利用KeyExpirationEventMessageListener实现redis的key失效监听。

在使用redis时，所有的key都要设置过期时间，过期之后，redis就会把对应的key清除掉。此方法可以监听redis的key失效，在失效时做一些逻辑处理。话不多说，上代码。
依赖:

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

实现:

import com.upbim.twin.park.common.constans.Constants;
import com.upbim.twin.park.server.strategy.PushMessageStrategyContext;
import lombok.extern.slf4j.Slf4j;
import org.slf4j.MDC;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.data.redis.RedisProperties;
import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.listener.KeyExpirationEventMessageListener;
import org.springframework.data.redis.listener.PatternTopic;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.data.redis.listener.Topic;
import org.springframework.stereotype.Service;

import java.util.UUID;

import static com.upbim.twin.park.common.constans.Constants.TRACE_ID;
@Slf4j
@Service
public class AgentOrderRedisKeyExpiredListener extends KeyExpirationEventMessageListener {

    @Autowired
    private PushMessageStrategyContext pushMessageStrategyContext;
    @Autowired
    private RedisProperties redisProperties;

    /**
     * Creates new  MessageListener for {@code __keyevent@*__:expired} messages.
     *
     * @param listenerContainer must not be {@literal null}.
     */
    public AgentOrderRedisKeyExpiredListener(RedisMessageListenerContainer listenerContainer) {
        super(listenerContainer);
    }

    @Override
    protected void doRegister(RedisMessageListenerContainer listenerContainer) {

        // 只监听指定redis数据库的key过期事件
        Topic topic = new PatternTopic(String.format("__keyevent@%s__:expired", redisProperties.getDatabase()));
        listenerContainer.addMessageListener(this, topic);
    }

    @Override
    protected void doHandleMessage(Message message) {

        // 订阅的topic： new String(message.getChannel(), UTF_8) --->  "__keyevent@0__:expired"
        // 触发key失效发布的key：new String(message.getBody(), UTF_8) --->  "demoKey"
        MDC.put(TRACE_ID, UUID.randomUUID().toString());
        try {
            log.info(String.format("Redis key expired event:%s", message.toString()));

            String beanName = message.toString().split(Constants.COLON)[Constants.ONE];
            pushMessageStrategyContext.handleRedisExpireKey(beanName, message.toString());
            super.doHandleMessage(message);
        } finally {

            MDC.clear();
        }
    }

}

监听处理类

package com.upbim.twin.park.server.strategy;

import com.google.common.collect.Maps;
import com.upbim.twin.park.server.strategy.nozzle.PushMessageStrategy;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import java.util.Map;
import java.util.Objects;

@Slf4j
@Component
public class PushMessageStrategyContext {

    /**
     * 使用线程安全的ConcurrentHashMap存储所有实现Strategy接口的Bean
     * key:beanName
     * value：实现Strategy接口Bean
     */
    private final Map<String, PushMessageStrategy> strategyMap = Maps.newConcurrentMap();

    /**
     * 注入所有实现了Strategy接口的Bean
     *
     * @param strategyMap the strategy map
     */
    @Autowired
    public PushMessageStrategyContext(Map<String, PushMessageStrategy> strategyMap) {
        strategyMap.forEach(this.strategyMap::put);
    }

    /**
     * 策略监听redis所有过期key
     *
     * @param beanName        the bean name
     * @param redisInvalidKey the redis invalid key
     * @return
     */
    public void handleRedisExpireKey(String beanName, String redisInvalidKey) {

        if (Objects.nonNull(strategyMap.get(beanName))) {
            strategyMap.get(beanName).handleRedisExpireKey(redisInvalidKey);
        } else {
            log.warn("找不到对应的策略：{}", strategyMap.get(beanName));
        }
    }

}

public interface PushMessageStrategy {
  void handleRedisExpireKey(String redisInvalidKey);
}

大家在使用的时候，可以针对自己不同的场景，实现PushMessageStrategy 接口，重写handleRedisExpireKey方法。在方法中处理不同的逻辑。

首先，在redis’中有key失效过期时，AgentOrderRedisKeyExpiredListener 监听到redis实现，会执行doHandleMessage方法，方法中会调用PushMessageStrategyContext 的获取不同策略的Bean，进行业务操作。至此，监听redis中key失效完成。欢迎大家点赞收藏使用。