任何发送到Topic Exchange的消息都会被转发到所有关联RouteKey中指定“topic”的队列上上

  1. 这种模式下需要RouteKey，客户端要提前绑定Exchange与Queue。
  2. 如果Exchange没有发现能够与RouteKey匹配的Queue，则会抛弃此消息。
  3. 客户端在进行绑定时，要提供一个该队列“感兴趣”的主题，如“#.log.#”表示该队列关心所有涉及log的消息(一个RouteKey为”MQ.log.error”的消息会被转发到该队列)。
  4. “#”表示0个或若干个关键字，“”表示一个关键字。如“log.”能与“log.warn”匹配，无法与“log.warn.timeout”匹配；但是“log.#”能与上述两者匹配。

RabbitMQ的Exchange 模式之topic（主题模式）_客户端
简单解释一下上图，一个消息产生者P，一个模式为topic的Exchange（交换机），两个队列，两个消息消费者。

在topic模式下：

如果一个消息的 routing key设置 ​​​"quick.orange.rabbit"​​​

即如下

channel.basicPublish(EXCHANGE_NAME, "quick.orange.rabbit", null, "hello".getBytes());

那么该消息将被转发（推送）至Q1、Q2两个队列

如果一个消息的 routing key设置 ​​​"quick.orange.fox"​​​

那么该消息将只会被转发（推送）至Q1队列

如果一个消息的 routing key设置 ​​​"quick.orange.fox"​​​

那么该消息将只会被转发（推送）至Q2队列

当然，如果一个消息的 routing key设置 ​​​" quick.brown.fox "​​​

那么该消息将不会被转发（推送）到任何队列，它将会丢失，即丢弃该消息

前面提到客户端要提前绑定Exchange与Queue

channel.exchangeDeclare(EXCHANGE_NAME, "topic");

并且需要获取一个新的空队列，用来与EXCHANGE进行binding

String queueName = channel.queueDeclare().getQueue();

然后设置你关心的主题

channel.queueBind(queueName, EXCHANGE_NAME, "*.orange.*");

如此这般，这个客户端就只会获取到自己“感兴趣”的主题对应的消息

栗子：
服务端推送主题如下的消息，即routingKey分别为如下值

"adtec.laoliu","ali.xiaowang", "tencent.laozhang", "adtec.xiaohu"
package com.adtec.rabbitmq;


import com.rabbitmq.client.*;

public class EmitLogTopic {

    private static final String EXCHANGE_NAME = "topic";
    private static final String[] routingKeys = { "adtec.laoliu","ali.xiaowang", "tencent.laozhang", "adtec.xiaohu" };

    public static void main(String[] argv) throws Exception {

        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        Connection connection = factory.newConnection();

        Channel channel = connection.createChannel();

        channel.exchangeDeclare(EXCHANGE_NAME, "topic");

        String message = getMessage("hello");

        //分别推送"adtec.laoliu","ali.xiaowang", "tencent.laozhang", "adtec.xiaohu"消息
        for (String routingKey : routingKeys) {
            String msg = message+ "' from "+routingKey;
            channel.basicPublish(EXCHANGE_NAME, routingKey, null, msg.getBytes());
            System.out.println(" [x] Sent '" + routingKey + "':'" + message + "'");
        }
        channel.close();
        connection.close();

    }

    private static String getMessage(String strings) {

        return "info: Hello World!";
    }
}

客户端只对adtec相关的主题感兴趣，即routingKey值为​​#.adtec.#​​

package rabbitmq;

import com.rabbitmq.client.*;

import java.io.IOException;

public class ReceiveLogsTopic {
  private static final String EXCHANGE_NAME = "topic";
  private static final String[] bindingKeys = { "adtec.laoliu", "adtec.xiaowang","adtec.xiaozhou","adtec.xiaohu" };
  public static void main(String[] argv) throws Exception {
    ConnectionFactory factory = new ConnectionFactory();
    factory.setHost("localhost");
    Connection connection = factory.newConnection();
    Channel channel = connection.createChannel();

    channel.exchangeDeclare(EXCHANGE_NAME, "topic");
    String queueName = channel.queueDeclare().getQueue();

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

    //binding那些bindingKey
    //可以单个单个设置，也可以批量设置
    for (String bindingKey : bindingKeys) {
      channel.queueBind(queueName, EXCHANGE_NAME, "#.adtec.#");
    }

    System.out.println(" [*] 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(" [x] Received '" + envelope.getRoutingKey() + "':'" + message + "'");
      }
    };
    channel.basicConsume(queueName, true, consumer);
  }
}

测试，先运行客户端，再运行服务端

服务端发布的消息

RabbitMQ的Exchange 模式之topic（主题模式）_客户端_02

客户端订阅的消息

RabbitMQ的Exchange 模式之topic（主题模式）_服务端_03