Springboot 集成 RabbitMQ —— 发布订阅模式的广播实现

通过前面的学习，可以发现，消息都是通过交换器发送至队列的，一条消息只能被一个消费者处理，实际开发中还会有一种情况，就是一条消息需要被多个消费者处理，就是广播的形式；广播的模式需要使用到 FanoutExchange （散列交换器），FanoutExchange 会将消息发送至每一个与之绑定的队列中

FanoutExchange

代码主体没有太大的改动，增加了 FanoutExchange，并且将队列绑定至 FanoutExchange

截图中被标记的部分如下

@Configuration
public class MQTopicConfig {
    @Value("${spring.rabbitmq.host}")
    private String host;

    @Value("${spring.rabbitmq.port}")
    private int port;

    @Value("${spring.rabbitmq.username}")
    private String username;

    @Value("${spring.rabbitmq.password}")
    private String password;

    @Value("${spring.rabbitmq.publisher-returns}")
    private boolean publisherReturns;


    @Bean
    public ConnectionFactory connectionFactory() {
        CachingConnectionFactory connectionFactory = new CachingConnectionFactory(host,port);
        connectionFactory.setUsername(username);
        connectionFactory.setPassword(password);
        connectionFactory.setVirtualHost("/");
        connectionFactory.setPublisherReturns(publisherReturns);
        connectionFactory.setPublisherConfirms(true);
        return connectionFactory;
    }

    @Bean
    @Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
    //必须是prototype类型
    public RabbitTemplate rabbitTemplate() {
        RabbitTemplate template = new RabbitTemplate(connectionFactory());
        return template;
    }

    @Bean
    public Queue coreQueue() {
        return new Queue(Constant.HOSH_TOPIC);
    }

    @Bean
    public Queue subCoreQueue() {
        return new Queue(Constant.HOSH_TOPIC_NEW);
    }

    @Bean
    public TopicExchange coreTopicExchange() {
        return new TopicExchange(Constant.HOSH_TOPIC_EXC);
    }

    @Bean
    FanoutExchange fanoutExchange() {       // 广播交换器
        return new FanoutExchange(Constant.HOSH_BROADCAST_EXC);
    }

    @Bean
    public Binding bindingFanoutExchange() {    // coreQueue 队列绑定至广播交换器
        return BindingBuilder.bind(coreQueue()).to(fanoutExchange());
    }

    @Bean
    public Binding bindingSubFanoutExchange() {     // subCoreQueue 队列绑定至广播交换器
        return BindingBuilder.bind(subCoreQueue()).to(fanoutExchange());
    }

    @Bean
    public Binding bindingCoreExchange() {
        return BindingBuilder.bind(coreQueue()).to(coreTopicExchange()).with(Constant.HOSH_TOPIC);
    }

    @Bean
    public Binding bindingSubCoreExchange() {
        return BindingBuilder.bind(subCoreQueue()).to(coreTopicExchange()).with(Constant.HOSH_TOPIC_NEW);
    }

}

生产者

把消息发送至散列交换器 FanoutExchange

@Component
public class HoshMQSender implements RabbitTemplate.ConfirmCallback, RabbitTemplate.ReturnCallback{

    private RabbitTemplate rabbitTemplate;

    @Autowired
    public HoshMQSender(RabbitTemplate rabbitTemplate) {
        this.rabbitTemplate = rabbitTemplate;
        this.rabbitTemplate.setConfirmCallback(this);
        this.rabbitTemplate.setReturnCallback(this);
    }

    public void send(String str) {
        sendMessageWithAck(str);
    }

    private void sendMessageWithAck(String str) {
        // 消息内容
        byte[] toSendBytes = str.getBytes();
        MessageProperties messageProperties = new MessageProperties();
        messageProperties.setMessageId(String.valueOf(System.currentTimeMillis()));
        Message msg = new Message(toSendBytes, messageProperties);
        CorrelationData correlationData = new CorrelationData();
        correlationData.setId(UUID.randomUUID().toString());
//        rabbitTemplate.convertAndSend(Constant.HOSH_TOPIC_EXC, Constant.HOSH_TOPIC, msg, correlationData);
        rabbitTemplate.convertAndSend(Constant.HOSH_BROADCAST_EXC, "", msg, correlationData);

    }

    // 队列内容发送到 MQ 的确认
    @Override
    public void confirm(CorrelationData correlationData, boolean b, String s) {
//        if (b) {
//            System.out.println("recv HoshMQSender confirm id=" + correlationData.getId());
//        } else {
//            System.out.println("not recv " + s);
//        }
    }

    /**
     * exchange 到达 queue, 则 returnedMessage 不回调
     * exchange 到达 queue 失败, 则 returnedMessage 回调
     * 需要设置spring.rabbitmq.publisher-returns=true
     * @param message
     * @param replyCode
     * @param replyText
     * @param exchange
     * @param routingKey
     */
    @Override
    public void returnedMessage(Message message, int replyCode, String replyText, String exchange, String routingKey) {
        System.out.println("sender return success" + message.toString()
                +"\n replyCode "+replyCode+"\n replyText "+replyText
                +"\n exchange "+exchange + "\n routingKey "+routingKey);
    }
}

消费者

为了实现广播的效果，需要两个消费者

1、消费者1

@Component
public class HoshMqReceiver {

    @RabbitHandler
    @RabbitListener(queues = Constant.HOSH_TOPIC_NEW)
    public void onReceiver(String info, Channel channel, Message msg) throws IOException {

        System.out.println("HoshMqReceiver msg " + msg);
        System.out.println("HoshMqReceiver info " + info);
        channel.basicAck(msg.getMessageProperties().getDeliveryTag(), false);
    }
}

2、消费者2

@Component
public class HoshMqReceiver2 {

    @RabbitHandler
    @RabbitListener(queues = Constant.HOSH_TOPIC)
    public void onReceiver(String info, Channel channel, Message msg) {
        try {
            // 开启手动应答 ack 以后，只有当程序明确回复，数据已经被处理，
            // 对应数据才会被 RabbitMQ server 清除，否则保留在 RabbitMQ server 上
            channel.basicAck(msg.getMessageProperties().getDeliveryTag(), false);
            System.out.println("HoshMqReceiver2 msg " + JSON.toJSONString(msg));
            System.out.println("HoshMqReceiver2 info " + info);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

测试效果

发送消息测试一下，先看看测试结果

可以发现，在使用 FanoutExchange 后，一条消息会发送至所有与其绑定的队列中，而后，监听了对应队列的消费者就可以获取到同一条消息