浅析SpringBoot整合Mybatis如何实现二级缓存

mybatis 原生

二级缓存，是指多个Sqlsession之间共享数据，但是也可以使用Redis这样的缓存作为存储点。 但是不支持mybatisplus 里的方法。

处理类，用于拦截mapper缓存。

import org.apache.ibatis.cache.Cache;
public record MybatisRedisCache(String id) implements Cache {

    private static final StringRedisTemplate redisTemplate;

    static {
        redisTemplate = SpringUtil.getBean(StringRedisTemplate.class);
    }

    @Override
    public String getId() {
        return id;
    }

    @Override
    public void putObject(Object key, Object value) {
        if (value != null) {
            redisTemplate.opsForValue().set(getKey(key), JSONUtil.toJsonStr(value));
        }
    }

    @Override
    public Object getObject(Object key) {
        String string = redisTemplate.opsForValue().get(getKey(key));
        if (string == null) return null;
        return isArray(string);
    }

    @Override
    public Object removeObject(Object key) {
        String redisKey = getKey(key);
        Object value = redisTemplate.opsForValue().get(redisKey);
        redisTemplate.delete(redisKey);
        return value;
    }

    @Override
    public void clear() {
        redisTemplate.delete(Objects.requireNonNull(redisTemplate.keys(getKey("*"))));
    }

    @Override
    public int getSize() {
        return 0;
    }

    private String getKey(Object key) {
        return id + ":" + key.hashCode();
    }

    public Object isArray(String str) {
        JSON json = JSONUtil.parse(str);
        if (json instanceof cn.hutool.json.JSONArray) {
            // 是数组
            return JSONUtil.toList((cn.hutool.json.JSONArray) json, Object.class);
        }
        if (json instanceof cn.hutool.json.JSONObject) {
            // 是对象
            return JSONUtil.toBean((cn.hutool.json.JSONObject) json, Object.class);
        }
        throw new RuntimeException("缓存数据格式错误");
    }

}

mapper xml

一定要加 cache-ref 才能进行二级缓存

<mapper namespace="com.example.dao.UserMapper">

    <cache-ref namespace="com.example.dao.UserMapper"/>

    <select id="selectAll" resultType="com.example.Demo">
        select *
        from demo
    </select>
</mapper>

配置 CacheNamespace 使用就可以了

@CacheNamespace(implementation = MybatisRedisCache.class)
public interface UserMapper extends BaseMapper<Demo> {

    List<Demo> selectAll();

}

Spring Cache

@Configuration
@EnableCaching
public class RedisCacheConfig {

    @Bean
    public CacheManager cacheManager(RedisConnectionFactory factory) {
        RedisCacheConfiguration config = RedisCacheConfiguration.defaultCacheConfig()
                .entryTtl(Duration.ofMinutes(10)) // 默认缓存 10 分钟
                .disableCachingNullValues() // 避免存入控制
                .serializeValuesWith( // 设置序列化
                        RedisSerializationContext.SerializationPair.fromSerializer(new GenericJackson2JsonRedisSerializer())
                );
        // 返回
        return RedisCacheManager.builder(factory).cacheDefaults(config).build();
    }

}

Cacheable 缓存、CacheEvict 删除，拼接 key

@Service
public class DemoService extends ServiceImpl<UserMapper, Demo> {

    @Cacheable(value = "user:cache", key = "#id")
    public Demo getOne(Long id) {
        return getById(id);
    }


    @Caching(evict = {
            @CacheEvict(value = "user:cache", key = "#id"),
            @CacheEvict(value = "user:all", allEntries = true)}
    )
    public void deleteById(String id) {
        removeById(id);
    }

    // 更新数据后刷新缓存
    @Caching(
            put = {@CachePut(value = "user:cache", key = "#demo.id", unless = "#result == null")},
            evict = {@CacheEvict(value = "user:all", allEntries = true)}
    )
    public void updateUser(Demo demo) {
        updateById(demo);
    }

    @Cacheable(value = "user:all")
    public List<Demo> listDemo() {
        return list();
    }

}

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