前言

RabbitMQ是工作中经常使用的一个开源消息队列，它是通过Erlang语言来开发的，RabbitMQ中有一个非常常见且重要的概念叫交换器（Exchange），所有生产者提交的消息都是通过Exchange进行接收，然后通过特定的路由策略转发对特定的队列（Queue）中，然后消费者通过绑定特定的队列，将队列中的信息进行消费处理。我们如果是通过RabbitMQ的客户端来进行创建Exchange的话，一定需要你选择一个特定的Exchange类型的，这个时候如果不了解每一种类型的特性，就很容易选择错误，造成整个业务流程中的异常，接下来我们就来梳理一下Exchange对应的四种类型：direct、fanout、headers、topic分别的特点和使用场景

消息接受与发送入门

在详细梳理Exchange之前，我们先简单的了解看一下RabbitMq通过最简单的方式，来实现针对一条消息的发送与接手，在这个代码运行前，确保已经在本地安装了一个可以正常运行的RabbitMq，最好还有一个还有了一个可以RabbitMq的管理后台，用来更加方便的查看当前管理和维护的Exchange、Queue等信息，如下图所示：

依赖配置

如果你是采用maven来进行代码依赖管理的话，首先需要将RabbitMq的依赖的pom文件加入到项目中，我的代码使用的是最新版的 5.11.0，如下图所示


<dependency>

<groupId>com.rabbitmq</groupId>

<artifactId>amqp-client</artifactId>

<version>5.11.0</version>

</dependency>

发送消息到指定队列（Queue）


import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import java.nio.charset.StandardCharsets;

public class PublishTest {

public static final String TEST_QUEUE = "test-queue";

public static void main(String[] args) {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

try (Connection connection = factory.newConnection();

Channel channel = connection.createChannel()) {

channel.queueDeclare(TEST_QUEUE, false, false, false, null);

String message = "你好，朋友 - 1 ";

channel.basicPublish("",TEST_QUEUE,null, message.getBytes(StandardCharsets.UTF_8));

System.out.println(" 发送消息 : " + message);

} catch (Exception e) {

e.printStackTrace();

}

}

}

消费指定队列消息


import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import com.rabbitmq.client.DeliverCallback;

import java.nio.charset.StandardCharsets;

public class ConsumerTest {

public static void main(String[] args) throws Exception{

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

Connection connection = factory.newConnection() ;

Channel channel = connection.createChannel();

System.out.println(" 等待消息到达，通过 CTRL+C 关闭");

DeliverCallback deliverCallback = (consumerTag, delivery) -> {

String message = new String(delivery.getBody(), StandardCharsets.UTF_8);

System.out.println(" 接收到的消息 ： " + message );

};

channel.basicConsume(PublishTest.TEST_QUEUE, true, deliverCallback, consumerTag -> {

});

}

}

Exchange类型介绍

direct

Exchange默认的类型就是direct，该类型的Exchange消息分发机制非常简单，需要和routingKey配合使用，首先在配置阶段，direct类型的Exchange通过一个rountingKey和Queue进行绑定，绑定完成后，消息通过使用Exchange名称和rountingKey进行发送，消息到达RabbitMq服务器后，rountingKey需要和Queue绑定的rountingKey完全相同才会进行消息的路由，路由到对应的Queue，流程如下图所示：

null

代码功能验证
发送Direct类型Exchange消息

import com.rabbitmq.client.BuiltinExchangeType;

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import java.nio.charset.StandardCharsets;

public class DirectExchange {

public static final String DIRECT_EXCHANGE_NAME = "direct-exchange-test";

public static final String ROUTING_KEY_A = "A.D";

public static final String ROUTING_KEY_B = "B.D";

public static final String ROUTING_KEY_C = "C";

public static final String ROUTING_KEY_D = "D";

public static final String ROUTING_KEY_E = "A.*";

public static final String MESSAGE_A = "你好，朋友-A";

public static final String MESSAGE_B = "你好，朋友-B";

public static final String MESSAGE_C = "你好，朋友-C";

public static final String MESSAGE_D = "你好，朋友-D";

public static final String MESSAGE_E = "你好，朋友-E";

public static void main(String[] args) {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

try (Connection connection = factory.newConnection();

Channel channel = connection.createChannel()) {

channel.exchangeDeclare(DIRECT_EXCHANGE_NAME, BuiltinExchangeType.DIRECT);

channel.basicPublish(DIRECT_EXCHANGE_NAME, ROUTING_KEY_A, null, MESSAGE_A.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(DIRECT_EXCHANGE_NAME, ROUTING_KEY_B, null, MESSAGE_B.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(DIRECT_EXCHANGE_NAME, ROUTING_KEY_C, null, MESSAGE_C.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(DIRECT_EXCHANGE_NAME, ROUTING_KEY_D, null, MESSAGE_D.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(DIRECT_EXCHANGE_NAME, ROUTING_KEY_E, null, MESSAGE_E.getBytes(StandardCharsets.UTF_8));

} catch (Exception e) {

e.printStackTrace();

}

}

}
消费Direct类型Exchange消息

import com.example.druiddemo.publisher.DirectExchange;

import com.rabbitmq.client.*;

import java.nio.charset.StandardCharsets;

public class DirectConsumerTest {

public static final String DIRECT_QUEUE_NAME = "direct-queue-test";

public static final String BINDING_KEY_A = "A.*";

public static final String BINDING_KEY_B = "*.D";

public static final String BINDING_KEY_C = "C";

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

Connection connection = factory.newConnection() ;

Channel channel = connection.createChannel();

channel.queueDeclare(DIRECT_QUEUE_NAME, false, false, false, null);

channel.queueBind(DIRECT_QUEUE_NAME, DirectExchange.DIRECT_EXCHANGE_NAME, BINDING_KEY_A);

channel.queueBind(DIRECT_QUEUE_NAME, DirectExchange.DIRECT_EXCHANGE_NAME, BINDING_KEY_B);

channel.queueBind(DIRECT_QUEUE_NAME, DirectExchange.DIRECT_EXCHANGE_NAME, BINDING_KEY_C);

System.out.println(" 等待消息到达，通过 CTRL+C 关闭");

DeliverCallback deliverCallback = (consumerTag, delivery) -> {

String message = new String(delivery.getBody(), StandardCharsets.UTF_8);

System.out.println(" 接收到的消息 ： " + message );

};

channel.basicConsume(DIRECT_QUEUE_NAME, true, deliverCallback, consumerTag -> {

});

}

}

fanout

Exchange中的fanout类型是我们一般使用的偏少的一种类型，采用的是广播的形式来进行消息转发处理，同时该模式下的不需要使用RountingKey，只要是与该Exchange绑定的所有的队列均可以收到发送的消息，该模式主要用于当某个事件发生是对相关业务的通知，这样只要想要知道该事件的所有业务只需要绑定到这个Exchange即可平等收到转发的消息

null

代码功能验证
发送Fanout类型Exchange消息

import com.rabbitmq.client.BuiltinExchangeType;

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import java.nio.charset.StandardCharsets;

public class FanoutExchange {

public static final String FANOUT_EXCHANGE_NAME = "fanout-exchange-test";

public static final String MESSAGE_A = "你好，朋友-A";

public static final String MESSAGE_B = "你好，朋友-B";

public static final String MESSAGE_C = "你好，朋友-C";

public static final String MESSAGE_D = "你好，朋友-D";

public static final String MESSAGE_E = "你好，朋友-E";

public static void main(String[] args) {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

try (Connection connection = factory.newConnection();

Channel channel = connection.createChannel()) {

channel.exchangeDeclare(FANOUT_EXCHANGE_NAME, BuiltinExchangeType.FANOUT);

channel.basicPublish(FANOUT_EXCHANGE_NAME, "", null, MESSAGE_A.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(FANOUT_EXCHANGE_NAME, "", null, MESSAGE_B.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(FANOUT_EXCHANGE_NAME, "", null, MESSAGE_C.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(FANOUT_EXCHANGE_NAME, "", null, MESSAGE_D.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(FANOUT_EXCHANGE_NAME, "", null, MESSAGE_E.getBytes(StandardCharsets.UTF_8));

} catch (Exception e) {

e.printStackTrace();

}

}

}
消费Fanout类型Exchange消息

import com.example.druiddemo.publisher.FanoutExchange;

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import com.rabbitmq.client.DeliverCallback;

import java.nio.charset.StandardCharsets;

public class FanoutConsumerTest {

public static final String FANOUT_QUEUE_NAME = "fanout-queue-test";

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

Connection connection = factory.newConnection() ;

Channel channel = connection.createChannel();

channel.queueDeclare(FANOUT_QUEUE_NAME, false, false, false, null);

channel.queueBind(FANOUT_QUEUE_NAME, FanoutExchange.FANOUT_EXCHANGE_NAME, "");

System.out.println("fanout-queue-test 等待消息到达，通过 CTRL+C 关闭");

DeliverCallback deliverCallback = (consumerTag, delivery) -> {

String message = new String(delivery.getBody(), StandardCharsets.UTF_8);

System.out.println("fanout-queue-test 接收到的消息 ： " + message );

};

channel.basicConsume(FANOUT_QUEUE_NAME, true, deliverCallback, consumerTag -> {

});

}

}
消费Fanout类型Exchange消息

import com.example.druiddemo.publisher.FanoutExchange;

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import com.rabbitmq.client.DeliverCallback;

import java.nio.charset.StandardCharsets;

public class FanoutConsumerTwoTest {

public static final String FANOUT_QUEUE_NAME_COPY = "fanout-queue-test-copy";

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

Connection connection = factory.newConnection() ;

Channel channel = connection.createChannel();

channel.queueDeclare(FANOUT_QUEUE_NAME_COPY, false, false, false, null);

channel.queueBind(FANOUT_QUEUE_NAME_COPY, FanoutExchange.FANOUT_EXCHANGE_NAME, "");

System.out.println("fanout-queue-test-copy 等待消息到达，通过 CTRL+C 关闭");

DeliverCallback deliverCallback = (consumerTag, delivery) -> {

String message = new String(delivery.getBody(), StandardCharsets.UTF_8);

System.out.println("fanout-queue-test-copy 接收到的消息 ： " + message );

};

channel.basicConsume(FANOUT_QUEUE_NAME_COPY, true, deliverCallback, consumerTag -> {

});

}

}

headers

该类型的Exchange是我们在日常开发中使用的最少的一种类型，该类型的Exhange转发消息并不是通过RountingKey来进行路由，而是通过它的绑定参数（Arguments）来进行转发的，它的配置位置是配置信息的headers中，该模式下的消息转发路径如下：

null

代码功能验证
发送Headers类型Exchange消息

import com.rabbitmq.client.*;

import java.nio.charset.StandardCharsets;

import java.util.Hashtable;

import java.util.Map;

public class HeadersExchange {

public static final String HEADERS_EXCHANGE_NAME = "headers-exchange-test";

public static final String MESSAGE_A = "你好，朋友-A";

public static final String MESSAGE_B = "你好，朋友-B";

public static final String MESSAGE_C = "你好，朋友-C";

public static void main(String[] args) {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

try (Connection connection = factory.newConnection();

Channel channel = connection.createChannel()) {

channel.exchangeDeclare(HEADERS_EXCHANGE_NAME, BuiltinExchangeType.HEADERS);

Map<String, Object> headersOne = new Hashtable<>();

headersOne.put("t", "s");

headersOne.put("m", "k");

AMQP.BasicProperties basicProperties = new AMQP.BasicProperties().builder().headers(headersOne).build();

System.out.println(basicProperties.toString());

channel.basicPublish(HEADERS_EXCHANGE_NAME, "", basicProperties, MESSAGE_A.getBytes(StandardCharsets.UTF_8));

Map<String, Object> headersTwo = new Hashtable<>();

headersTwo.put("t", "s");

AMQP.BasicProperties basicPropertiesTwo = new AMQP.BasicProperties().builder().headers(headersTwo).build();

System.out.println(basicPropertiesTwo.toString());

channel.basicPublish(HEADERS_EXCHANGE_NAME, "", basicPropertiesTwo, MESSAGE_B.getBytes(StandardCharsets.UTF_8));

Map<String, Object> headersThree = new Hashtable<>();

headersThree.put("m", "k");

AMQP.BasicProperties basicPropertiesThree = new AMQP.BasicProperties().builder().headers(headersThree).build();

System.out.println(basicPropertiesThree.toString());

channel.basicPublish(HEADERS_EXCHANGE_NAME, "", basicPropertiesThree, MESSAGE_C.getBytes(StandardCharsets.UTF_8));

} catch (Exception e) {

e.printStackTrace();

}

}

}
消费Headers类型Exchange消息

import com.example.druiddemo.publisher.HeadersExchange;

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import com.rabbitmq.client.DeliverCallback;

import java.nio.charset.StandardCharsets;

import java.util.Hashtable;

import java.util.Map;

public class HeadersConsumerTest {

public static final String HEADERS_QUEUE_NAME = "headers-queue-test";

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

Connection connection = factory.newConnection() ;

Channel channel = connection.createChannel();

channel.queueDeclare(HEADERS_QUEUE_NAME, false, false, false, null);

Map<String, Object> headers = new Hashtable<>();

headers.put("t", "s");

headers.put("m", "k");

headers.put("x-match", "all");

channel.queueBind(HEADERS_QUEUE_NAME, HeadersExchange.HEADERS_EXCHANGE_NAME, "", headers);

System.out.println("headers-queue-test 等待消息到达，通过 CTRL+C 关闭");

DeliverCallback deliverCallback = (consumerTag, delivery) -> {

String message = new String(delivery.getBody(), StandardCharsets.UTF_8);

System.out.println("headers-queue-test 接收到的消息 ： " + message );

};

channel.basicConsume(HEADERS_QUEUE_NAME, true, deliverCallback, consumerTag -> {

});

}

}
消费Headers类型Exchange消息

import com.example.druiddemo.publisher.HeadersExchange;

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import com.rabbitmq.client.DeliverCallback;

import java.nio.charset.StandardCharsets;

import java.util.Hashtable;

import java.util.Map;

public class HeadersConsumerTwoTest {

public static final String HEADERS_QUEUE_NAME = "headers-queue-test-two";

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

Connection connection = factory.newConnection() ;

Channel channel = connection.createChannel();

channel.queueDeclare(HEADERS_QUEUE_NAME, false, false, false, null);

Map<String, Object> headers = new Hashtable<>();

headers.put("t", "s");

headers.put("m", "k");

headers.put("x-match", "any");

channel.queueBind(HEADERS_QUEUE_NAME, HeadersExchange.HEADERS_EXCHANGE_NAME, "", headers);

System.out.println("headers-queue-test-two 等待消息到达，通过 CTRL+C 关闭");

DeliverCallback deliverCallback = (consumerTag, delivery) -> {

String message = new String(delivery.getBody(), StandardCharsets.UTF_8);

System.out.println("headers-queue-test-two 接收到的消息 ： " + message );

};

channel.basicConsume(HEADERS_QUEUE_NAME, true, deliverCallback, consumerTag -> {

});

}

}
消费Headers类型Exchange消息

import com.example.druiddemo.publisher.HeadersExchange;

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import com.rabbitmq.client.DeliverCallback;

import java.nio.charset.StandardCharsets;

import java.util.Hashtable;

import java.util.Map;

public class HeadersConsumerThreeTest {

public static final String HEADERS_QUEUE_NAME = "headers-queue-test-three";

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

Connection connection = factory.newConnection() ;

Channel channel = connection.createChannel();

channel.queueDeclare(HEADERS_QUEUE_NAME, false, false, false, null);

Map<String, Object> headers = new Hashtable<>();

headers.put("m", "k");

headers.put("x-match", "any");

channel.queueBind(HEADERS_QUEUE_NAME, HeadersExchange.HEADERS_EXCHANGE_NAME, "", headers);

System.out.println("headers-queue-test-two 等待消息到达，通过 CTRL+C 关闭");

DeliverCallback deliverCallback = (consumerTag, delivery) -> {

String message = new String(delivery.getBody(), StandardCharsets.UTF_8);

System.out.println("headers-queue-test-two 接收到的消息 ： " + message );

};

channel.basicConsume(HEADERS_QUEUE_NAME, true, deliverCallback, consumerTag -> {

});

}

}

topic

topic类型的Exchange必须要配置一个RountingKey，该RountingKey由字符组成，通过dots（也就是 . ）来进行分割，RountingKey可以是任意字符来组成，但是上线不可以超过 255 bytes；Queue通过Binding Key来将Exchange与之绑定，Exchange下RountingKey与Binding Key相匹配的消息被发送到对应的绑定的Queue中，然后消息被当前Queue的消费者进行消费处理，在Binding Key中有两个非常常用并且特殊的字符需要注意：

  • *：与RountingKey进行匹配时，可以精确的代替一个字符

  • #：与RountingKey进行匹配时，可以代替0个或多个字符

null

代码功能验证
发送Topic类型Exchange消息

import com.rabbitmq.client.BuiltinExchangeType;

import com.rabbitmq.client.Channel;

import com.rabbitmq.client.Connection;

import com.rabbitmq.client.ConnectionFactory;

import java.nio.charset.StandardCharsets;

public class TopicExchange {

public static final String TOPIC_EXCHANGE_NAME = "topic-exchange-test";

public static final String ROUTING_KEY_A = "A.D";

public static final String ROUTING_KEY_B = "B.D";

public static final String ROUTING_KEY_C = "C";

public static final String ROUTING_KEY_D = "D";

public static final String MESSAGE_A = "你好，朋友-A";

public static final String MESSAGE_B = "你好，朋友-B";

public static final String MESSAGE_C = "你好，朋友-C";

public static final String MESSAGE_D = "你好，朋友-D";

public static void main(String[] args) {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

try (Connection connection = factory.newConnection();

Channel channel = connection.createChannel()) {

channel.exchangeDeclare(TOPIC_EXCHANGE_NAME, BuiltinExchangeType.TOPIC);

channel.basicPublish(TOPIC_EXCHANGE_NAME, ROUTING_KEY_A, null, MESSAGE_A.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(TOPIC_EXCHANGE_NAME, ROUTING_KEY_B, null, MESSAGE_B.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(TOPIC_EXCHANGE_NAME, ROUTING_KEY_C, null, MESSAGE_C.getBytes(StandardCharsets.UTF_8));

channel.basicPublish(TOPIC_EXCHANGE_NAME, ROUTING_KEY_D, null, MESSAGE_D.getBytes(StandardCharsets.UTF_8));

} catch (Exception e) {

e.printStackTrace();

}

}

}
消费Topic类型Exchange消息

import com.example.druiddemo.publisher.TopicExchange;

import com.rabbitmq.client.*;

import java.nio.charset.StandardCharsets;

public class TopicConsumerTest {

public static final String TOPIC_QUEUE_NAME = "topic-queue-test";

public static final String BINDING_KEY_A = "A.*";

public static final String BINDING_KEY_B = "*.D";

public static final String BINDING_KEY_C = "C";

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();

factory.setHost("localhost");

Connection connection = factory.newConnection() ;

Channel channel = connection.createChannel();

channel.exchangeDeclare(TopicExchange.TOPIC_EXCHANGE_NAME, BuiltinExchangeType.TOPIC);

channel.queueDeclare(TOPIC_QUEUE_NAME, false, false, false, null);

channel.queueBind(TOPIC_QUEUE_NAME, TopicExchange.TOPIC_EXCHANGE_NAME, BINDING_KEY_C);

System.out.println(" 等待消息到达，通过 CTRL+C 关闭");

DeliverCallback deliverCallback = (consumerTag, delivery) -> {

String message = new String(delivery.getBody(), StandardCharsets.UTF_8);

System.out.println(" 接收到的消息 ： " + message );

};

channel.basicConsume(TOPIC_QUEUE_NAME, true, deliverCallback, consumerTag -> {

});

}

}

总结

通过上面的介绍，我们已经清楚的了解了每一种Exchange类型的特点和他们的使用场景，在我们的日常使用中一定要先明确我们的使用的特点，然后再去根据实际情况去选择最合适的Exchange来进行创建和使用，这样才是最为高效和合理的，其实在上面的topic类型的Exchange是可以通过一些变通来实现direct类型和fanout类型的Exhange的：如果topic类型的Exchange绑定的Queue的绑定Key是 “#” ，则该Exhange下的所有消息都会转发到该Queue；如果topic类型的Exchange绑定的Queue的绑定Key中不包含 "* " 或 “#”，则该Exchange和direct类型的使用场景就一致了

弦外音

这个地方主要分析的是RabbitMq的一些重要组成部分的详细的使用，如果你想要深入的理解这里的每一种类型的使用，还是需要亲自在编写相关的代码，然后进行相关的类型的运行和实际效果的观察，如果你的电脑还没有安装RabbitMq，那么你可以查看这篇文章，这里有安装的完整步骤和安装过程中容易碰到的几个异常，希望可以帮助你更好的使用RabbitMq：https://community.jiguang.cn/article/465057