如何消费一条消息？

您必须声明basicQos设置，才能一次从ACK到NACK状态获取一条消息，并禁用自动ACK以便显式给出确认。

ConnectionFactory factory = new ConnectionFactory();    factory.setHost("localhost");    Connection connection = factory.newConnection();    Channel channel = connection.createChannel();    channel.basicQos(1);    channel.queueDeclare(QUEUE_NAME, true, false, false, null);    System.out.println("[*] waiting for messages. To exit press CTRL+C");    QueueingConsumer consumer = new QueueingConsumer(channel);    channel.basicConsume(QUEUE_NAME, consumer);    while(true) {        QueueingConsumer.Delivery delivery = consumer.nextDelivery();        int n = channel.queueDeclarePassive(QUEUE_NAME).getMessageCount();        System.out.println(n);        if(delivery != null) { byte[] bs = delivery.getBody(); System.out.println(new String(bs)); //String message= new String(delivery.getBody()); channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false); //System.out.println("[x] Received '"+message);        }    }

希望能帮助到你！