Mybatis-Redis二级缓存分布式实现
Mybatis二级缓存默认采用的org.apache.ibatis.cache.impl.PerpetualCache实现的（基于内存中Map
Mybatis支持Ehcache二级缓存配置，默认适用于单实例部署，亦可以支持分布式部署（配置较为复杂，维护困难，支持RMI（手动、自动 - 组播 ）、JGroups、EhCache Server等部署方式）；
关于Ehcache分布式部署可参见：
https://blog.csdn.net/tang06211015/article/details/52281551
http://blog.sina.com.cn/s/blog_6151984a0101816j.html
Ehcache & Redis对比：
（1）Ehcache（分布式缓存）直接在jvm虚拟机中缓存，速度快，效率高；但是缓存共享麻烦，集群分布式应用不方便。
（2）Redis（集中式缓存）是通过socket访问到缓存服务，效率比ecache低，比数据库要快很多，处理集群和分布式缓存方便，有成熟的方案。
因此考虑使用Redis支持分布式缓存，Mybatis官方提供mybatis-redis插件（http://www.mybatis.org/redis-cache/），官方插件需要单独配置/redis.properties并且维护一个JedisConfigPool，考虑到单独配置与项目已有Redis配置重复且无法复用本地配置，因此决定参照官方org.mybatis.caches.redis.RedisCache来重写自己的MybatisRedisCache 。
MybatisRedisCache实现如下：
import com.fasterxml.jackson.annotation.JsonAutoDetect; import com.fasterxml.jackson.annotation.PropertyAccessor; import com.fasterxml.jackson.databind.ObjectMapper; import org.apache.ibatis.cache.Cache; import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; import org.springframework.data.redis.core.RedisTemplate; import java.util.concurrent.locks.ReadWriteLock; import java.util.concurrent.locks.ReentrantReadWriteLock; /** * Mybatis - redis二级缓存 * * @author luohq * @date 2019/3/15 */ public final class MybatisRedisCache implements Cache { /** * 日志工具类 */ private static final Logger logger = LogManager.getLogger(MybatisRedisCache.class); /** * 读写锁 */ private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock(); /** * ID */ private String id; /** * 集成redisTemplate */ private static RedisTemplate redisTemplate; /** * Jackson-databind对象序列化器（核心） */ private static ObjectMapper objectMapper; /** * 序列化器初始化 */ static { objectMapper = new ObjectMapper(); //所有属性均可序列化 objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY); /** * 序列化类型信息（使用objectMapper.readValue(hashVal, Object.class)也可以实现相应类型的序列化和反序列化 * 好处：只定义一个序列化器就可以了（通用）） */ objectMapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL); } public MybatisRedisCache() { } public MybatisRedisCache(String id) { if (id == null) { throw new IllegalArgumentException("Cache instances require an ID"); } else { logger.info("MybatisRedisCache.id={}", id); this.id = id; } } @Override public String getId() { return this.id; } @Override public int getSize() { try { Long size = redisTemplate.opsForHash().size(this.id.toString()); logger.info("MybatisRedisCache.getSize: {}->{}", id, size); return size.intValue(); } catch (Exception e) { e.printStackTrace(); } return 0; } @Override public void putObject(final Object key, final Object value) { try { String hashVal = objectMapper.writeValueAsString(value); logger.info("MybatisRedisCache.putObject: {}->{}->{}", id, key, hashVal); redisTemplate.opsForHash().put(this.id.toString(), key.toString(), hashVal); } catch (Exception e) { e.printStackTrace(); } } @Override public Object getObject(final Object key) { try { String hashVal = (String) redisTemplate.opsForHash().get(this.id.toString(), key.toString()); logger.info("MybatisRedisCache.getObject: {}->{}->{}", id, key, hashVal); if (null == hashVal) { return null; } return objectMapper.readValue(hashVal, Object.class); } catch (Exception e) { e.printStackTrace(); return null; } } @Override public Object removeObject(final Object key) { try { redisTemplate.opsForHash().delete(this.id.toString(), key.toString()); logger.info("MybatisRedisCache.removeObject: {}->{}->{}", id, key); } catch (Exception e) { e.printStackTrace(); } return null; } @Override public void clear() { try { redisTemplate.delete(this.id.toString()); logger.info("MybatisRedisCache.clear: {}", id); } catch (Exception e) { e.printStackTrace(); } } @Override public ReadWriteLock getReadWriteLock() { return this.readWriteLock; } @Override public String toString() { return "MybatisRedisCache {" + this.id + "}"; } /** * 设置redisTemplate * * @param redisTemplate */ public void setRedisTemplate(RedisTemplate redisTemplate) { MybatisRedisCache.redisTemplate = redisTemplate; } }
MybatisRedisCache改进版：
改进如下：
（1）将序列化器直接配置进redisTemplate中，由redisTemplate来负责序列化；
代码如下：
import com.xxx.util.JsonUtils; import org.apache.ibatis.cache.Cache; import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; import org.springframework.data.redis.core.RedisTemplate; import java.util.concurrent.locks.ReadWriteLock; import java.util.concurrent.locks.ReentrantReadWriteLock; /** * Mybatis - redis二级缓存 * * @author luohq * @date 2019/3/15 */ public final class MybatisRedisCache implements Cache { /** * 日志工具类 */ private static final Logger logger = LogManager.getLogger(MybatisRedisCache.class); /** * 读写锁 */ private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock(); /** * ID */ private String id; /** * 集成redisTemplate */ private static RedisTemplate redisTemplate; public MybatisRedisCache() { } public MybatisRedisCache(String id) { if (id == null) { throw new IllegalArgumentException("Cache instances require an ID"); } else { logger.debug("MybatisRedisCache.id={}", id); this.id = id; } } @Override public String getId() { return this.id; } @Override public int getSize() { try { Long size = redisTemplate.opsForHash().size(this.id.toString()); logger.debug("MybatisRedisCache.getSize: {}->{}", id, size); return size.intValue(); } catch (Exception e) { e.printStackTrace(); } return 0; } @Override public void putObject(final Object key, final Object value) { try { logger.debug("MybatisRedisCache.putObject: {}->{}->{}", id, key, JsonUtils.toJson(value)); redisTemplate.opsForHash().put(this.id.toString(), key.toString(), value); } catch (Exception e) { e.printStackTrace(); } } @Override public Object getObject(final Object key) { try { Object hashVal = redisTemplate.opsForHash().get(this.id.toString(), key.toString()); logger.debug("MybatisRedisCache.getObject: {}->{}->{}", id, key, JsonUtils.toJson(hashVal)); return hashVal; } catch (Exception e) { e.printStackTrace(); return null; } } @Override public Object removeObject(final Object key) { try { redisTemplate.opsForHash().delete(this.id.toString(), key.toString()); logger.debug("MybatisRedisCache.removeObject: {}->{}->{}", id, key); } catch (Exception e) { e.printStackTrace(); } return null; } @Override public void clear() { try { redisTemplate.delete(this.id.toString()); logger.debug("MybatisRedisCache.clear: {}", id); } catch (Exception e) { e.printStackTrace(); } } @Override public ReadWriteLock getReadWriteLock() { return this.readWriteLock; } @Override public String toString() { return "MybatisRedisCache {" + this.id + "}"; } /** * 设置redisTemplate * * @param redisTemplate */ public void setRedisTemplate(RedisTemplate redisTemplate) { MybatisRedisCache.redisTemplate = redisTemplate; } }
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.PropertyAccessor;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.redis.connection.RedisConnectionFactory;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.serializer.Jackson2JsonRedisSerializer;
import org.springframework.data.redis.serializer.StringRedisSerializer;
/**
* Redis配置
*
* @author luohq
* @date: 2019/03/13
*/
@Configuration
public class RedisConfig {
/**
* 配置RedisTemplate
*
* @param factory
* @return
*/
@Bean
public RedisTemplate redisTemplate(RedisConnectionFactory factory, Jackson2JsonRedisSerializer redisJsonSerializer) {
RedisTemplate template = new RedisTemplate<>();
//redis连接工厂
template.setConnectionFactory(factory);
StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
//redis.key序列化器
template.setKeySerializer(stringRedisSerializer);
//redis.value序列化器
template.setValueSerializer(redisJsonSerializer);
//redis.hash.key序列化器
template.setHashKeySerializer(stringRedisSerializer);
//redis.hash.value序列化器
template.setHashValueSerializer(redisJsonSerializer);
//调用其他初始化逻辑
template.afterPropertiesSet();
//这里设置redis事务一致
template.setEnableTransactionSupport(true);
return template;
}
/**
* 配置redis Json序列化器
*
* @return
*/
@Bean
public Jackson2JsonRedisSerializer redisJsonSerializer() {
//使用Jackson2JsonRedisSerializer来序列化和反序列化redis的value值（默认使用JDK的序列化方式）
Jackson2JsonRedisSerializer serializer = new Jackson2JsonRedisSerializer(Object.class);
ObjectMapper mapper = new ObjectMapper();
mapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);
mapper.enableDefaultTyping(ObjectMapper.DefaultTyping.NON_FINAL);
serializer.setObjectMapper(mapper);
return serializer;
}
}
使用方式：
（1）开启Mybatis二级缓存设置
方式1：mybatis-config.xml
...
方式2：Springboot - application.properties
#使全局的映射器启用或禁用缓存。 mybatis.configuration.cache-enabled=true
（2）在mapper.xml使用二级缓存
......