RabbitMQ高级特性-生产端Return返回消息机制

为什么需要Return

Return Listener用于处理一些不可路由的消息

生产者通过指定Exchange和RoutingKey将消息发送达指定队列，消费者只需监听这个队列，进行消费操作。

但是在某些情况下，我们在发送消息的时候，当前Exchange不存在或者指定的路由key路由不到，这个时候我们如果需要监听这种达不到的消息，我们就需要使用Return Listener。

实现

流程图：

在API中配置项：

Mandatory：如果为true，则会监听路由不可达消息，然后进行后续处理；如果为false，那么broker自动删除这条消息。

代码实现

Producer

package com.wyg.rabbitmq.javaclient.producer_return;

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

import com.rabbitmq.client.*;

/**
 * 生产端return机制
 * 
 * @author [e-mail]
 * @date 2019-11-22 13:25
 * @since JDK1.8
 * @version V1.0
 */

public class Producer {
    private static final String HOST = "localhost";
    private static final int PORT = 5672;
    private static final String USERNAME = "guset";
    private static final String PASSWORD = "guset";

    public static void main(String[] args) throws IOException, TimeoutException {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost(HOST);
        factory.setVirtualHost("/");
        factory.setPort(PORT);
        factory.setUsername(USERNAME);
        factory.setPassword(PASSWORD);
        Connection connection = factory.newConnection();

        Channel channel = connection.createChannel();
        String exchangeName = "test_return_exchange";
        String routingKey = "return.ok";
        String routingKeyError = "return.error";
        // 申明exchange
        channel.exchangeDeclare(exchangeName, "topic");
        // 添加监听
        channel.addReturnListener(new ReturnListener() {
            @Override
            public void handleReturn(int replyCode, String replyText, String exchange, String routingKey,
                AMQP.BasicProperties properties, byte[] body) throws IOException {
                System.out.println("---生产端---");
                System.out.println("replyCode:" + replyCode);
                System.out.println("replyText:" + replyText);
                System.out.println("exchange:" + exchange);
                System.out.println("routingKey:" + routingKey);
                System.out.println("properties:" + properties);
                System.out.println("body:" + new String(body));

            }
        });

        // 设置 mandatory 为 true
        boolean mandatory = true;
        String msg = "这是一条return确认消息1,routingKey " + routingKey;
        channel.basicPublish(exchangeName, routingKey, mandatory, null, msg.getBytes("UTF-8"));
        String msg2 = "这是一条return确认消息2,routingKey " + routingKeyError;
        channel.basicPublish(exchangeName, routingKeyError, mandatory, null, msg2.getBytes("UTF-8"));

    }

    // 注意，因为要等待broker的return消息，暂时不关闭channel和connection
}

Conusumer

package com.wyg.rabbitmq.javaclient.producer_return;

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

import com.rabbitmq.client.*;

/**
 * 生产端return机制
 * 
 * @author [e-mail]
 * @date 2019-11-22 14:07
 * @since JDK1.8
 * @version V1.0
 */

public class Consumer {

    private static final String HOST = "localhost";
    private static final int PORT = 5672;
    private static final String USERNAME = "guset";
    private static final String PASSWORD = "guset";

    public static void main(String[] args) throws IOException, TimeoutException {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost(HOST);
        factory.setVirtualHost("/");
        factory.setPort(PORT);
        factory.setUsername(USERNAME);
        factory.setPassword(PASSWORD);
        Connection connection = factory.newConnection();

        Channel channel = connection.createChannel();

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

        // 申明exchange
        channel.exchangeDeclare(exchangeName, "topic");
        // 申明队列
        channel.queueDeclare(queueName, true, false, false, null);
        // 队列绑定到exchange
        channel.queueBind(queueName, exchangeName, routingKey, null);

        DeliverCallback deliverCallback = new DeliverCallback() {
            @Override
            public void handle(String consumerTag, Delivery message) throws IOException {
                try {
                    System.out.println("---消费者---：" + new String(message.getBody(), "UTF-8"));
                } finally {
                    // consumer手动 ack 给broker
                    channel.basicAck(message.getEnvelope().getDeliveryTag(), false);
                }
            }
        };
        CancelCallback cancelCallback = new CancelCallback() {
            @Override
            public void handle(String consumerTag) throws IOException {
                System.out.println("---消费者：cancelCallback");
            }
        };

        // 消费消息
        channel.basicConsume(queueName, false, deliverCallback, cancelCallback);
    }
}

注意

先运行Consumer,绑定正确的exchange和routingKey,再启动生产者

运行结果

Consumer

Producer，其中routingKey 为 return.error的消息无法路由，被Return Listener监听到