10、RabbitMQ教程-消息的两种消费模式

消费模式

RabbitMQ消费模式有两种，一种是队列的push，另外一个是从队列pull。对应API如下。

• pull: com.rabbitmq.client.Channel#basicGet。消息中间件主动将消息推送给消费者
• push: com.rabbitmq.client.Channel#basicConsume。消费者主动从消息中间件拉取消息

两种模式的区别

• push:推模式接收消息是最有效的一种消息处理方式。当我们使用该模式的时候，我们的消费端，只需要启动了之后，就会相当于使用了订阅模式，只要生产端不断推送消息，消费端就会持续接收到消息。
• pull:拉模式接收消息和push是完全不同的，它每次接收消息都需要去拉取一下队列的信息。由于是拉取的，实时性较差。不能及时有效的获取最新的消息，所以相对来说使用并不是很多。但是该模式对于部分业务量很小的功能来说确实一个不错的选择，能有效的降低对内存的消耗。

push模式的实例

import com.rabbitmq.client.*;
import lombok.SneakyThrows;

import java.io.IOException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * @author echo
 * @date 2021-01-14 15:05
 */
public class TopicConsumerTest {

    private static final String EXCHANGE_NAME = "exchange_topic";
    private static final String QUEUE_NAME = "queue_topic1";
    private static final String IP_ADDRESS = "192.168.230.131";
    private static final int PORT = 5672;

    public static void main(String[] args) throws IOException, TimeoutException, InterruptedException {

        ConnectionFactory factory = new ConnectionFactory();
        // 设置RabbitMQ的链接参数
        factory.setUsername("echo");
        factory.setPassword("123456");
        factory.setPort(PORT);
        factory.setHost(IP_ADDRESS);

        // 和RabbitMQ建立一个链接
        Connection connection = factory.newConnection();
        final Channel channel = connection.createChannel();
        //声明交换机 Fanout模式
        channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.TOPIC, true, false, null);
        //进行绑定，指定消费那个队列
        channel.queueBind(QUEUE_NAME, EXCHANGE_NAME, "", null);
        Consumer consumer = new DefaultConsumer(channel) {
            @SneakyThrows
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) {
                System.out.println("recv message: " + new String(body));
                try {
                    TimeUnit.SECONDS.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                channel.basicAck(envelope.getDeliveryTag(), false);
            }
        };
        channel.basicConsume(QUEUE_NAME, consumer);
        //等待回调函数执行完毕之后 关闭资源
        TimeUnit.SECONDS.sleep(5);
        channel.close();
        connection.close();
    }

}

pull模式实例

import com.rabbitmq.client.*;

import java.io.IOException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * @author echo
 * @date 2021-01-14 15:05
 */
public class TopicConsumerTest {

    private static final String EXCHANGE_NAME = "exchange_topic";
    private static final String QUEUE_NAME = "queue_topic1";
    private static final String IP_ADDRESS = "192.168.230.131";
    private static final int PORT = 5672;

    public static void main(String[] args) throws IOException, TimeoutException, InterruptedException {

        ConnectionFactory factory = new ConnectionFactory();
        // 设置RabbitMQ的链接参数
        factory.setUsername("echo");
        factory.setPassword("123456");
        factory.setPort(PORT);
        factory.setHost(IP_ADDRESS);

        // 和RabbitMQ建立一个链接
        Connection connection = factory.newConnection();
        final Channel channel = connection.createChannel();
        //声明交换机 Fanout模式
        channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.TOPIC, true, false, null);
        //进行绑定，指定消费那个队列
        channel.queueBind(QUEUE_NAME, EXCHANGE_NAME, "", null);
        GetResponse getResponse = channel.basicGet(QUEUE_NAME, false);
        System.out.println(new String(getResponse.getBody()));
        //等待回调函数执行完毕之后 关闭资源
        TimeUnit.SECONDS.sleep(5);
        channel.close();
        connection.close();
    }

}