开先建设集团网站,网站的建设可以起到什么作用是什么原因,免费建站的网站有哪些,虚拟空间官网一、前言
Redis提供了数据变化的通知事件#xff0c;可以实时监测key和value的变化#xff0c;客户端可以通过订阅相关的channel来接收这些通知事件#xff0c;然后做相应的自定义处理#xff0c;详细的介绍可以参考官方文档Redis keyspace notifications | Docs
使用Red…一、前言
Redis提供了数据变化的通知事件可以实时监测key和value的变化客户端可以通过订阅相关的channel来接收这些通知事件然后做相应的自定义处理详细的介绍可以参考官方文档Redis keyspace notifications | Docs
使用Redis时可以在配置文件中管理相应的配置默认配置是不开启事件通知的。
############################# Event notification ############################### Redis can notify Pub/Sub clients about events happening in the key space.
# This feature is documented at http://redis.io/topics/notifications
#
# For instance if keyspace events notification is enabled, and a client
# performs a DEL operation on key foo stored in the Database 0, two
# messages will be published via Pub/Sub:
#
# PUBLISH __keyspace0__:foo del
# PUBLISH __keyevent0__:del foo
#
# It is possible to select the events that Redis will notify among a set
# of classes. Every class is identified by a single character:
#
# K Keyspace events, published with __keyspacedb__ prefix.
# E Keyevent events, published with __keyeventdb__ prefix.
# g Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
# $ String commands
# l List commands
# s Set commands
# h Hash commands
# z Sorted set commands
# x Expired events (events generated every time a key expires)
# e Evicted events (events generated when a key is evicted for maxmemory)
# A Alias for g$lshzxe, so that the AKE string means all the events.
#
# The notify-keyspace-events takes as argument a string that is composed
# of zero or multiple characters. The empty string means that notifications
# are disabled.
#
# Example: to enable list and generic events, from the point of view of the
# event name, use:
#
# notify-keyspace-events Elg
#
# Example 2: to get the stream of the expired keys subscribing to channel
# name __keyevent0__:expired use:
#
# notify-keyspace-events Ex
#
# By default all notifications are disabled because most users dont need
# this feature and the feature has some overhead. Note that if you dont
# specify at least one of K or E, no events will be delivered.
notify-keyspace-events
二、整合方案
1、自定义监听事件
该方案是自定义监听器messageListener监听指定的频道__keyevent*表示监听所有事件这种方案比较灵活可以自定义监听的事件频道。但是这种需要redis服务配置开启通知例如配置notify-keyspace-events为AKE表示开启全部事件通知。如果redis配置不正确是不会通知指定事件的。另外如果修改了该配置还需要重启Redis服务所以慎重选择该方式。
redis配置如下
# redis配置开启全部事件通知
notify-keyspace-events AKE 代码部分如下
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.PatternTopic;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.data.redis.listener.adapter.MessageListenerAdapter;Configuration
public class RedisListenerConfig {Beanpublic RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory, MessageListenerAdapter listenerAdapter) {RedisMessageListenerContainer container new RedisMessageListenerContainer();container.setConnectionFactory(connectionFactory);// 订阅一个全部变化事件频道 __keyevent*container.addMessageListener(listenerAdapter, new PatternTopic(__keyevent*));return container;}BeanMessageListenerAdapter listenerAdapter() {// 如果使用自定义方法myHandleMessage就把方法名作为第二个参数添入// return new MessageListenerAdapter(new RedisKeyChangeSubscriber(), myHandleMessage);// 如果不传入第二个参数则会使用默认方法handleMessagereturn new MessageListenerAdapter(new RedisKeyChangeSubscriber());}public static class RedisKeyChangeSubscriber {// 自定义处理方法public void myHandleMessage(String message) {System.out.println(RedisKeyChangeSubscriber Received message: message);// 在这里处理收到的消息}// message对应redis数据的keypublic void handleMessage(String message) {System.out.println(RedisKeyChangeSubscriber Received message: message);// 在这里处理收到的消息}}
}
测试效果
①创建键值对{key1: val1} 2、继承spring boot集成的监听器KeyspaceEventMessageListener
spring官方提供的redis starter依赖包含了事件变化监听器KeyspaceEventMessageListener是个抽象类可以通过继承这个抽象类重写doHandleMessage方法来自定义数据变化的处理逻辑。这种方式不需要关注Redis配置简化了监听事件变化的处理容易上手。没有特别要求的话也推荐使用这种方式。同样的该依赖也提供了redis数据过期事件的监听器KeyExpirationEventMessageListener用于监听redis数据过期的事件使用方法和KeyspaceEventMessageListener大体一致但是KeyExpirationEventMessageListener不是抽象类。
import org.jetbrains.annotations.NotNull;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.Message;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.listener.KeyspaceEventMessageListener;
import org.springframework.data.redis.listener.RedisMessageListenerContainer;
import org.springframework.data.redis.listener.adapter.MessageListenerAdapter;Configuration
public class RedisListenerConfig {Beanpublic RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory) {RedisMessageListenerContainer container new RedisMessageListenerContainer();container.setConnectionFactory(connectionFactory);return container;}BeanRedisKeyChangerHandler redisKeyChangerHandler(RedisMessageListenerContainer container) {return new RedisKeyChangerHandler(container);}public static class RedisKeyChangerHandler extends KeyspaceEventMessageListener {/*** Creates new {link KeyspaceEventMessageListener}.** param listenerContainer must not be {literal null}.*/public RedisKeyChangerHandler(RedisMessageListenerContainer listenerContainer) {super(listenerContainer);}Override// message对应redis数据的keyprotected void doHandleMessage(NotNull Message message) {System.out.println(KeyspaceEventMessageListener Received message: message);}}
}
测试效果同方案一。
