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RabbitMQ - exchange

2024-08-03 23:05:04   225人阅读

总结一下几种ExchangeTypes。


之前写发布/订阅模式时第一次提到了exchange type。
即producer不是将消息直接放到队列中，而是先到exchange中，exchange主要用于控制消息到队列的路由,根据具体的exchange type将消息传给需要的队列或者直接废弃。
在这一篇中总结一下那些用到的exchange type。


一.Direct Exchange
direct exchange算是最基本的了。
direct exchange用于将带上routing key的消息传值拥有相同routing key的队列中。


当我们想用一个简单的标识符区别所有传入同一个exchange中的消息时direct exchange就非常合适。

private static String DIRECT_EXCHANGE = "DIRECT_EXCHAGNE";     static class FanoutProducer {        public static void main(String[] args) throws IOException {            ConnectionFactory connectionFactory = new ConnectionFactory();            Connection connection = connectionFactory.newConnection();            Channel channel= connection.createChannel();;             String content = "I miss the conversation";            channel.exchangeDeclare(DIRECT_EXCHANGE, ExchangeTypes.DIRECT);            channel.basicPublish(DIRECT_EXCHANGE, "alvez", null, content.getBytes());        }    }     static class FanoutConsumer {        public static void main(String[] args) throws IOException, InterruptedException {            ConnectionFactory connectionFactory = new ConnectionFactory();            Connection connection = connectionFactory.newConnection();            Channel channel= connection.createChannel();             String queueName = channel.queueDeclare().getQueue();            channel.queueBind(queueName, DIRECT_EXCHANGE, "alvez");             QueueingConsumer consumer = new QueueingConsumer(channel);            String s = channel.basicConsume(queueName, true, consumer);            System.out.println(s);            while (true) {                QueueingConsumer.Delivery delivery = consumer.nextDelivery();                String message = new String(delivery.getBody());                String routingKey = delivery.getEnvelope().getRoutingKey();                 System.out.println("From:" + routingKey + "‘:‘" + message + "‘");            }         }
}

 

 

二.Fanout Exchange
fanout和routing key无关，它将消息无差别地(indiscriminately)传送给所有队列。

fanout exchange通常用于发布/订阅模式。
将消息传送给不同的队列，不同的队列对同一种消息采取不同的行为。
比如，现在有一个客户订单消息被三个队列接收，队列1完成该订单，队列2将订单写入日志，队列3将订单发给别的部门什么的。
比如下面的代码，消费者可以获得routing key并输出，但能否获取与routing key无关：

    private static String FANOUT_EXCHANGE = "FANOUT_EXCHANGE";     static class DirectProducer {        public static void main(String[] args) throws IOException {            ConnectionFactory connectionFactory = new ConnectionFactory();            Connection connection = connectionFactory.newConnection();            Channel channel= connection.createChannel();;             String content = "I miss the conversation";            channel.exchangeDeclare(FANOUT_EXCHANGE, ExchangeTypes.FANOUT);            channel.basicPublish(FANOUT_EXCHANGE, "alvez", null, content.getBytes());        }    }     static class DirectConsumer {        public static void main(String[] args) throws IOException, InterruptedException {            ConnectionFactory connectionFactory = new ConnectionFactory();            Connection connection = connectionFactory.newConnection();            Channel channel= connection.createChannel();             String queueName = channel.queueDeclare().getQueue();            channel.queueBind(queueName, FANOUT_EXCHANGE, "");             QueueingConsumer consumer = new QueueingConsumer(channel);            String s = channel.basicConsume(queueName, true, consumer);            System.out.println(s);            while (true) {                QueueingConsumer.Delivery delivery = consumer.nextDelivery();                String message = new String(delivery.getBody());                String routingKey = delivery.getEnvelope().getRoutingKey();                 System.out.println("From:" + routingKey + "‘:‘" + message + "‘");            }         }     }

 

 

三.Topic Exchange
如果根据topic exchange用法说明其特征的话反而更麻烦。
topic exchange正如其名，就是根据某种主题而不是特定的标题，也就是可以匹配routing key的一部分或者全部。
topic exchange的routing key可以有多个词组成，词用‘.‘分隔。
routing key中可以包括‘*‘或者‘#‘，‘*‘表示一个词，‘#‘表示0～N个词。

比如消息发布时routing key为"honda.civic.navy"，
能接收消息的队列的routing key可以是"honda.civic.navy"或"*.civic.*"或"honda.#"或"#"，
但不能是"honda.accord.navy"或"honda.accord.silver"或"*.accord.*"或"ford.#"。

    private static String TOPIC_EXCHANGE = "TOPIC_EXCHAGNE";     static class TopicProducer {        public static void main(String[] args) throws IOException {            ConnectionFactory connectionFactory = new ConnectionFactory();            Connection connection = connectionFactory.newConnection();            Channel channel= connection.createChannel();;             String content = "I miss the conversation";            channel.exchangeDeclare(TOPIC_EXCHANGE, ExchangeTypes.TOPIC);            channel.basicPublish(TOPIC_EXCHANGE, "alvez.dep.FBI.map", null, content.getBytes());        }    }     static class TopicConsumer {        public static void main(String[] args) throws IOException, InterruptedException {            ConnectionFactory connectionFactory = new ConnectionFactory();            Connection connection = connectionFactory.newConnection();            Channel channel= connection.createChannel();             String queueName = channel.queueDeclare().getQueue();            channel.queueBind(queueName, TOPIC_EXCHANGE, "alvez.#");             QueueingConsumer consumer = new QueueingConsumer(channel);            String s = channel.basicConsume(queueName, true, consumer);            System.out.println(s);            while (true) {                QueueingConsumer.Delivery delivery = consumer.nextDelivery();                String message = new String(delivery.getBody());                String routingKey = delivery.getEnvelope().getRoutingKey();                 System.out.println("From:" + routingKey + "‘:‘" + message + "‘");            }         }}

 

 

四.Headers Exchange
即消息头和队列中声明的消息头匹配时可以通信。
就可以定义多个条件进行匹配这一点来说，headers exchange和topic exchange有些相似。
有时候会给人"为什么会有这种东西?"的感觉，相比topic exchage有什么优势?
如果仅仅说"headers exchange是基于headers的，topic exchange是基于routing key的"，这种回答没什么意义。

代码如下，可以看到producer和consumer的routing key是不同的，producer的header通过properties对象传输：

private static String HEADERS_EXCHANGE = "HEADERS_EXCHANGE";     static class HeadersProducer {        public static void main(String[] args) throws IOException {            ConnectionFactory connectionFactory = new ConnectionFactory();            Connection connection = connectionFactory.newConnection();            Channel channel = connection.createChannel();             String content = "I miss the conversation";            channel.exchangeDeclare(HEADERS_EXCHANGE, ExchangeTypes.HEADERS);            AMQP.BasicProperties properties = new AMQP.BasicProperties();            Map<String,Object> map = new HashMap<>();            map.put("key1","val1");            properties.setHeaders(map);             channel.basicPublish(HEADERS_EXCHANGE, "alvez", properties, content.getBytes());         }    }     static class HeadersConsumer {        public static void main(String[] args) throws IOException, InterruptedException {            ConnectionFactory connectionFactory = new ConnectionFactory();            Connection connection = connectionFactory.newConnection();            Channel channel = connection.createChannel();             String queueName = channel.queueDeclare().getQueue();            Map<String, Object> headers = new HashMap<>();            headers.put("key1","val1");            headers.put("key2","val2");            headers.put("key3","val3");            headers.put("key4","val4");            channel.queueBind(queueName, HEADERS_EXCHANGE, "",headers);             QueueingConsumer consumer = new QueueingConsumer(channel);            String s = channel.basicConsume(queueName, true, consumer);            System.out.println(s);            while (true) {                QueueingConsumer.Delivery delivery = consumer.nextDelivery();                String message = new String(delivery.getBody());                String routingKey = delivery.getEnvelope().getRoutingKey();                 System.out.println("From:" + routingKey + "‘:‘" + message + "‘");            }         }     }

 

(ps:图不错，感谢图片作者。)

RabbitMQ - exchange


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