routing

绑定是exchange和queue之间的一种关系，这可以简单的理解为：这个queue对这个exchange中的消息感兴趣。

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

绑定可以使用一个额外的routingKey参数，为了避免和basic_publish参数混淆，我们称它为binding key。我们可以这样来使用key创建一个绑定:

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

binding key的含义取决于不同的exchange类型，我们之前使用的fanout类型会直接忽略这个值。

direct类型的exchange的路由算法很简单——消息将会被传递到与它的routing key完全相同的 binding key的queue中

 1 package com.rabbitmq.www.publish_subscribe.direct;
 2 
 3 import java.util.Random;
 4 
 5 import com.rabbitmq.client.BuiltinExchangeType;
 6 import com.rabbitmq.client.ConnectionFactory;
 7 import com.rabbitmq.client.Connection;
 8 import com.rabbitmq.client.Channel;
 9 
10 public class EmitLogDirect {
11 
12   private static final String EXCHANGE_NAME = "direct_logs";
13   private final static String HOST_ADDR = "172.18.112.102";
14 
15   public static void main(String[] argv) throws Exception {
16 
17     ConnectionFactory factory = new ConnectionFactory();
18     factory.setHost(HOST_ADDR);
19     Connection connection = factory.newConnection();
20     Channel channel = connection.createChannel();
21     //申明exchange 类型direct
22     channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.DIRECT);
23 
24     for(int i=0;i<=10;i++){
25         String message = "helloworld"+i;
26         Random random = new Random();
27         String severity = "info";
28         if(random.nextInt(2)==1){
29             severity = "debug";
30         }
31         //信息发送给申明的exchange,指明routingkey 
32         channel.basicPublish(EXCHANGE_NAME, severity, null, message.getBytes("UTF-8"));
33         System.out.println(" [x] Sent '" + severity + "':'" + message + "'");
34     }
35 
36     
37 
38     channel.close();
39     connection.close();
40   }
41 
42  
43 }

package com.rabbitmq.www.publish_subscribe.direct;

import com.rabbitmq.client.*;

import java.io.IOException;

public class ReceiveLogsDirect {

  private static final String EXCHANGE_NAME = "direct_logs";
  private final static String HOST_ADDR = "172.18.112.102";

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

    channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.DIRECT);
    String queueName = channel.queueDeclare().getQueue();
    //direct类型exchange申明routekey debug
      channel.queueBind(queueName, EXCHANGE_NAME, "debug");
    
    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);
  }
}