RabbitMQ入门_07_Fanout 与 Topic

A. 用广播的方式实现发布订阅

参考资料:https://www.rabbitmq.com/tutorials/tutorial-three-java.html

Fanout 类型的 Exchange 以广播的方式向所有绑定到该 Exchange 的队列推送消息

下面样例代码试图使用 fanout 将状态变更消息推送给所有接入系统:

gordon.study.rabbitmq.fanout.Fanout.java

public class Fanout {
 
    private static final String EXCHANGE_NAME = "StatusUpdateFanout";
 
    public static void main(String[] argv) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = factory.newConnection();
 
        final Channel senderChannel = connection.createChannel();
        senderChannel.exchangeDeclare(EXCHANGE_NAME, "fanout");
        final CountDownLatch latch = new CountDownLatch(1);
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    for (int i = 0; i < 10;) {
                        String message = "NO. " + ++i;
                        TimeUnit.MILLISECONDS.sleep(100);
                        senderChannel.basicPublish(EXCHANGE_NAME, "", null, message.getBytes("UTF-8"));
                        System.out.printf("(%1$s)[===>%2$s    ] %3$s\n", "S", EXCHANGE_NAME + ":", message);
                        if (i == 4) {
                            latch.countDown();
                        }
                    }
                    senderChannel.close();
                } catch (Exception e) {
                }
            }
        }).start();
 
        final Channel consumerChannel1 = connection.createChannel();
        consumerChannel1.queueDeclare("SystemA", false, false, true, null);
        consumerChannel1.queueBind("SystemA", EXCHANGE_NAME, "");
        consumerChannel1.basicQos(3);
        Consumer consumer1 = new DefaultConsumer(consumerChannel1) {
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body)
                    throws IOException {
                String message = new String(body, "UTF-8");
                System.out.printf(" [    %2$s<===](%1$s) %3$s\n", "A", "SystemA", message);
                try {
                    TimeUnit.MILLISECONDS.sleep(200);
                } catch (InterruptedException e) {
                }
                consumerChannel1.basicAck(envelope.getDeliveryTag(), false);
            }
        };
        consumerChannel1.basicConsume("SystemA", false, consumer1);
 
        latch.await();
        final Channel consumerChannel2 = connection.createChannel();
        consumerChannel2.queueDeclare("SystemB", false, false, true, null);
        consumerChannel2.queueBind("SystemB", EXCHANGE_NAME, "");
        consumerChannel2.basicQos(3);
        Consumer consumer2 = new DefaultConsumer(consumerChannel2) {
            @Override
            public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body)
                    throws IOException {
                String message = new String(body, "UTF-8");
                System.out.printf(" [    %2$s<===](%1$s) %3$s\n", "B -- won't receive first 4 messages", "SystemB", message);
                try {
                    TimeUnit.MILLISECONDS.sleep(200);
                } catch (InterruptedException e) {
                }
                consumerChannel2.basicAck(envelope.getDeliveryTag(), false);
            }
        };
        consumerChannel2.basicConsume("SystemB", false, consumer2);
    }
}

代码第11行申明了名字叫 StatusUpdateFanout 的 fanout 类型 Exchange。

第33行申明了 SystemA 队列,第34行将 SystemA 队列绑定到 StatusUpdateFanout Exchange。注意到绑定路由键为空,路由键对于 fanout 类型 Exchange 无意义

同理,第20行代码发送消息时,也不用设置路由键。所有发向 fanout 类型 Exchange 的消息都会无视路由键,广播给每个绑定队列

B. 用 Topic 实现发布订阅

参考资料:https://www.rabbitmq.com/tutorials/tutorial-five-java.html

Topic 类型的 Exchange 通过支持通配符的路由键管理复杂的发布订阅关系

发送消息时指定的路由键必须是点号(.)分隔的单词,例如 sourceA.statusUpdate.systemA。

队列绑定 Exchange 时指定的路由键可以使用通配符:

  • *(星号)替代一个单词
  • #(井号)替代 0~n 个单词

对每一条消息,Exchange 会遍历所有的绑定关系,确认消息指定的路由键(例如 sourceA.statusUpdate.systemA)是否匹配绑定关系中的路由键,如果匹配,则将消息推送到相应队列(例如 sourceA.statusUpdate.systemA、*.*.systemA、*.statusUpdate.* 和 sourceA.# 都匹配,但是 sourceB.# 和 *.systemA 都不匹配)。

gordon.study.rabbitmq.topic.Topic.java

senderChannel.exchangeDeclare(EXCHANGE_NAME, "topic");

consumerChannel1.queueBind("SystemA", EXCHANGE_NAME, "#.SystemA");

consumerChannel2.queueBind("SystemB", EXCHANGE_NAME, "*.*.SystemB");

senderChannel.basicPublish(EXCHANGE_NAME, "preOrder.statusUpdate.SystemA", null, message.getBytes("UTF-8"));

C. 没有历史数据?

对于中途创建的队列(例如上面的 SystemB 队列),是没有办法获得之前的消息的。但是如果队列提前创建好,就算没有消费者,队列里依然会有全量的数据。

posted @ 2017-06-06 19:45  首夜盲毒预言家  阅读(2118)  评论(0编辑  收藏