message from java consumer

Question

I'm working with RabbitMQ and Java. I have an executeLogin() method, which sends a message on a queue and wait a reply on another queue: if the returned message contains true in the isSuccess field, I need to return true to the caller of the executeLogin() method, if isSuccess is false, i need to return false (not logged). I tried this way:

boolean logged = false; 
Consumer consumer = new DefaultConsumer(channel) {
    @Override
    public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
        String message = new String(body, "UTF-8");
        LoginConfirmation confirm = gson.fromJson(message, LoginConfirmation.class);
        channel.queueDelete(reply_to);
        System.out.println(" [x] Received '" + message + "'");
        LOGGER.log(Level.FINE, gson.toJson(confirm));
        logged = confirm.isSuccess();
    }
};
channel.basicConsume(reply_to, true, consumer);

or this way:

GetResponse response = channel.basicGet(reply_to, false);
if(response == null){
    System.out.println("No message");
}else{
    byte[] body = response.getBody();
    String msg = new String(body, "UTF-8");
    System.out.println(msg);
}

But in both ways, I can't solve my problem: in the first way, it returns false, but it prints the message (with "isSuccess": true). In the second way, it prints "no message".

I think the problem is that basicConsume and defaultConsumer are asynchronous , so at the beginning it doesn't retrieve the message, but when it retrieves it, it prints it.

Answer 1

Yes, the communication is asynchronous.

In you case, I think, the RPC pattern is appropriate:

https://www.rabbitmq.com/tutorials/tutorial-six-java.html

But what if we need to run a function on a remote computer and wait for the result? Well, that's a different story. This pattern is commonly known as Remote Procedure Call or RPC.