【Redis】基于redis实现订阅发布

背景

业务发展过程中，希望做到异步解耦，但是又不想引入MQ中间件，在中小型服务中，就可以考虑使用redis自带的订阅发布来解决这个问题。使用 Redis 实现消息的订阅和发布时，可以通过 Spring Boot 集成 Redis 来方便地实现。

引入redis依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>

配置 Redis

在 application.properties 文件中，添加 Redis 配置：

spring.redis.host=localhost
spring.redis.port=6379

编写代码

1. Redis 配置

   创建一个配置类来配置 Redis 的连接工厂和监听器：

   import org.springframework.context.annotation.Bean;
   import org.springframework.context.annotation.Configuration;
   import org.springframework.data.redis.connection.RedisConnectionFactory;
   import org.springframework.data.redis.listener.ChannelTopic;
   import org.springframework.data.redis.listener.RedisMessageListenerContainer;
   import org.springframework.data.redis.listener.adapter.MessageListenerAdapter;
   import org.springframework.data.redis.core.StringRedisTemplate;
   
   @Configuration
   public class RedisConfig {
   
       @Bean
       public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory,
                                                      MessageListenerAdapter listenerAdapter) {
           RedisMessageListenerContainer container = new RedisMessageListenerContainer();
           container.setConnectionFactory(connectionFactory);
           container.addMessageListener(listenerAdapter, topic());
           return container;
       }
   
       @Bean
       public MessageListenerAdapter listenerAdapter(RedisMessageSubscriber subscriber) {
           return new MessageListenerAdapter(subscriber, "onMessage");
       }
   
       @Bean
       public ChannelTopic topic() {
           return new ChannelTopic("messageQueue");
       }
   
       @Bean
       public StringRedisTemplate template(RedisConnectionFactory connectionFactory) {
           return new StringRedisTemplate(connectionFactory);
       }
   }

2. 创建消息订阅者

   编写一个类来处理收到的消息：

   import org.springframework.stereotype.Service;
   
   @Service
   public class RedisMessageSubscriber {
   
       public void onMessage(String message, String channel) {
           System.out.println("Received message: " + message + " from channel: " + channel);
       }
   }

3. 创建消息发布者

   编写一个发布者通过 Redis 模板发送消息：

   import org.springframework.beans.factory.annotation.Autowired;
   import org.springframework.data.redis.core.StringRedisTemplate;
   import org.springframework.data.redis.listener.ChannelTopic;
   import org.springframework.web.bind.annotation.GetMapping;
   import org.springframework.web.bind.annotation.RequestParam;
   import org.springframework.web.bind.annotation.RestController;
   
   @RestController
   public class MessagePublisher {
   
       @Autowired
       private StringRedisTemplate template;
   
       @Autowired
       private ChannelTopic topic;
   
       @GetMapping("/publish")
       public String publish(@RequestParam String message) {
           template.convertAndSend(topic.getTopic(), message);
           return "Message published: " + message;
       }
   }

如果需要监听多个channel，可以通过RedisConfig中添加新的消息适配器。

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.listener.ChannelTopic;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.data.redis.listener.adapter.MessageListenerAdapter;
import org.springframework.data.redis.core.StringRedisTemplate;

@Configuration
public class RedisConfig {

    @Bean
    public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory,
            MessageListenerAdapter listenerAdapter1,
            MessageListenerAdapter listenerAdapter2) {
        RedisMessageListenerContainer container = new RedisMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        container.addMessageListener(listenerAdapter1, topic1());
        container.addMessageListener(listenerAdapter2, topic2());
        return container;
    }

    @Bean
    public MessageListenerAdapter listenerAdapter1(RedisMessageSubscriber subscriber) {
        return new MessageListenerAdapter(subscriber, "onMessage");
    }

    @Bean
    public MessageListenerAdapter listenerAdapter2(RedisMessageSubscriber subscriber) {
        return new MessageListenerAdapter(subscriber, "onMessage");
    }

    @Bean
    public ChannelTopic topic1() {
        return new ChannelTopic("channelOne");
    }

    @Bean
    public ChannelTopic topic2() {
        return new ChannelTopic("channelTwo");
    }

    @Bean
    public StringRedisTemplate template(RedisConnectionFactory connectionFactory) {
        return new StringRedisTemplate(connectionFactory);
    }
}

同时RedisMessageSubscriber 也可以书写多个来区分不同的业务场景下不同业务处理。