rabbitmq(5)订阅模式

1、模型

一个生产者绑定一个交换机，每个消费者绑定一个队列。生产者将消息通过交换器分发给所有在线的消费者。
交换机没有消息存储的能力，只能向当前在线的消费者发送消息。因此未接收到消息的消费者，即使重新连接rabbitmq也无法获取到已发送的消息

订阅模式与普通队列的区别：
1. 普通队列中生产者发送的消息只能有一个消费者接受到；订阅模式中生产者发送的消息会被所有在线的消费者接收到；
2. 普通队列中生产者消息会被储存，即使消费者没有成功接受到消息，重新上线后也可以重新收到该消息；订阅模式中生产者消息不会被储存；

2、代码

2.1、生产者

private final static String EXCHANGE_NAME = "test_exchange";

@Test
public void testSend() throws Exception {
    ConnectionFactory factory = new ConnectionFactory();
    factory.setHost("192.168.1.7");
    factory.setUsername("root");
    factory.setPassword("123456");

    Connection connection = factory.newConnection();
    Channel channel = connection.createChannel();

    /* 
     * 申明交换机, fanout:分发
     * 交换机没有消息存储的能力,只能向当前在线的消费者发送消息
     * 未接收到消息的消费者,即使重新连接rabbitmq也无法获取到已发送的消息
     */
    channel.exchangeDeclare(EXCHANGE_NAME, "fanout");

    String message = "Hello world";
    channel.basicPublish(EXCHANGE_NAME, "", null, message.getBytes());
    System.out.println(" [1] Sent '" + message + "'");

    channel.close();
    connection.close();
}

2.2、消费者1

private final static String EXCHANGE_NAME = "test_exchange";

public static void main(String[] args) throws Exception {
    ConnectionFactory factory = new ConnectionFactory();
    factory.setHost("192.168.1.7");
    factory.setUsername("root");
    factory.setPassword("123456");

    Connection connection = factory.newConnection();
    final Channel channel = connection.createChannel();

    channel.exchangeDeclare(EXCHANGE_NAME, "fanout");
    String queueName = channel.queueDeclare().getQueue();
    // 绑定队列到交换机转发器
    channel.queueBind(queueName, EXCHANGE_NAME, "");

    System.out.println(" [1] Waiting for messages. To exit press CTRL+C");
    Consumer consumer = new DefaultConsumer(channel) {
        @Override
        public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
                byte[] body) throws IOException {
            String message = new String(body, "UTF-8");
            System.out.println(" [1] Received '" + message + "'");

            channel.basicAck(envelope.getDeliveryTag(), false);
        }
    };
    boolean autoAck = false;
    channel.basicConsume(queueName, autoAck, consumer);
}

2.2、消费者2

private final static String EXCHANGE_NAME = "test_exchange";

public static void main(String[] args) throws Exception {
    ConnectionFactory factory = new ConnectionFactory();
    factory.setHost("192.168.1.7");
    factory.setUsername("root");
    factory.setPassword("123456");

    Connection connection = factory.newConnection();
    final Channel channel = connection.createChannel();

    channel.exchangeDeclare(EXCHANGE_NAME, "fanout");
    String queueName = channel.queueDeclare().getQueue();
    // 绑定队列到交换机转发器
    channel.queueBind(queueName, EXCHANGE_NAME, "");

    System.out.println(" [2] Waiting for messages. To exit press CTRL+C");
    Consumer consumer = new DefaultConsumer(channel) {
        @Override
        public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
                byte[] body) throws IOException {
            String message = new String(body, "UTF-8");
            System.out.println(" [2] Received '" + message + "'");

            channel.basicAck(envelope.getDeliveryTag(), false);
        }
    };
    boolean autoAck = false;
    channel.basicConsume(queueName, autoAck, consumer);
}