how to add all received messages of reply queue to List

Question

I am publishing messages to request queue and getting those messages in reply queue. Here i want to further process the all received messages, so i want to add all the messages to List before sending to my processor(To do further operations). Below is my code.

@Autowired
    private GeneralProcess generalProcess;

    List <RequestPojo> requestPojoGeneral = new ArrayList<RequestPojo>();

    @RabbitHandler
    @RabbitListener(containerFactory = "simpleMessageListenerContainerFactory", queues ="BulkSolve_GeneralrequestQueue")
    public void subscribeToRequestQueue(@Payload RequestPojo sampleRequestMessage, Message message) throws InterruptedException {


        requestPojoGeneral.add(sampleRequestMessage);
        System.out.println("List size issssss:" +requestPojoGeneral.size() );
        generalProcess.processRequestObjectslist(requestPojoGeneral);

        /*System.out.println("message in general listener is:" + sampleRequestMessage.getDistance());
        System.out.println("Message payload is:" + sampleRequestMessage);
        System.out.println("Message payload1111 is:" + message );*/

    }

The above code i am unable to get all messages at a time. I have to wait untill i get all the messages and populate list before calling generalProcess.processRequestObjectslist(requestPojoGeneral); .Can any one suggest best way to wait calling processor method until get all messages and add to list.

Thanks.

Answer 1

You can add a header to the messages eg messageCount .

Then

if ((int) message.getMessageProperties().getHeader("messageCount") == list.size() {
    process();
}

(Or some other technique such as adding a header "lastMessage=true").

Bear in mind, if your server crashes before you get the full list, you will lose messages unless you set the acknowledgeMode to MANUAL .

Then, after you have processed all the messages, call basicAck on the Channel for the last message.

You can get access to the Channel as a method parameter and the deliveryTag is in the MessageProperties .

The container prefetchCount must be at least as big as your biggest batch because the broker will only allow that number of not-ack'd messages outstanding.