如何从SQS队列获取所有消息,直到队列为空?

是的,您需要另一个(外部)循环来继续以10个为一批获取消息,直到没有消息留下。您不需要知道队列大小,只需使用while循环并迭代,直到得到没有消息的响应。

像这样:

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();
}

如果您确实需要获取仍在队列中的消息数,可以在AWS SDK中查询queue属性 ApproximateNumberOfMessages

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

没有消息/空消息可能是误导。检索可能由于不同的原因而没有发生,例如- 另一个使用者轮询导致可见性超时 SQS基础设施的分布式特性