RabbitMQ 進階：三大交換機類型詳解與代碼實戰

RabbitMQ 進階：三大交換機類型詳解與代碼實戰

上一篇介紹了直連隊列模式，但實際生產中生產者不直接發送消息到隊列，而是發送到交換機，由交換機根據路由規則分發到隊列。本文深入講解三種核心交換機類型：Fanout、Direct、Topic。

一、發布/訂閱模式 - Fanout Exchange

廣播模式：消息發送到交換機，綁定該交換機的所有隊列都會收到相同消息。

生產者代碼

public class EmitLog {
    private static final String EXCHANGE_NAME = "logs";
    
    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(EXCHANGE_NAME, "fanout");
        
        for (int i = 0; i < 5; i++) {
            String message = "Hello World" + i;
            channel.basicPublish(EXCHANGE_NAME, "", null, message.getBytes());
            System.out.println("EmitLog Sent '" + message + "'");
        }
        channel.close();
        connection.close();
    }
}

消費者代碼（臨時隊列，自動刪除）

public class ReceiveLogs1 {
    private static final String EXCHANGE_NAME = "logs";
    
    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(EXCHANGE_NAME, "fanout");
        String queueName = channel.queueDeclare().getQueue(); // 隨機隊列名
        channel.queueBind(queueName, EXCHANGE_NAME, "");
        
        System.out.println("ReceiveLogs1 Waiting for messages");
        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("ReceiveLogs1 Received '" + message + "'");
            }
        };
        channel.basicConsume(queueName, true, consumer);
    }
}

二、路由模式 - Direct Exchange

根據 Routing Key 精確匹配路由到指定隊列，支持多消費者分工處理不同級別消息。

生產者：發送不同級別日志

public class RoutingSendDirect {
    private static final String EXCHANGE_NAME = "direct_logs";
    private static final String[] ROUTING_KEYS = {"info", "warning", "error"};
    
    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(EXCHANGE_NAME, "direct");
        
        for (String routingKey : ROUTING_KEYS) {
            String message = "RoutingSendDirect Send the message level:" + routingKey;
            channel.basicPublish(EXCHANGE_NAME, routingKey, null, message.getBytes());
            System.out.println("RoutingSendDirect Send " + routingKey + "':'" + message);
        }
        channel.close();
        connection.close();
    }
}

消費者 1：處理 info 和 warning

public class ReceiveLogsDirect1 {
    private static final String EXCHANGE_NAME = "direct_logs";
    private static final String[] ROUTING_KEYS = {"info", "warning"};
    // ... 綁定多個 routingKey 到同一隊列
}

消費者 2：專門處理 error

public class ReceiveLogsDirect2 {
    private static final String EXCHANGE_NAME = "direct_logs";
    private static final String[] ROUTING_KEYS = {"error"};
    // ... 只綁定 error routingKey
}

三、主題模式 - Topic Exchange

支持通配符模糊匹配：* 匹配單個詞，# 匹配零個或多個詞。

路由鍵示例

• quick.orange.rabbit
• lazy.orange.elephant
• quick.orange.fox

消費者綁定模式

• *.orange.*：匹配中間為 orange 的所有路由
• *.*.rabbit：匹配最後為 rabbit 的三段式路由
• lazy.#：匹配以 lazy 開頭的所有路由

核心區別總結

掌握三種交換機模式，能靈活設計消息路由拓撲，滿足不同業務場景需求。