Redis 发布订阅(pub/sub)是一种消息通信模式:发送者(pub)发送消息,订阅者(sub)接收消息。
Redis 客户端可以订阅任意数量的频道。
下图展示了频道 channel1 , 以及订阅这个频道的三个客户端 —— client2 、 client5 和 client1 之间的关系:
当有新消息通过 PUBLISH 命令发送给频道 channel1 时, 这个消息就会被发送给订阅它的三个客户端:
以下实例演示了发布订阅是如何工作的。在我们实例中我们创建了订阅频道名为 redisChat:
redis 127.0.0.1:6379> SUBSCRIBE redisChat
Reading messages... (press Ctrl-C to quit)1) "subscribe"2) "redisChat"3) (integer) 1
现在,我们先重新开启个 redis 客户端,然后在同一个频道 redisChat 发布两次消息,订阅者就能接收到消息。
redis 127.0.0.1:6379> PUBLISH redisChat "Redis is a great caching technique"(integer) 1redis 127.0.0.1:6379> PUBLISH redisChat "Learn redis by runoob.com"(integer) 1# 订阅者的客户端会显示如下消息1) "message"2) "redisChat"3) "Redis is a great caching technique"1) "message"2) "redisChat"3) "Learn redis by runoob.com"
springboot中使用:
PUBLISH和SUBSCRIBE
@Autowired
StringRedisTemplate stringRedisTemplate;
public void pushByUserId(ReceiveMessageDto receiveMessageDto) {
String channel = "xxx.push.service";
String message = gson.toJson(receiveMessageDto);
stringRedisTemplate.convertAndSend(channel, message);
}
@Component
public class RedisMessageListener implements MessageListener {
Gson gson = new Gson();
private static Logger logger = LoggerFactory.getLogger(RedisMessageListener.class);
@Bean
public ChannelTopic topic() {
return new ChannelTopic("xxx.push.service");
}
@Bean
MessageListenerAdapter messageListener() {
return new MessageListenerAdapter(new RedisMessageListener());
}
@Bean
RedisMessageListenerContainer redisContainer(RedisConnectionFactory factory) {
final RedisMessageListenerContainer container = new RedisMessageListenerContainer();
container.setConnectionFactory(factory);
container.addMessageListener(messageListener(), topic());
return container;
}
@Override
public void onMessage(Message message, byte[] pattern) {
logger.info(message.toString());
ReceiveMessageDto receiveMessageDto = gson.fromJson(message.toString(), ReceiveMessageDto.class);
try {
//do something
} catch (Exception ex) {
logger.error(ex.toString());
}
}
使用场景: