Retrieve multiple messages from SQS

Question

I have multiple messages in SQS. The following code always returns only one, even if there are dozens visible (not in flight). setMaxNumberOfMessages I th

Answer 1

For small task list I use FIFO queue like stackoverflow.com/a/55149351/13678017 for example modified AWS tutorial

            // Create a queue.
        System.out.println("Creating a new Amazon SQS FIFO queue called " + "MyFifoQueue.fifo.\n");
        final Map attributes = new HashMap<>();

        // A FIFO queue must have the FifoQueue attribute set to true.
        attributes.put("FifoQueue", "true");
        /*
         * If the user doesn't provide a MessageDeduplicationId, generate a
         * MessageDeduplicationId based on the content.
         */
        attributes.put("ContentBasedDeduplication", "true");
        // The FIFO queue name must end with the .fifo suffix.
        final CreateQueueRequest createQueueRequest = new CreateQueueRequest("MyFifoQueue4.fifo")
                        .withAttributes(attributes);
        final String myQueueUrl = sqs.createQueue(createQueueRequest).getQueueUrl();

        // List all queues.
        System.out.println("Listing all queues in your account.\n");
        for (final String queueUrl : sqs.listQueues().getQueueUrls()) {
            System.out.println("  QueueUrl: " + queueUrl);
        }
        System.out.println();

        // Send a message.
        System.out.println("Sending a message to MyQueue.\n");

        for (int i = 0; i < 4; i++) {

            var request = new SendMessageRequest()
                    .withQueueUrl(myQueueUrl)
                    .withMessageBody("message " + i)
                    .withMessageGroupId("userId1");
                    ;

            sqs.sendMessage(request);
        }

        for (int i = 0; i < 6; i++) {

            var request = new SendMessageRequest()
                    .withQueueUrl(myQueueUrl)
                    .withMessageBody("message " + i)
                    .withMessageGroupId("userId2");
                    ;

            sqs.sendMessage(request);
        }

        // Receive messages.
        System.out.println("Receiving messages from MyQueue.\n");
        var receiveMessageRequest = new ReceiveMessageRequest(myQueueUrl);

        receiveMessageRequest.setMaxNumberOfMessages(10);
        receiveMessageRequest.setWaitTimeSeconds(20);

        // what receive?
        receiveMessageRequest.withMessageAttributeNames("userId2");


        final List messages = sqs.receiveMessage(receiveMessageRequest).getMessages();
        for (final Message message : messages) {
            System.out.println("Message");
            System.out.println("  MessageId:     "
                    + message.getMessageId());
            System.out.println("  ReceiptHandle: "
                    + message.getReceiptHandle());
            System.out.println("  MD5OfBody:     "
                    + message.getMD5OfBody());
            System.out.println("  Body:          "
                    + message.getBody());
            for (final Entry entry : message.getAttributes()
                    .entrySet()) {
                System.out.println("Attribute");
                System.out.println("  Name:  " + entry
                        .getKey());
                System.out.println("  Value: " + entry
                        .getValue());
            }
        }