前言

项目中需要监听redis的一些事件比如键删除，修改，过期等。过期事件网上有很多例子可以参考，但修改或删除事件却很少。因为redis支持发布订阅所以其他的事件类型应该也是能实现的，通过过期事件监听结合上文键空间通知，我整理了相关代码，希望帮助需要的人快速解决问题。

代码实践

网上示例的失效事件监听代码

import com.alibaba.fastjson.JSONObject;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.listener.KeyExpirationEventMessageListener;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.stereotype.Component;

import java.util.Date;

@Component
public class RedisKeyExpirationListener extends KeyExpirationEventMessageListener {

    public RedisKeyExpirationListener(RedisMessageListenerContainer listenerContainer) {
        super(listenerContainer);
    }

    /**
     * 针对redis数据失效事件，进行数据处理
     * @param message message.toString()获取失效的key
     * @param pattern
     */
    @Override
    public void onMessage(Message message, byte[] pattern) {
        String expiredKey = message.toString();
        // 获得key之后可以做自己的逻辑操作
        }
    }
}

可以看到继承了KeyExpirationEventMessageListener ，这是spring框架已经集成实现的。

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.springframework.data.redis.listener;

import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.core.RedisKeyExpiredEvent;
import org.springframework.lang.Nullable;

public class KeyExpirationEventMessageListener extends KeyspaceEventMessageListener implements ApplicationEventPublisherAware {
    private static final Topic KEYEVENT_EXPIRED_TOPIC = new PatternTopic("__keyevent@*__:expired");
    @Nullable
    private ApplicationEventPublisher publisher;

    public KeyExpirationEventMessageListener(RedisMessageListenerContainer listenerContainer) {
        super(listenerContainer);
    }

    protected void doRegister(RedisMessageListenerContainer listenerContainer) {
        listenerContainer.addMessageListener(this, KEYEVENT_EXPIRED_TOPIC);
    }

    protected void doHandleMessage(Message message) {
        this.publishEvent(new RedisKeyExpiredEvent(message.getBody()));
    }

    protected void publishEvent(RedisKeyExpiredEvent event) {
        if (this.publisher != null) {
            this.publisher.publishEvent(event);
        }

    }

    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.publisher = applicationEventPublisher;
    }
}

其他的比如删除事件他没有实现，那我就考虑模仿spring也写个这样的Listener。

简单了解redis键空间通知是怎么回事：
参考文档http://redisdoc.com/topic/notification.html

键空间通知，所有通知以 keyspace@<db> 为前缀
键事件通知，所有通知以 keyevent@<db> 为前缀
所有命令都只在键真的被改动了之后，才会产生通知，比如删除foo会产生
键空间通知
"pmessage","__ key__:","__ keyspace@0__:foo","set"
和键事件通知
"pmessage","__ key__:","__ keyevent@0__:set","foo"

如果要监听某个key的执行了什么操作，就订阅 keyspace@<db>，监听某种操作动了哪些key，就订阅keyevent@<db>。
这里我们需要监听哪些键被删除了，所以要监听删除动作"__ keyevent@0__:del"

对比上文spring写的listener有这么一句
private static final Topic KEYEVENT_EXPIRED_TOPIC = new PatternTopic("__keyevent@*__:expired");
其他都是模式化的代码，只要修改对应的topic类型就能实现监听了。

import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.core.RedisKeyExpiredEvent;
import org.springframework.data.redis.listener.KeyspaceEventMessageListener;
import org.springframework.data.redis.listener.PatternTopic;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.data.redis.listener.Topic;
import org.springframework.lang.Nullable;

public class KeyDeleteEventMessageListener extends KeyspaceEventMessageListener implements ApplicationEventPublisherAware {
    private static final Topic KEYEVENT_DELETE_TOPIC = new PatternTopic("__keyevent@*__:del");
    @Nullable
    private ApplicationEventPublisher publisher;

    public KeyDeleteEventMessageListener(RedisMessageListenerContainer listenerContainer) {
        super(listenerContainer);
    }

    protected void doRegister(RedisMessageListenerContainer listenerContainer) {
        listenerContainer.addMessageListener(this, KEYEVENT_DELETE_TOPIC);
    }

    protected void doHandleMessage(Message message) {
        this.publishEvent(new RedisKeyExpiredEvent(message.getBody()));
    }

    protected void publishEvent(RedisKeyExpiredEvent event) {
        if (this.publisher != null) {
            this.publisher.publishEvent(event);
        }

    }

    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.publisher = applicationEventPublisher;
    }
}

类似的新增和修改也一样

package cn.fatri.jarvis.device.shadow.listener;

import org.springframework.context.ApplicationEventPublisher;
import org.springframework.context.ApplicationEventPublisherAware;
import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.core.RedisKeyExpiredEvent;
import org.springframework.data.redis.listener.KeyspaceEventMessageListener;
import org.springframework.data.redis.listener.PatternTopic;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.data.redis.listener.Topic;
import org.springframework.lang.Nullable;

public class KeyUpdateEventMessageListener extends KeyspaceEventMessageListener implements ApplicationEventPublisherAware {
    private static final Topic KEYEVENT_DELETE_TOPIC = new PatternTopic("__keyevent@*__:set");
    @Nullable
    private ApplicationEventPublisher publisher;

    public KeyUpdateEventMessageListener(RedisMessageListenerContainer listenerContainer) {
        super(listenerContainer);
    }

    protected void doRegister(RedisMessageListenerContainer listenerContainer) {
        listenerContainer.addMessageListener(this, KEYEVENT_DELETE_TOPIC);
    }

    protected void doHandleMessage(Message message) {
        this.publishEvent(new RedisKeyExpiredEvent(message.getBody()));
    }

    protected void publishEvent(RedisKeyExpiredEvent event) {
        if (this.publisher != null) {
            this.publisher.publishEvent(event);
        }

    }

    public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
        this.publisher = applicationEventPublisher;
    }
}

我们同样继承这些类就能拿到监听的message了

import lombok.extern.slf4j.Slf4j;
import org.apache.commons.io.FileUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.stereotype.Component;

import java.io.File;
import java.io.IOException;
import java.util.stream.Collectors;

@Component
@Slf4j
public class RedisKeyDeleteListener extends KeyDeleteEventMessageListener {

    public RedisKeyDeleteListener(RedisMessageListenerContainer listenerContainer) {
        super(listenerContainer);
    }

    /**
     * 针对redis数据删除事件，进行数据处理
     * @param message message.toString()获取失效的key
     * @param pattern
     */
    @Override
    public void onMessage(Message message, byte[] pattern) {
        String deleteKey = message.toString();
        // ......
        }
    }
}