RabbitMQ示例代码（三）

3.一个生产者（发布方）多个消费者（订阅方）模式

发布订阅模型，使用自定义exchange，类型为fanout，不绑定特定queue，一个发送者，多个接收者。
Exchange的类型有：direct, fanout, topic, headers

发送方-->(自定义Exchange,fanout)-->Queue1-->接收方1
                                 |
                                  -->Queue2-->接收方2
                              
（1）生产者
import com.rabbitmq.client.BuiltinExchangeType;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;

public class EmitLog {

    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();
        // 自定义Exchange，类型为fanout
        channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.FANOUT);
        String message = getMessage(argv);
        channel.basicPublish(EXCHANGE_NAME, "", null, message.getBytes("UTF-8"));
        System.out.println(" [x] Sent '" + message + "'");
        channel.close();
        connection.close();
    }

    private static String getMessage(String[] strings) {
        if (strings.length < 1) {
            return "info: Hello World Publish/Subscribe!";
        }
        return joinStrings(strings, " ");
    }

    private static String joinStrings(String[] strings, String delimiter) {
        int length = strings.length;
        if (length == 0) {
            return "";
        }
        StringBuilder words = new StringBuilder(strings[0]);
        for (int i = 1; i < length; i++) {
            words.append(delimiter).append(strings[i]);
        }
        return words.toString();
    }
}

（2）消费者
import com.rabbitmq.client.*;

import java.io.IOException;

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();
        channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.FANOUT);
        // 获取随机命名的queue名称
        String queueName = channel.queueDeclare().getQueue();
        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);
    }
    
}