RabbitMq之Publish/Subscribe

在之前的例子中,rabbit传递消息的形式如下:

1.send发送消息到指定的一个队列中

2.队列充当一个消息存储容器.

3.consumer从队列中消费消息.

当存在多个consumer消费者的时候,rabbitmq会比较平均的分配消息给每个consumer,也就是说,每个consumer获取的消息都是队列消息的一个子集.

而在发布/订阅这种模式中,消息传递模型的核心思想是，生产者不发送任何信息直接到队列。事实上，生产者也不知道消息是否会被传送到任何队列。 rabbitmq引入了一个中间者exchanges. 

Exchanges

1.send发送消息到指定的一个exchanges中

2.可以将任意的队列绑定到exchanges中,并且消息会随着exchanges的广播发送到队列中

3.队列充当一个消息存储容器.

4.consumer从队列中消费消息.

生产者只能发送消息到Exchange。exchanges是件很简单的事。一方面它接收来自生产者和另一方的消息，并将它们推送到队列中。Exchange必须知道它接收哪些消息。是否应该附加到特定队列？它应该被附加到多个队列吗？或者它应该被丢弃。该规则由Exchange类型定义。 

exchanges有几种类型:direct, topic, headers and fanout

更多请查看:http://blog.csdn.net/yzr_java/article/details/70916084

Listing exchanges

可以在命令行中监听exchanges:    rabbitmqctl list_exchanges

Temporary queues

临时队列:由rabbitmq服务器自动创建的队列,当连接关闭时,临时队列将会被自动删除.

exchanges可以配合使用临时队列,将消息广播到临时队列中.

//服务器创建队列
String queueName = channel.queueDeclare().getQueue();

Bindings

将队列绑定到exchanges中,当exchanges进行广播的时候,被绑定的队列将会接收到消息.

//将队列绑定到exchange
channel.queueBind(queueName, EXCHANGE_NAME, "");

Listing bindings

可以使用命令行监听: rabbitmqctl list_bindings

package yzr.main;

import java.io.IOException;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Consumer;
import com.rabbitmq.client.DefaultConsumer;
import com.rabbitmq.client.Envelope;

public class ReceiveLogs {

	private static final String EXCHANGE_NAME = "logs";

	  public static void main(String[] argv) throws Exception {
	    ConnectionFactory factory = new ConnectionFactory();
	    factory.setHost("localhost");
	    Connection connection = factory.newConnection();
	    Channel channel = connection.createChannel();
	    //创建exchange
            //fanout将消息广播到队列中
	    channel.exchangeDeclare(EXCHANGE_NAME, "fanout");
	    //服务器创建队列
	    String queueName = channel.queueDeclare().getQueue();
	    //将队列绑定到exchange
	    channel.queueBind(queueName, EXCHANGE_NAME, "");

	    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 '" + message + "'");
	      }
	    };
	    channel.basicConsume(queueName, true, consumer);
	  }

}

测试:

启动上面的ReceiveLogs类,然后http://localhost:15672登陆之后看一下exchanges视图:

然后再看一下队列视图:

发送消息:

 [x] Sent '111 message.'
 [x] Sent '211 message..'
 [x] Sent '311 message...'
 [x] Sent '411 message....'
 [x] Sent '511 message.....'
 [x] Sent '611 message.....'
 [x] Sent '711 message.....'
 [x] Sent '811 message.....'
 [x] Sent '911 message.....'