Question

说我有以下代码：

    final ReceiveMessageRequest receiveMessageRequest = new ReceiveMessageRequest(myQueueUrl);
    receiveMessageRequest.withMaxNumberOfMessages(10);
    final List<Message> 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<String, String> entry : message.getAttributes().entrySet()) {
            System.out.println("Attribute");
            System.out.println("  Name:  " + entry.getKey());
            System.out.println("  Value: " + entry.getValue());
        }
    }

根据我的理解，这段代码返回了10条消息。如果SQS队列中有1000条消息，那么我是否需要另一个循环？

有没有办法知道SQS队列大小？

Answer 1

是的，您将需要另一个（外部）循环来继续获取10个批次的消息，直到没有剩余消息为止。您不需要知道队列的大小，只需使用while循环并进行迭代，直到得到没有消息的响应为止。

类似这样的东西：

ReceiveMessageRequest receiveMessageRequest = new ReceiveMessageRequest(myQueueUrl);
receiveMessageRequest.withMaxNumberOfMessages(10);
List<Message> messages = sqs.receiveMessage(receiveMessageRequest).getMessages();
while (messages.size() > 0) {
    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<String, String> entry : message.getAttributes().entrySet()) {
            System.out.println("Attribute");
            System.out.println("  Name:  " + entry.getKey());
            System.out.println("  Value: " + entry.getValue());
        }
    }

    receiveMessageRequest = new ReceiveMessageRequest(myQueueUrl);
    receiveMessageRequest.withMaxNumberOfMessages(10);
    messages = sqs.receiveMessage(receiveMessageRequest).getMessages();
}

如果确实需要使消息数量仍在队列中，则可以向AWS开发工具包查询队列属性ApproximateNumberOfMessages。喜欢：

GetQueueAttributesResult attrResult = sqs.getQueueAttributes(queueUrl, ["ApproximateNumberOfMessages"]);
System.out.println("Messages in queue: " + attrResult.getAttributes()["ApproximateNumberOfMessages"]);

Answer 2

没有消息/空白消息可能会误导您。检索可能由于不同的原因而没有发生，例如：由于另一位消费者的投票，可见性超时 SQS基础架构的分布式性质

如何从SQS队列中获取所有消息，直到队列为空？

2 个答案: