rabbitMQ basicQos和basicAck作用和关系

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.bs.utils.ConnectionUtil;
 
 
public class Producer {
    private final static String EXCHANGE_NAME = "direct_exchange";
 
    public static void main(String[] args) throws Exception {
        //1、获取连接
        Connection connection = ConnectionUtil.getConnection("localhost", 5672, "/", "guest", "guest");
        //2、声明信道
        Channel channel = connection.createChannel();
        //3、声明交换器，类型为direct
        channel.exchangeDeclare(EXCHANGE_NAME, "direct");
        //4、创建消息
        String message = "hello rabbitmq";
        //5、发布消息
        channel.basicPublish(EXCHANGE_NAME, "add", null, message.getBytes());
        System.out.println("生产者发送" + message + "'");
        //6、关闭通道
        channel.close();
        //7、关闭连接
        connection.close();
    }
}

消费者

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.QueueingConsumer;
import com.bs.utils.ConnectionUtil;
 
public class Consumer1 {
 
    private final static String QUEUE_NAME = "direct_queue_1";
 
    private final static String EXCHANGE_NAME = "direct_exchange";
 
    public static void main(String[] args) throws Exception{
        //1、获取连接
        Connection connection = ConnectionUtil.getConnection("localhost",5672,"/","guest","guest");
        //2、声明通道
        Channel channel = connection.createChannel();
        //3、声明队列
        channel.queueDeclare(QUEUE_NAME, false, false, false, null);
        //4、绑定队列到交换机，指定路由key为update
        channel.queueBind(QUEUE_NAME,EXCHANGE_NAME,"update");
        channel.queueBind(QUEUE_NAME,EXCHANGE_NAME,"delete");
        channel.queueBind(QUEUE_NAME,EXCHANGE_NAME,"add");
        //同一时刻服务器只会发送一条消息给消费者
        channel.basicQos(1);
        //5、定义队列的消费者
        QueueingConsumer queueingConsumer = new QueueingConsumer(channel);
        //6、监听队列,手动返回完成状态
        channel.basicConsume(QUEUE_NAME,false,queueingConsumer);
        //6、获取消息
        while (true){
            QueueingConsumer.Delivery delivery = queueingConsumer.nextDelivery();
            String message = new String(delivery.getBody());
            System.out.println(" 消费者1：" + message + "'");
            //消费者1接收一条消息后休眠10毫秒
            Thread.sleep(10);
            //返回确认状态
            channel.basicAck(delivery.getEnvelope().getDeliveryTag(),false);
        }
    }
 
}

RabbitMQ中的概念，channel.basicQos(1)指该消费者在接收到队列里的消息但没有返回确认结果之前,队列不会将新的消息分发给该消费者。队列中没有被消费的消息不会被删除，还是存在于队列中。

Prefetch count 和 basicQos中的参数一致（Prefetch count就是basicQos的参数值）

channel.basicQos(1);和channel.basicAck(delivery.getEnvelope().getDeliveryTag(),false);是配套使用，只有在channel.basicQos被使用的时候channel.basicAck(delivery.getEnvelope().getDeliveryTag(),false)才起到作用。