redis 清空缓存_Redis缓存

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我是靠谱客的博主内向毛巾，最近开发中收集的这篇文章主要介绍redis 清空缓存_Redis缓存，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

一:缓存的概念

1.1. 什么是缓存(cache)

1) cache是高速缓冲存储器，主要解决频繁使用的数据快速访问的问题。

2) 如果两个硬件或者软件之间的速度存在较大差异，主要使用缓存协调两者的速度差异

1.2. 缓存的分类

1) 操作系统磁盘缓存：减少磁盘机械操作。

2) 数据库缓存：减少应用程序对数据库服务器的IO操作。

3) web服务器缓存：减轻web服务器的压力。

4) 浏览器缓存：访问速度快，提升用户体验度，减轻网站压力。

二.redis(单机版)实现mybatis的二级缓存

2.1. 环境准备

使用maven搭建一套ssm框架，并创建测试类查询emp表。测试代码如下：

/**

* 不使用缓存的查询时间

public static void main(String[] args) {

ApplicationContext ac =new ClassPathXmlApplicationContext("applicationContext.xml");

EmpMapper empMapper=(EmpMapper) ac.getBean("empMapper");

Long begin=System.currentTimeMillis();

empMapper.findAllEmp();

Long end=System.currentTimeMillis();

System.out.println("花费时间："+(end-begin));

}

结果截图：

2.2. 配置mybais的二级缓存

1) 修改配置文件mapper.xml

加上，

2) 修改配置文件applicationContext.xml，开启mybatis缓存,在

"configurationProperties">

"cacheEnabled">true

"lazyLoadingEnabled">false

"aggressiveLazyLoading">true

"multipleResultSetsEnabled">true

"useColumnLabel">true

"useGeneratedKeys">true

"autoMappingBehavior">FULL

"defaultExecutorType">BATCH

"defaultStatementTimeout">25000

3) 添加配置文件spring-redis.xml

"poolConfig" class="redis.clients.jedis.JedisPoolConfig">

"maxIdle" value="2000" />

"maxTotal" value="20000" />

"minEvictableIdleTimeMillis" value="300000">

"numTestsPerEvictionRun" value="3">

"timeBetweenEvictionRunsMillis" value="60000">

"maxWaitMillis" value="20000" />

"testOnBorrow" value="false" />

"jedisConnectionFactory" class="org.springframework.data.redis.connection.jedis.JedisConnectionFactory">

"hostName" value="192.168.115.164" />

"port" value="6379" />

"poolConfig" ref="poolConfig" />

"redisCache" class="com.aaa.util.RedisCacheTransfer">

"jedisConnectionFactory" ref="jedisConnectionFactory">

4) 创建mybatis cache接口的实现类RedisCache

/**

* @author sunshaoshan

* @description 使用第三方缓存服务器，处理二级缓存

* @company AAA软件

* 2017-6-29下午2:16:56

public class RedisCache implements Cache {

private static JedisConnectionFactory jedisConnectionFactory;

private final String id;

private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

public RedisCache(final String id){

if (id == null) {

throw new IllegalArgumentException("cache instances require an ID");

}

this.id = id;

}

/**

* @description: 清空redis缓存

* @author

* @param

* @return

@Override

public void clear() {

RedisConnection connection = null;

try {

connection = jedisConnectionFactory.getConnection();

connection.flushDb();//清空redis中的数据

connection.flushAll();//#移除所有key从所有库中

} catch (Exception e) {

e.printStackTrace();

}finally{

if (connection != null) {

connection.close();

}

@Override

public String getId() {

return this.id;

}

/**

* @description: 根据key获取redis缓存中的值

* @author

* @param

* @return

@Override

public Object getObject(Object key) {

System.out.println("--------------------------------key:["+key+"]");

Object result = null;

RedisConnection connection = null;

try {

connection = jedisConnectionFactory.getConnection();

RedisSerializer serializer = new JdkSerializationRedisSerializer();

//serializer.serialize(key)将key序列化

//connection.get(serializer.serialize(key))根据key去redis中获取value

//serializer.deserialize将value反序列化

result = serializer.deserialize(connection.get(serializer.serialize(key)));

} catch (Exception e) {

e.printStackTrace();

}finally{

if (connection != null) {

connection.close();

}

return result;

}

@Override

public ReadWriteLock getReadWriteLock() {

return this.readWriteLock;

}

@Override

public int getSize() {

int result = 0;

RedisConnection connection = null;

try {

connection = jedisConnectionFactory.getConnection();

result = Integer.valueOf(connection.dbSize().toString());

} catch (Exception e) {

e.printStackTrace();

}finally{

if (connection != null) {

connection.close();

}

return result;

}

/**

* @description: 将数据保存到redis缓存

* @author

* @param

* @return

@Override

public void putObject(Object key, Object value) {

System.out.println(">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>key:"+key);

RedisConnection connection = null;

try {

connection = jedisConnectionFactory.getConnection();

RedisSerializer serializer = new JdkSerializationRedisSerializer();

System.out.println("**"+serializer.serialize(key));

//serializer.serialize(value)将value序列化，serializer.serialize(key)将key序列化

connection.set(serializer.serialize(key), serializer.serialize(value));

} catch (Exception e) {

e.printStackTrace();

}finally{

if (connection != null) {

connection.close();

}

/**

* @description: 根据key清除redis缓存中对应的值

* @author

* @param

* @return

@Override

public Object removeObject(Object key) {

RedisConnection connection = null;

Object result = null;

try {

connection = jedisConnectionFactory.getConnection();

RedisSerializer serializer = new JdkSerializationRedisSerializer();

result = connection.expireAt(serializer.serialize(key), 0);

} catch (Exception e) {

e.printStackTrace();

}finally{

if (connection != null) {

connection.close();

}

return result;

}

public static void setJedisConnectionFactory(JedisConnectionFactory jedisConnectionFactory) {

RedisCache.jedisConnectionFactory = jedisConnectionFactory;

}

5) 创建中间类，解决RedisCache.jedisConnectionFactory的静态注入，从而使MyBatis实现第三方缓存

/**

* @author sunshaoshan

* @description 创建中间类RedisCacheTransfer，完成RedisCache.jedisConnectionFactory的静态注入

* @company AAA软件

* 2018-1-12上午8:46:18

public class RedisCacheTransfer {

public void setJedisConnectionFactory(JedisConnectionFactory jedisConnectionFactory) {

RedisCache.setJedisConnectionFactory(jedisConnectionFactory);

}

6) 测试类

/**

* 使用缓存的查询时间

public static void main(String[] args) {

ApplicationContext ac =new ClassPathXmlApplicationContext("applicationContext.xml","spring-redis.xml");

EmpMapper empMapper=(EmpMapper) ac.getBean("empMapper");

Long begin=System.currentTimeMillis();

List empList = empMapper.findAllEmp();

System.out.println("员工数："+empList.size());

Long end=System.currentTimeMillis();

System.out.println("花费时间："+(end-begin));

}

7) 测试效果

第一次查询 redis服务器没有缓存,所以所耗时间较长

第二次查询

三:redis(集群版)实现mybatis的二级缓存

3.1. 修改配置文件spring-redis.xml

"redisClusterConfiguration" class="org.springframework.data.redis.connection.RedisClusterConfiguration">

"maxRedirects" value="3">

"clusterNodes">

"org.springframework.data.redis.connection.RedisClusterNode">