RabbitMQ学习总结第五篇：路由Routing

Q1对所有橘色的（orange）的动物感兴趣；
Q2希望能拿到所有兔子的（rabbit）信息，还有比较懒惰的（lazy.#）动物信息。

一条以” quick.orange.rabbit”为routing key的消息将会推送到Q1和Q2两个queue上，routing key为“lazy.orange.elephant”的消息同样会被推送到Q1和Q2上。但如果routing key为”quick.orange.fox”的话，消息只会被推送到Q1上；routing key为”lazy.brown.fox”的消息会被推送到Q2上，routing key为"lazy.pink.rabbit”的消息也会被推送到Q2上，但同一条消息只会被推送到Q2上一次。

如果在发送消息时所指定的exchange和routing key在消费者端没有对应的exchange和binding key与之绑定的话，那么这条消息将会被丢弃掉。例如："orange"和"quick.orange.male.rabbit"。但是routing为”lazy.orange.male.rabbit”的消息，将会被推到Q2上。

Topic类型的exchange：

Topic类型的exchange是很强大的，也可以实现其它类型的exchange。

当一个队列被绑定为binding key为”#”时，它将会接收所有的消息，此时和fanout类型的exchange很像。
当binding key不包含”*”和”#”时，这时候就很像direct类型的exchange。

2、最终实现

我们准备在日志系统中使用topic类型的exchange。开始我们准备routing keys使用两个单词："<facility>.<severity>"。代码和上篇博文里的差不多，EmitLogTopic.java:

public class EmitLogTopic {
    private static final String EXCHANGE_NAME = "topic_logs";

    public static void main(String[] argv)
                  throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        //指定一个topic类型的exchange
        channel.exchangeDeclare(EXCHANGE_NAME, "topic");

        //这里拿到routing key
        String routingKey = getRouting(argv);
        String message = getMessage(argv);
        channel.basicPublish(EXCHANGE_NAME, routingKey, null, message.getBytes());
        System.out.println(" [x] Sent '" + routingKey + "':'" + message + "'");

        connection.close();
    }
    //...
}

ReceiveLogsTopic.java的代码：

public class ReceiveLogsTopic {
    private static final String EXCHANGE_NAME = "topic_logs";
    public static void main(String[] argv)
                  throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = factory.newConnection();
        Channel channel = connection.createChannel();

        //指定一个topic类型的exchange
        channel.exchangeDeclare(EXCHANGE_NAME, "topic");
        String queueName = channel.queueDeclare().getQueue();

        if (argv.length < 1){
            System.err.println("Usage: ReceiveLogsTopic [binding_key]...");
            System.exit(1);
        }

        //绑定binding key
        for(String bindingKey : argv){
            channel.queueBind(queueName, EXCHANGE_NAME, bindingKey);
        }

        System.out.println(" [*] Waiting for messages. To exit press CTRL+C");
        QueueingConsumer consumer = new QueueingConsumer(channel);
        channel.basicConsume(queueName, true, consumer);

        while (true) {
            QueueingConsumer.Delivery delivery = consumer.nextDelivery();
            String message = new String(delivery.getBody());
            String routingKey = delivery.getEnvelope().getRoutingKey();

            System.out.println(" [x] Received '" + routingKey + "':'" + message + "'");
        }
    }
}

运行情况如下：

RabbitMQ学习总结第五篇：路由Routing

3、总结

在上边的基础上，只是丰富了routing key和binding key的写法。

参考链接：http://www.rabbitmq.com/tutorials/tutorial-five-java.html