RabbitMQ的基礎使用 —— Topic模式

原創

2020-07-03 04:33

我們在AMQP及RabbitMQ概論中，介紹交換器類型的時候，就曾提到過Topic模式，該模式其實和ActiveMQ通配符式訂閱非常的類似，所以這裏我們就不過於詳細介紹了，直接來簡單看一下小例子吧。

和RabbitMQ中的Direct、Fanout模式類似，在使用時，我們只需將交換器的類型修改爲Topic即可，然後我們通過生產者來發布消息，這裏我們就一共發佈了9條測試消息，如下：

public class TopicProducer {

    //交換器名稱
    public static final String EXCHANGE_NAME = "logs";

    public static void main(String[] args) throws Exception {
        //創建連接,連接到RabbitMQ
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("127.0.0.1");
        Connection connection = connectionFactory.newConnection();

        //創建信道
        Channel channel = connection.createChannel();
        //創建交換器
        channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.TOPIC);

        //定義的業務日誌消息級別，即作爲路由鍵使用
        String[] logLevels = {"error.controller.A", "warn.controller.A", "info.controller.A",
                              "error.service.B", "warn.service.B", "info.service.B",
                              "error.mapper.C", "warn.controller.C", "info.controller.C"};
        for (int i = 0; i < logLevels.length; i++) {
            String logLevel = logLevels[i];
            String msg = "Hello RabbitMQ";

            //發佈消息，需要參數：交換器、路由鍵，其中以日誌消息級別爲路由鍵
            channel.basicPublish(EXCHANGE_NAME, logLevel, null, msg.getBytes(Charset.forName("UTF-8")));
        }
        channel.close();
        connection.close();
    }
}

然後我們來看一看消費者是如何通過#、*來獲取指定的消息的，這裏我們先來獲取所有的消息，如下：

public class TopicConsumer {

    public static final String EXCHANGE_NAME = "logs";

    public static void main(String[] args) throws Exception {
        //創建連接,連接到RabbitMQ,與發送端一樣
        ConnectionFactory connectionFactory = new ConnectionFactory();
        connectionFactory.setHost("127.0.0.1");
        Connection connection = connectionFactory.newConnection();

        //創建信道
        Channel channel = connection.createChannel();
        //可不創建，由生產者進行創建
        channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.TOPIC);

        String queueName = channel.queueDeclare().getQueue();  //聲明一個隨機隊列

        channel.queueBind(queueName, EXCHANGE_NAME, "#");

        //聲明瞭一個消費者
        Consumer consumer = new DefaultConsumer(channel){
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
                String message = "Exchange: " + envelope.getExchange() + ", " +
                                "RoutingKey: " + envelope.getRoutingKey() + ", " +
                                "Content: " + new String(body, "UTF-8");
                System.out.println(message);
            }
        };
        //消費者正式開始在指定隊列上消費消息
        channel.basicConsume(queueName, true, consumer);
    }
}