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MyBatis Plus整合Redis實(shí)現(xiàn)分布式二級緩存的問題

更新時(shí)間：2023年11月15日 09:43:09 作者：愛碼猿

Mybatis內(nèi)置的二級緩存在分布式環(huán)境下存在分布式問題,無法使用,但是我們可以整合Redis來實(shí)現(xiàn)分布式的二級緩存,這篇文章給大家介紹MyBatis Plus整合Redis實(shí)現(xiàn)分布式二級緩存,感興趣的朋友跟隨小編一起看看吧

MyBatis緩存描述

MyBatis提供了兩種級別的緩存，分別時(shí)一級緩存和二級緩存。一級緩存是SqlSession級別的緩存，只在SqlSession對象內(nèi)部存儲緩存數(shù)據(jù)，如果SqlSession對象不一樣就無法命中緩存，二級緩存是mapper級別的緩存，只要使用的Mapper類一樣就能夠共享緩存。

在查詢數(shù)據(jù)時(shí)，Mybatis會優(yōu)先查詢二級緩存，如果二級緩存沒有則查詢一級緩存，都沒有才會進(jìn)行數(shù)據(jù)庫查詢。

Mybatis的一級緩存默認(rèn)是開啟的，而二級緩存需要在mapper.xml配置文件內(nèi)或通過@CacheNamespace注解手動開啟。

需要注意的是，在于Spring進(jìn)行整合時(shí)，必須開啟事務(wù)一級緩存會生效，因?yàn)椴婚_啟緩存的話每次查詢都會重新創(chuàng)建一個SqlSession對象，因此無法共享緩存。

通過@CacheNamespace開啟某個Mapper的二級緩存。

@Mapper
@CacheNamespace 
public interface EmployeeMapper extends BaseMapper<Employee> {
}

開啟所有的二級緩存：

mybatis-plus:
    mapper-locations: classpath:mybatis/mapper/*.xml
    configuration:
      cache-enabled: true

MybatisPlus整合Redis實(shí)現(xiàn)分布式二級緩存

Mybatis內(nèi)置的二級緩存在分布式環(huán)境下存在分布式問題，無法使用，但是我們可以整合Redis來實(shí)現(xiàn)分布式的二級緩存。

1.引入依賴

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.5.4.1</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-redis</artifactId>
</dependency>
<dependency>
    <groupId>org.redisson</groupId>
    <artifactId>redisson-spring-boot-starter</artifactId>
    <version>3.24.3</version>
</dependency>
<dependency>
    <groupId>cn.hutool</groupId>
    <artifactId>hutool-all</artifactId>
    <version>5.8.22</version>
</dependency>

2.配置RedisTemplate

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.jsontype.impl.LaissezFaireSubTypeValidator;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.cache.CacheManager;
import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.data.redis.cache.RedisCacheConfiguration;
import org.springframework.data.redis.cache.RedisCacheManager;
import org.springframework.data.redis.cache.RedisCacheWriter;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.GenericJackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializationContext;
import org.springframework.data.redis.serializer.RedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
import java.time.Duration;
@Configuration
@EnableCaching
public class RedisConfiguration {
    private static final StringRedisSerializer STRING_SERIALIZER = new StringRedisSerializer();
    private static final GenericJackson2JsonRedisSerializer JACKSON__SERIALIZER = new GenericJackson2JsonRedisSerializer();
    @Bean
    @Primary
    public CacheManager redisCacheManager(RedisConnectionFactory redisConnectionFactory) {
        //設(shè)置緩存過期時(shí)間
        RedisCacheConfiguration redisCacheCfg = RedisCacheConfiguration.defaultCacheConfig()
                .entryTtl(Duration.ofHours(1))
                .serializeKeysWith(RedisSerializationContext.SerializationPair.fromSerializer(STRING_SERIALIZER))
                .serializeValuesWith(RedisSerializationContext.SerializationPair.fromSerializer(JACKSON__SERIALIZER));
        return RedisCacheManager.builder(RedisCacheWriter.nonLockingRedisCacheWriter(redisConnectionFactory))
                .cacheDefaults(redisCacheCfg)
                .build();
    }
    @Bean
    @Primary
    @ConditionalOnMissingBean(name = "redisTemplate")
    public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory factory) {
        // 配置redisTemplate
        RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
        redisTemplate.setConnectionFactory(factory);
        // key序列化
        redisTemplate.setKeySerializer(STRING_SERIALIZER);
        // value序列化
        redisTemplate.setValueSerializer(JACKSON__SERIALIZER);
        // Hash key序列化
        redisTemplate.setHashKeySerializer(STRING_SERIALIZER);
        // Hash value序列化
        redisTemplate.setHashValueSerializer(JACKSON__SERIALIZER);
        // 設(shè)置支持事務(wù)
        redisTemplate.setEnableTransactionSupport(true);
        redisTemplate.afterPropertiesSet();
        return redisTemplate;
    }
    @Bean
    public RedisSerializer<Object> redisSerializer() {
        //創(chuàng)建JSON序列化器
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
        //必須設(shè)置，否則無法將JSON轉(zhuǎn)化為對象，會轉(zhuǎn)化成Map類型
        objectMapper.activateDefaultTyping(LaissezFaireSubTypeValidator.instance, ObjectMapper.DefaultTyping.NON_FINAL);
        return new GenericJackson2JsonRedisSerializer(objectMapper);
    }
}

3.自定義緩存類

import cn.hutool.extra.spring.SpringUtil;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.apache.ibatis.cache.Cache;
import org.redisson.api.RReadWriteLock;
import org.redisson.api.RedissonClient;
import org.springframework.data.redis.connection.RedisServerCommands;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReadWriteLock;
@Slf4j
public class MybatisRedisCache implements Cache {
    // redisson 讀寫鎖
    private final RReadWriteLock redissonReadWriteLock;
    // redisTemplate
    private final RedisTemplate redisTemplate;
    // 緩存Id
    private final String id;
    //過期時(shí)間 10分鐘
    private final long expirationTime = 1000*60*10;
    public MybatisRedisCache(String id) {
        this.id = id;
        //獲取redisTemplate
        this.redisTemplate = SpringUtil.getBean(RedisTemplate.class);
        //創(chuàng)建讀寫鎖
        this.redissonReadWriteLock = SpringUtil.getBean(RedissonClient.class).getReadWriteLock("mybatis-cache-lock:"+this.id);
    }
    @Override
    public void putObject(Object key, Object value) {
        //使用redis的Hash類型進(jìn)行存儲
        redisTemplate.opsForValue().set(getCacheKey(key),value,expirationTime, TimeUnit.MILLISECONDS);
    }
    @Override
    public Object getObject(Object key) {
        try {
            //根據(jù)key從redis中獲取數(shù)據(jù)
            Object cacheData = redisTemplate.opsForValue().get(getCacheKey(key));
            log.debug("[Mybatis 二級緩存]查詢緩存,cacheKey={},data={}",getCacheKey(key), JSONUtil.toJsonStr(cacheData));
            return cacheData;
        } catch (Exception e) {
            log.error("緩存出錯",e);
        }
        return null;
    }
    @Override
    public Object removeObject(Object key) {
        if (key != null) {
            log.debug("[Mybatis 二級緩存]刪除緩存,cacheKey={}",getCacheKey(key));
            redisTemplate.delete(key.toString());
        }
        return null;
    }
    @Override
    public void clear() {
        log.debug("[Mybatis 二級緩存]清空緩存,id={}",getCachePrefix());
        Set keys = redisTemplate.keys(getCachePrefix()+":*");
        redisTemplate.delete(keys);
    }
    @Override
    public int getSize() {
        Long size = (Long) redisTemplate.execute((RedisCallback<Long>) RedisServerCommands::dbSize);
        return size.intValue();
    }
    @Override
    public ReadWriteLock getReadWriteLock() {
        return this.redissonReadWriteLock;
    }
    @Override
    public String getId() {
        return this.id;
    }
    public String getCachePrefix(){
        return "mybatis-cache:%s".formatted(this.id);
    }
    private String getCacheKey(Object key){
        return getCachePrefix()+":"+key;
    }
}

4.Mapper接口上開啟二級緩存

//開啟二級緩存并指定緩存類
@CacheNamespace(implementation = MybatisRedisCache.class,eviction = MybatisRedisCache.class)
@Mapper
public interface EmployeeMapper extends BaseMapper<Employee> {
}

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