如何消费一条消息？

Question

在rabbitmq中使用example，消费者一次从队列中获取所有消息。如何消费一条消息退出？

QueueingConsumer consumer = new QueueingConsumer(channel);
channel.basicConsume(QUEUE_NAME, true, consumer);

while (true) {
  QueueingConsumer.Delivery delivery = consumer.nextDelivery();
  String message = new String(delivery.getBody());
  System.out.println(" [x] Received '" + message + "'");
}

Answer 1

您必须声明 basicQos 设置以一次获取一条从 ACK 到 NACK 状态的消息，并禁用自动 ACK 以明确给出确认。

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);
        }
    }

希望对您有所帮助！

Answer 2

使用 AMQP 0.9.1 basic.get 同步获取一条消息。

ConnectionFactory factory = new ConnectionFactory();
factory.setUri(uri);

Connection connection = factory.newConnection();
Channel channel = connection.createChannel();

channel.queueDeclare(QUEUE_NAME, true, false, false, null);

GetResponse response = channel.basicGet(QUEUE_NAME, true);
if (response != null) {
    String message = new String(response.getBody(), "UTF-8");
}

channel.close();
connection.close();

Answer 3

const consumeFromQueue = async (queueName) => {
    try {

        let data = await channel.get(queueName)// get one msg at a time
        if (data) {

            data.content ? eval("(" + data.content.toString() + ")()") : ""
            channel.ack(data)
        } else {
            //console.log("Empty Queue")
        }
    }
    catch (error) {
        //console.log("Error while consuming from rabbitmq queue", error)
        return Promise.reject(error)
    }
}

如何消费一条消息？

How to consume one message?

java

rabbitmq