Spring中使用Redis做为Mybatis二级缓存

Mybatis缓存通过org.apache.ibatis.cache.Cache实现，利用Redis做Mybatis的二级缓存需要实现这个接口。

缓存过程中产生的key注意存储，flushCache的时候要删除这些key对应的缓存值。这里把这些key保存到为redis的list结构，以id作为list的key，每个mapper产生的id不变。

• 使用redisTemplate操作redis，可以参考文档：Spring集成shiro使用redis管理session
• 不需要专门为保存key建立一个redis.list，直接使用redisTemplate.keys(key+"*")就可以，同样参考文档：Spring集成shiro使用redis管理session

MybatisRedisCache.java

package com.sdhs.mob.common.redis;

import org.apache.ibatis.cache.Cache;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.springframework.data.redis.connection.RedisConnection;
import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;
import org.springframework.data.redis.serializer.JdkSerializationRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializer;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * mybatis redis 二级缓存
 *
 * @author seer
 * @date 2018/3/13 14:17
 */
public class MybatisRedisCache implements Cache {
    private static Logger LOGGER = LogManager.getLogger(MybatisRedisCache.class);
    private final String id;
    private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

    private static JedisConnectionFactory jedisConnectionFactory;

    /**
     * 这个地方需要静态注入，这里通过中间类 MybatisRedisCacheTransfer 实现的
     * @param jedisConnectionFactory
     */
    public static void setJedisConnectionFactory(JedisConnectionFactory jedisConnectionFactory) {
        MybatisRedisCache.jedisConnectionFactory = jedisConnectionFactory;
    }

    public MybatisRedisCache(final String id) {
        if (null == id || "".equals(id)) {
            throw new IllegalArgumentException("mybatis redis cache need an id.");
        }
        this.id = id;
        LOGGER.debug("mybatis redis cache id: {}", id);
    }


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

    /**
     * 存值
     * @param key
     * @param value
     */
    @Override
    public void putObject(Object key, Object value) {
        if (null == key) {
            return;
        }
        LOGGER.debug("mybatis redis cache put. K={} value={}", key, value);
        RedisConnection redisConnection = null;
        try {
            redisConnection = jedisConnectionFactory.getConnection();
            RedisSerializer serializer = new JdkSerializationRedisSerializer();
            redisConnection.set(serializer.serialize(key), serializer.serialize(value));

            // 将key保存到redis.list中
            redisConnection.lPush(serializer.serialize(id), serializer.serialize(key));
        } catch (Exception e) {
            LOGGER.error("mybatis redis cache put exception. K=" + key + " V=" + value + "", e);
        } finally {
            if (null != redisConnection) {
                redisConnection.close();
            }
        }
    }

    /**
     * 取值
     * @param key
     * @return
     */
    @Override
    public Object getObject(Object key) {
        if (null == key) {
            return null;
        }
        LOGGER.debug("mybatis redis cache get. K={}", key);
        RedisConnection redisConnection = null;
        Object result = null;
        try {
            redisConnection = jedisConnectionFactory.getConnection();
            RedisSerializer serializer = new JdkSerializationRedisSerializer();
            result = serializer.deserialize(redisConnection.get(serializer.serialize(key)));
        } catch (Exception e) {
            LOGGER.error("mybatis redis cache get exception. K=" + key + " V=" + result + "", e);
        } finally {
            if (null != redisConnection) {
                redisConnection.close();
            }
        }
        return result;
    }

    /**
     * 删值
     * @param key
     * @return
     */
    @Override
    public Object removeObject(Object key) {
        if (null == key) {
            return null;
        }
        LOGGER.debug("mybatis redis cache remove. K={}", key);
        RedisConnection redisConnection = null;
        Object result = null;
        try {
            redisConnection = jedisConnectionFactory.getConnection();
            RedisSerializer serializer = new JdkSerializationRedisSerializer();
            // 讲key设置为立即过期
            result = redisConnection.expireAt(serializer.serialize(key), 0);
            
            // 将key从redis.list中删除
            redisConnection.lRem(serializer.serialize(id), 0, serializer.serialize(key));
        } catch (Exception e) {
            LOGGER.error("mybatis redis cache remove exception. " + key + " V=" + result + "", e);
        } finally {
            if (null != redisConnection) {
                redisConnection.close();
            }
        }
        return result;
    }

    /**
     * 清空缓存
     * flushCache="true" 的时候会调用这个地方
     */
    @Override
    public void clear() {
        LOGGER.debug("mybatis redis cache clear. ");
        RedisConnection redisConnection = null;
        try {
            redisConnection = jedisConnectionFactory.getConnection();

            /**
             * 千万不要直接 redisConnection.flushDb()，会把整个redis的东西都清除掉，我不相信你的redis里没有其他东西
             * 获取redis.list中的保存的key值，遍历删除
             */
            Long length = redisConnection.lLen(serializer.serialize(id));
            if (0 == length) {
                return;
            }
            List<byte[]> keyList = redisConnection.lRange(serializer.serialize(id), 0, length - 1);
            for (byte[] key : keyList) {
                redisConnection.expireAt(key, 0);
            }
            redisConnection.expireAt(serializer.serialize(id), 0);
            keyList.clear();
        } catch (Exception e) {
            LOGGER.error("mybatis redis cache clear exception. ", e);
        } finally {
            if (null != redisConnection) {
                redisConnection.close();
            }
        }
    }

    @Override
    public int getSize() {
        int result = 0;
        try {
            RedisConnection redisConnection = jedisConnectionFactory.getConnection();
            result = Math.toIntExact(redisConnection.dbSize());
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }

    @Override
    public ReadWriteLock getReadWriteLock() {
        return this.readWriteLock;
    }
}

类中采用了JdkSerializationRedisSerializer序列化Redis的key，几种序列化方式比较可以参照：关于Spring Data redis几种对象序列化的比较

clear()的时候千万不要直接 redisConnection.flushDb()，会把整个redis的东西都清除掉。

---

MybatisRedisCacheTransfer.java

package com.sdhs.mob.common.redis;

import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;

/**
 * mybatis redis 二级缓存参数传递
 *
 * @author seer
 * @date 2018/3/13 14:17
 */
public class MybatisRedisCacheTransfer {
    public void setJedisConnectionFactory(JedisConnectionFactory jedisConnectionFactory) {
        MybatisRedisCache.setJedisConnectionFactory(jedisConnectionFactory);
    }
}

<bean class="com.sdhs.mob.common.redis.MybatisRedisCacheTransfer">
    <property name="jedisConnectionFactory" ref="jedisConnectionFactory"/>
</bean>

对MybatisRedisCache.java中的jedisConnectionFactory注入传递

---

Mybatis的配置和使用

mybatis-config.xml

<configuration>
    <settings>
    <!-- 启动二级缓存 -->
        <setting name="cacheEnabled" value="true" />
    </settings>
</configuration>

在mapper.xml中使用

<mapper namespace="com.sdhs.mapper.AddressMapper">
    <!-- 配置缓存类 -->
    <cache type="com.sdhs.mob.common.redis.MybatisRedisCache"/>
    <resultMap id="baseResultMap" type="xxx">
    </resultMap>

    <!--
      flushCache="true"
      insert、delete、update的时候清空缓存
    -->
    <insert id="save"
            parameterType="xxx"
            useGeneratedKeys="true"
            flushCache="true"
            keyProperty="addrId">
        INSERT INTO Address
        <set>
            <include refid="setSql"/>
        </set>
    </insert>

    <!--
      useCache="true"
      select的时候使用缓存
    -->
    <select id="list"
            parameterType="xxx"
            resultMap="baseResultMap"
            useCache="true">
        SELECT
        <include refid="colSql"/>
        FROM es_address
        <where>
            <include refid="whereSql"/>
        </where>
        ORDER BY modifyDate desc
        <include refid="limitSql"/>
    </select>
<mapper>

Test的时候可以观察下两次相同查询时日志打印，查询和修改时Redis里key的变化。

参考文档：spring+springmvc+mybatis+redis实现缓存 - 甘雨路 - 博客园 感谢作者