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在RabbitMQ中,producer只能将消息发送到一个exchange中。要理解exchange也非常简单,它一边负责接收producer发送的消息, 另一边将消息推送到queue中。exchange必须清楚的知道在收到消息之后该如何进行下一步的处理,比如是否应该将这条消息发送到某个queue中? 还是应该发送到多个queue中?还是应该直接丢弃这条消息等等。
RabbitMQ中的exchange类型有这么几种:direct,topic,headers以及fanout。这一小节将会主要介绍最后一种类型——fanout。 使用RabbitMQ的client来创建一个fanout类型的exchange。fanout类型的exchange非常简单,从名字也可以猜测出来,它会向所有的queue广播所有收到的消息。这正是我们的log系统需要的。
package com.rabbitmq.www.publish_subscribe;
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";
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();
//定义exchange
channel.exchangeDeclare(EXCHANGE_NAME, BuiltinExchangeType.FANOUT);
for(int i=0;i<=10;i++){
String message = "helloworld"+i;
//信息发送给申明的exchange
channel.basicPublish(EXCHANGE_NAME, "", null, message.getBytes("UTF-8"));
System.out.println(" [x] Sent '" + message );
}
channel.close();
connection.close();
}
}
package com.rabbitmq.www.publish_subscribe;
import com.rabbitmq.client.*;
import java.io.IOException;
public class ReceiveLogs {
private static final String EXCHANGE_NAME = "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.FANOUT);
//服务器为创建随机queue提供了一个无参数的queueDeclare()方来来创建一个非持久化的、独有的并且是自动删除的已命名的queue。
String queueName = channel.queueDeclare().getQueue();
//现在我们需要告诉exchange将消息发送到我们的queue中。 这种exchange和queue的关系称为绑定(binding)。
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);
}
} |
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