易学笔记-RabbitMQ教程4：选择性接收消息（路由器类型为：direct）

• RabbitMQ教程4：选择性接收消息

1. 代码基础： 易学笔记-RabbitMQ教程3：一个消息发给所有消费者（路由器类型为：fanout）
2. 交换器（路由器）：
   1. Exchange 选择 “direct”，而不是“fanout”
   2.  channel.basicPublish(EXCHANGE_NAME,severity，第二个参数 severity 为关键字
3. 临时队列
   1. channel.queueBind(queueName, EXCHANGE_NAME, severity); 第二个参数 severity 为关键字，该关键字和交换器的关键字一致时才会被加入队列
   2. 一个队列可以绑定一个交换器的多个关键字
5. 新建生产者：

   package oneProductAllConsume;
   
   import com.rabbitmq.client.BuiltinExchangeType;
   import com.rabbitmq.client.ConnectionFactory;
   import com.rabbitmq.client.Connection;
   import com.rabbitmq.client.Channel;
   
   public class EmitLogDirect {
   
       private static final String EXCHANGE_NAME = "direct_logs";
   
       public static void main(String[] argv) throws Exception {
           //创建连接
           ConnectionFactory factory = new ConnectionFactory();
           factory.setHost("192.168.65.129");
           Connection connection = factory.newConnection();
           Channel channel = connection.createChannel();
           //声明路由器和路由器的类型
           channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.DIRECT);
           
           String severity = "warning";
           String message = ".........i am msg.........";
   
           //发布消息
           channel.basicPublish(EXCHANGE_NAME, severity, null, message.getBytes("UTF-8"));
           System.out.println(" [x] Sent '" + severity + "':'" + message + "'");
   
           channel.close();
           connection.close();
       }
       
   }
   

   1. 发布消息绑定关键字

       String message = ".........i am msg.........";

              String severity = "warning";

              //发布消息

              channel.basicPublish(EXCHANGE_NAME, severity, null, message.getBytes("UTF-8"));

6. 新建消费者：

   package oneProductAllConsume;
   
   import com.rabbitmq.client.*;
   import java.io.IOException;
   
   public class ReceiveLogsDirect {
   
       private static final String EXCHANGE_NAME = "direct_logs";
   
       public static void main(String[] argv) throws Exception {
           //建立连接和通道
           ConnectionFactory factory = new ConnectionFactory();
           factory.setHost("192.168.65.129");
           Connection connection = factory.newConnection();
           Channel channel = connection.createChannel();
           //声明路由器和类型
           channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.DIRECT);
           //声明队列
           String queueName = channel.queueDeclare().getQueue();
           //定义要监听的级别
           String[] severities = {"info", "warning", "error"};
           //根据绑定键绑定
           for (String severity : severities) {
               channel.queueBind(queueName, EXCHANGE_NAME, severity);
           }
           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);
       }
   }
   

   1. 队列、交换器和关键字绑定

       //定义要监听的级别

              String[] severities = {"info", "warning", "error"};

              //根据绑定键绑定

              for (String severity : severities) {

                  channel.queueBind(queueName, EXCHANGE_NAME, severity);

              }

7. 测试
   1. 发布者发布 info类型消息

       [x] Sent 'info':'.........i am msg.........'

   2. 接受者接收info类型消息

       [*] Waiting for messages. To exit press CTRL+C

       [x] Received 'info':'.........i am msg.........'

   3. 发布者发布warn类型消息

       [x] Sent 'warn':'.........i am msg.........'

   4. 接受者由于只接收这三种消息：info、warning、error，不包含：warn，所以没有接收