Topic 交换机

Topic交换机通过通配符模式匹配路由键，实现基于主题结构的灵活消息路由。

定义

Topic交换机将消息路由到绑定队列中路由键模式匹配的队列。支持通配符*（匹配一个单词）和#（匹配零个或多个单词），路由键以点号.分隔形成层级结构。

核心机制

通配符规则

• *：匹配一个单词段，如stock.*匹配stock.usd但不匹配stock.usd.nyse
• #：匹配零个或多个单词段，如stock.#匹配stock.usd、stock.usd.nyse
• 路由键格式：以点号分隔的单词序列，如order.created.success

声明与绑定示例

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

public class TopicExchangeExample {
    private static final String EXCHANGE_NAME = "topic_orders";

    public static void main(String[] args) throws Exception {
        ConnectionFactory factory = new ConnectionFactory();
        factory.setHost("localhost");
        
        try (Connection connection = factory.newConnection();
             Channel channel = connection.createChannel()) {
            
            // 声明Topic交换机
            channel.exchangeDeclare(EXCHANGE_NAME, "topic", true);
            
            // 声明队列
            channel.queueDeclare("queue_all_orders", true, false, false, null);
            channel.queueDeclare("queue_us_orders", true, false, false, null);
            channel.queueDeclare("queue_critical", true, false, false, null);
            
            // 绑定队列与通配符路由键
            // 接收所有订单消息
            channel.queueBind("queue_all_orders", EXCHANGE_NAME, "order.*");
            // 仅接收美国订单
            channel.queueBind("queue_us_orders", EXCHANGE_NAME, "order.us.*");
            // 接收所有紧急订单
            channel.queueBind("queue_critical", EXCHANGE_NAME, "#.critical");
            
            // 发布消息
            String[] routingKeys = {
                "order.us.created",
                "order.eu.created", 
                "order.us.critical",
                "payment.critical.failed"
            };
            
            for (String routingKey : routingKeys) {
                String message = "Message with routing key: " + routingKey;
                channel.basicPublish(EXCHANGE_NAME, routingKey, null, 
                        message.getBytes("UTF-8"));
                System.out.println("Sent: " + routingKey);
            }
        }
    }
}

消费者示例

import com.rabbitmq.client.*;
import java.io.IOException;

public class TopicConsumer {
    private static final String EXCHANGE_NAME = "topic_orders";
    private static final String QUEUE_NAME = "queue_us_orders";

    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, "topic", true);
        channel.queueDeclare(QUEUE_NAME, true, false, false, null);
        
        // 绑定通配符路由键
        channel.queueBind(QUEUE_NAME, EXCHANGE_NAME, "order.us.*");
        
        System.out.println("Waiting for US order messages...");
        
        DeliverCallback deliverCallback = (consumerTag, delivery) -> {
            String message = new String(delivery.getBody(), "UTF-8");
            String routingKey = delivery.getEnvelope().getRoutingKey();
            System.out.println("Received [" + routingKey + "]: " + message);
            channel.basicAck(delivery.getEnvelope().getDeliveryTag(), false);
        };
        
        channel.basicConsume(QUEUE_NAME, false, deliverCallback, consumerTag -> {});
    }
}

注意事项

• 路由键单词段数建议不超过10个，避免模式匹配性能下降
• #通配符匹配零个或多个单词，#.critical可匹配critical本身
• Topic交换机匹配性能略低于Direct交换机，需权衡灵活性与性能
• 路由键设计应具有明确层级结构，如区域.业务.操作.状态
• 不支持正则表达式，仅支持*和#两种通配符

要点总结

• Topic交换机通过*和#通配符实现灵活的模式匹配路由
• *匹配一个单词段，#匹配零个或多个单词段
• 适用于基于主题分类、多条件过滤的消息路由场景
• 路由键设计应遵循层级结构规范，便于通配符匹配
• 性能略低于Direct交换机，但提供更高的路由灵活性

文章存放路径：D:\git2\jwdev\articles\RABBITMQ\进阶\交换机类型详解\Topic 交换机.md