第三章 （6）Return消息机制

简介

• Return Listerner 用于处理一些不可路由的消息！
• 我们的消息生产者，通过制定一个Exchange和Routingkey，把消息送达到每一个队列中去，然后我们的消费者监听队列，进行消费处理操作！
• 但是在某些情况下，如果我们在发消息的时候，当前的exchange不存在或者制定的路由key路由不到，这个时候我们监听这种不可达的消息，就要用Return Listener!

关键属性

• Mandatory：如果为true，则监听器会接收到路由不可达的消息然后进行后续处理，如果未false，那么broker端自动删除该消息！

Return消息机制流程

代码实现

生产端

package club.yunqiang.rabbitmqapi.returnlistener;

import com.rabbitmq.client.*;

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

/**
 * @author 张云强
 * @date 2019/12/7
 */
public class Producer {

    public static void main(String[] args) throws IOException, TimeoutException {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");
        connectionFactory.setHost("localhost");

        Connection connection = connectionFactory.newConnection();

        Channel channel = connection.createChannel();

        String exchange = "test_return_exchange";
        String routingKey = "return.save";
        String routingKeyError = "abc.save";

        channel.addReturnListener(new ReturnListener() {
            @Override
            public void handleReturn(int replyCode, String replyText, String exchange, String routingKey, AMQP.BasicProperties properties, byte[] body) throws IOException {
                System.err.println("----- handle return -----");
                System.err.println("replyCode：" + replyCode);
                System.err.println("replyText：" + replyText);
                System.err.println("exchange：" + exchange);
                System.err.println("routingKey：" + routingKey);
                System.err.println("properties：" + properties);
                System.err.println("body：" + new String(body));
            }
        });

        String msg = "Hello Rabbit MQ Return Message";
        channel.basicPublish(exchange, routingKeyError, true, null, msg.getBytes());
    }

}

消费端

package club.yunqiang.rabbitmqapi.returnlistener;

import com.rabbitmq.client.*;

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

/**
 * @author 张云强
 * @date 2019/12/7
 */
public class Consumer {

    public static void main(String[] args) throws IOException, TimeoutException {
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setPort(5672);
        connectionFactory.setVirtualHost("/");
        connectionFactory.setHost("localhost");

        Connection connection = connectionFactory.newConnection();

        Channel channel = connection.createChannel();

        String exchangeName = "test_return_exchange";
        String routingKey = "return.#";
        String queueName = "test_return_queue";

        channel.exchangeDeclare(exchangeName, "topic", true, false, null);
        channel.queueDeclare(queueName, true, false, false, null);
        channel.queueBind(queueName, exchangeName, routingKey);

        DefaultConsumer consumer = new DefaultConsumer(channel){
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
                String msg = new String(body);
                System.out.println("消费端：" + msg);
            }
        };

        channel.basicConsume(queueName, true, consumer);
    }

}

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