Fanout——发布订阅模式，是一种广播机制。

此模式包括：一个生产者、一个交换机 (exchange)、多个队列、多个消费者。生产者将消息发送到交换机，交换机不存储消息，将消息存储到队列，消费者从队列中取消息。如果生产者将消息发送到没有绑定队列的交换机上，消息将丢失。

用 Java demo 实现此模式
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package com.tszr.fanout;

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

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

public class Productor {
    private static final String EXCHANGE_NAME = "fanout_exchange";

    public static void main(String[] args){
        // 1、创建连接工程
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("127.0.0.1");
        factory.setUsername("guest");
        factory.setPassword("guest");
        factory.setVirtualHost("/");

        Connection connection = null;
        Channel channel = null;
        try {
            // 2、获取连接、通道
            connection = factory.newConnection();
            channel = connection.createChannel();
            // 消息内容
            String message = "hello fanout mode";
            // 指定路由key
            String routeKey = "";
            String type = "fanout";
            // 3、声明交换机
            channel.exchangeDeclare(EXCHANGE_NAME, type);
            // 4、声明队列
            channel.queueDeclare("queue1", false, false, false, null);
            channel.queueDeclare("queue2", false, false, false, null);
            channel.queueDeclare("queue3", false, false, false, null);
            channel.queueDeclare("queue4", false, false, false, null);
            // 5、绑定 channel 与 queue
            channel.queueBind("queue1", EXCHANGE_NAME, routeKey);
            channel.queueBind("queue2", EXCHANGE_NAME, routeKey);
            channel.queueBind("queue3", EXCHANGE_NAME, routeKey);
            channel.queueBind("queue4", EXCHANGE_NAME, routeKey);
            // 6、发布消息
            channel.basicPublish(EXCHANGE_NAME, routeKey, null, message.getBytes("UTF-8"));
            System.out.println("消息发送成功!");
        } catch (IOException | TimeoutException e) {
            e.printStackTrace();
            System.out.println("消息发送异常");
        }finally {
            // 关闭通道
            if (channel != null && channel.isOpen()) {
                try {
                    channel.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            // 关闭连接
            if (connection != null && connection.isOpen()) {
                try {
                    connection.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }
}
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package com.tszr.fanout;

import com.rabbitmq.client.*;

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

public class Customer {
    private static Runnable runnable = new Runnable() {
        @Override
        public void run() {
            // 创建连接工厂
            ConnectionFactory factory = new ConnectionFactory();
            factory.setHost("127.0.0.1");
            factory.setUsername("guest");
            factory.setPassword("guest");
            factory.setVirtualHost("/");

            final String queueName = Thread.currentThread().getName();
            Connection connection = null;
            Channel channel = null;
            try {
                // 获取连接、通道
                connection = factory.newConnection();
                channel = connection.createChannel();

                Channel finalChannel = channel;
                finalChannel.basicConsume(queueName, true, new DeliverCallback() {
                    @Override
                    public void handle(String consumerTag, Delivery delivery) throws IOException {
                        System.out.println(delivery.getEnvelope().getDeliveryTag());
                        System.out.println(queueName + ":收到消息是：" + new String(delivery.getBody(), "UTF-8"));
                    }
                }, new CancelCallback() {
                    @Override
                    public void handle(String consumerTag) throws IOException {
                    }
                });
                System.out.println(queueName + ":开始接收消息");
            } catch (IOException |
                    TimeoutException e) {
                e.printStackTrace();
            } finally {
                // 关闭通道和连接......
            }
        }

    };

    public static void main(String[] args) throws IOException, TimeoutException {
        // 创建线程分别从四个队列中获取消息
        new Thread(runnable, "queue1").start();
        new Thread(runnable, "queue2").start();
        new Thread(runnable, "queue3").start();
        new Thread(runnable, "queue4").start();
    }
}
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