消息中间件踩坑之旅——RabbitMq简介加交换器类型（一）

简介

1. RabbitMq是一个消息中间件，应用可以通过消息中间件来进行通信。
2. RabbitMq整体上是一个生产者消费者的模式，主要负责接收、储存、转发消息
3. AMQP协议 ???? 发送：Basic.Publish 接收：Basic.Consume
4. 其中消息只能储存在队列中
5. 默认在多个消费者情况下，采用轮询处理，也就是平均分摊

名称	解释
producer	生产者，消息投递的一方，包含消息体(payload)与(label)、消息体一般是一个带有业务逻辑结构的数据，比如json字符串也可以对消息体进行序列化；消息标签是用来表述这条消息、比如交换器的名称或者路由键
exchange	交换器，类型：常用类型有：fanout、direct、topic、headers
consumer	消费者、取出数据实现具体业务
RoutingKey	路由键、用来指定这个消息的路由规则；需要与交换器绑定键联合起来才能生效
Binding	绑定、通过绑定将交换器和队列关联到一起；绑定时同时指出一个绑定键
queue

交换器类型

The default exchange is a direct exchange with no name (empty string) pre-declared by the broker. It has one special property that makes it very useful for simple applications: every queue that is created is automatically bound to it with a routing key which is the same as the queue name.

fanout

他把所有发送到该交换器的消息路由到所有与该交换器绑定的队列中

channel.exchangeDeclare("logs", "fanout");

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");
    try (Connection connection = factory.newConnection();
         Channel channel = connection.createChannel()) {
        channel.exchangeDeclare(EXCHANGE_NAME, "fanout");

        //String.join() 是用一个参数连接后面那个字符串数组
        String message = argv.length < 1 ? "info: Hello World!" :
                            String.join(" ", argv);

        channel.basicPublish(EXCHANGE_NAME, "", null, message.getBytes("UTF-8"));
        System.out.println(" [x] Sent '" + message + "'");
    }
  }
}

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, "fanout");
    String queueName = channel.queueDeclare().getQueue();
    channel.queueBind(queueName, EXCHANGE_NAME, "");

    System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

    DeliverCallback deliverCallback = (consumerTag, delivery) -> {
        String message = new String(delivery.getBody(), "UTF-8");
        System.out.println(" [x] Received '" + message + "'");
    };
    channel.basicConsume(queueName, true, deliverCallback, consumerTag -> { });
  }
}

direct

他会把消息与那些BindingKey和RoutingKey

channel.exchange_declare(exchange='direct_logs',
                         exchange_type='direct')

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

public class EmitLogDirect {

  private static final String EXCHANGE_NAME = "direct_logs";

  public static void main(String[] argv) throws Exception {
    ConnectionFactory factory = new ConnectionFactory();
    factory.setHost("localhost");
    try (Connection connection = factory.newConnection();
         Channel channel = connection.createChannel()) {
        channel.exchangeDeclare(EXCHANGE_NAME, "direct");

        String severity = getSeverity(argv);
        String message = getMessage(argv);

        channel.basicPublish(EXCHANGE_NAME, severity, null, message.getBytes("UTF-8"));
        System.out.println(" [x] Sent '" + severity + "':'" + message + "'");
    }
  }
  //..
}

import com.rabbitmq.client.*;

public class ReceiveLogsDirect {

  private static final String EXCHANGE_NAME = "direct_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, "direct");
    String queueName = channel.queueDeclare().getQueue();

    if (argv.length < 1) {
        System.err.println("Usage: ReceiveLogsDirect [info] [warning] [error]");
        System.exit(1);
    }

      //绑定
    for (String severity : argv) {
        channel.queueBind(queueName, EXCHANGE_NAME, severity);
    }
    System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

    DeliverCallback deliverCallback = (consumerTag, delivery) -> {
        String message = new String(delivery.getBody(), "UTF-8");
        System.out.println(" [x] Received '" +
            delivery.getEnvelope().getRoutingKey() + "':'" + message + "'");
    };
    channel.basicConsume(queueName, true, deliverCallback, consumerTag -> { });
  }
}

topic

direct是严格比配、但是这种严格匹配方式在很多情况下不能满足实际的业务需求

The binding key must also be in the same form. The logic behind the topic exchange is similar to a direct one - a message sent with a particular routing key will be delivered to all the queues that are bound with a matching binding key. However there are two important special cases for binding keys:

• * (star) can substitute for exactly one word. 匹配一个单词
• # (hash) can substitute for zero or more words 匹配多个单词或者0个

​ Topic exchange

Topic exchange is powerful and can behave like other exchanges.

When a queue is bound with “#” (hash) binding key - it will receive all the messages, regardless of the routing key - like in fanout exchange.

When special characters “*” (star) and “#” (hash) aren’t used in bindings, the topic exchange will behave just like a direct one.

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;

public class EmitLogTopic {

  private static final String EXCHANGE_NAME = "topic_logs";

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

        channel.exchangeDeclare(EXCHANGE_NAME, "topic");

        String routingKey = getRouting(argv);
        String message = getMessage(argv);

        channel.basicPublish(EXCHANGE_NAME, routingKey, null, message.getBytes("UTF-8"));
        System.out.println(" [x] Sent '" + routingKey + "':'" + message + "'");
    }
  }
  //..
}

import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.DeliverCallback;

public class ReceiveLogsTopic {

  private static final String EXCHANGE_NAME = "topic_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, "topic");
    String queueName = channel.queueDeclare().getQueue();

    if (argv.length < 1) {
        System.err.println("Usage: ReceiveLogsTopic [binding_key]...");
        System.exit(1);
    }

    for (String bindingKey : argv) {
        channel.queueBind(queueName, EXCHANGE_NAME, bindingKey);
    }

    System.out.println(" [*] Waiting for messages. To exit press CTRL+C");

    DeliverCallback deliverCallback = (consumerTag, delivery) -> {
        String message = new String(delivery.getBody(), "UTF-8");
        System.out.println(" [x] Received '" +
            delivery.getEnvelope().getRoutingKey() + "':'" + message + "'");
    };
    channel.basicConsume(queueName, true, deliverCallback, consumerTag -> { });
  }
}

header

header类型是交换器不依赖于路由键的匹配规则、而是根据发送的信息内容中的headers属性进行匹配（也是个键值对）

交换器类型还有很多 ，，这里只介绍常用的

了解更多，请移步 http://www.rabbitmq.com/tutorials/amqp-concepts.html