Mybatis使用Redis二级缓存

在Mybatis中允许开发者自定义自己的缓存，本文将使用Redis作为Mybatis的二级缓存。在Mybatis中定义二级缓存，需要如下配置：

1、 MyBatis支持二级缓存的总开关：全局配置变量参数“cacheEnabled=true”

2、select语句所在的Mapper需配置了<cache> 或<cached-ref>节点

3、select语句的参数 useCache=true

Mybatis配置文件如下：

<settings>

	<!-- 这个配置使全局的映射器启用或禁用缓存 -->

   	<setting name="cacheEnabled" value="true" />

   	<!-- 对于未知的SQL查询，允许返回不同的结果集以达到通用的效果 -->

  	<setting name="multipleResultSetsEnabled" value="true"/>

    	<!-- 配置默认的执行器。SIMPLE 执行器没有什么特别之处。REUSE 执行器重用预处理语句。BATCH 执行器重用语句和批量更新 -->

    	<setting name="defaultExecutorType" value="REUSE" />

    	<!-- 全局启用或禁用延迟加载。当禁用时，所有关联对象都会即时加载。 -->

    	<setting name="lazyLoadingEnabled" value="false" />

    	<setting name="aggressiveLazyLoading" value="true" />

   	<!-- <setting name="enhancementEnabled" value="true"/> -->

    	<!-- 设置超时时间，它决定驱动等待一个数据库响应的时间。 -->

    	<setting name="defaultStatementTimeout" value="25000" />

</settings>

　Mybatis的Mapper的配置文件如下：

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

	"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="user">

	<!-- 二级缓存 -->

	<cache type="com.qunar.mobile.mybatis.cache.QRedisCache"/>

	<select id="getUsers" resultType="User" useCache="true">

		select

			user_id as userId, user_name as username, user_desc as userDesc, create_time as createTime

		from bisystem_user

	</select>

</mapper>

　　自定义二级缓存需要实现Mybatis的Cache接口，Redis缓存实现如下：

public class QRedisCache implements Cache {

	private String cacheId;

	private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock(true); 

	public QRedisCache(String cacheId) {

		if (cacheId == null) {

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

		}

		this.cacheId = cacheId;

	}

	@Override

	public String getId() {

		return cacheId;

	}

	@Override

	public void putObject(Object key, Object value) {

		JedisUtils.put(key, value);

	}

	@Override

	public Object getObject(Object key) {

		return JedisUtils.get(key);

	}

	@Override

	public Object removeObject(Object key) {

		return JedisUtils.remove(key);

	}

	@Override

	public void clear() {

		JedisUtils.removeAll();

	}

	@Override

	public int getSize() {

		return 0;

	}

	@Override

	public ReadWriteLock getReadWriteLock() {

		return readWriteLock;

	}

}

　　在QRedisCache使用的辅助类JedisUtils及SerializeUtils实现如下：

public class JedisUtils {

	private static final Logger logger = Logger.getLogger(JedisUtils.class);

	private static JedisPool JEDISPOOL;

	static {

		Properties props = new Properties();

		try {

			props.load(JedisUtils.class.getResourceAsStream("/redis.properties"));

			JedisPoolConfig conf = new JedisPoolConfig();

			conf.setMaxIdle(Integer.valueOf(props.getProperty("jedis.pool.maxIdle")));

			conf.setTestOnBorrow(Boolean.valueOf(props.getProperty("jedis.pool.testOnBorrow")));

			conf.setTestOnReturn(Boolean.valueOf(props.getProperty("jedis.pool.testOnReturn")));

			JEDISPOOL = new JedisPool(conf, props.getProperty("redis.ip"), Integer.valueOf(props.getProperty("redis.port")));

		} catch (IOException e) {

			logger.error("加载[jedis.properties]异常[" + e.getMessage() + "]", e);

		}

	}

	public static Jedis getJedis() {

		return JEDISPOOL.getResource();

	}

	public static void recycleJedis(Jedis jedis) {

		jedis.close();

	}

	/**

	 * Redis存储Object序列化流

	 * */

	public static void put(Object key, Object value) {

		Jedis jedis = getJedis();

		jedis.set(SerializeUtils.serialize(key), SerializeUtils.serialize(value));

		recycleJedis(jedis);

	}

	public static <T> T get(Object key) {

		Jedis jedis = getJedis();

		T value = SerializeUtils.unserialize(jedis.get(SerializeUtils.serialize(key)));

		recycleJedis(jedis);

		return value;

	}

	public static Long remove(Object key) {

		Jedis jedis = getJedis();

		Long num = jedis.del(SerializeUtils.serialize(key));

		recycleJedis(jedis);

		return num;

	}

	public static void removeAll() {

		Jedis jedis = getJedis();

		jedis.flushDB();

		recycleJedis(jedis);

	}

}

public class SerializeUtils {

	private static final Logger logger = Logger.getLogger(SerializeUtils.class);

	private static void close(ObjectOutputStream objectOutputStream, ByteArrayOutputStream byteArrayOutputStream) {

		try {

			if (byteArrayOutputStream != null) {

				byteArrayOutputStream.close();

			}

			if (objectOutputStream != null) {

				objectOutputStream.close();

			}

		} catch (Exception e) {

			e.printStackTrace();

			logger.error("关闭IO资源异常[" + e.getMessage() + "]", e);

		}

	}

	private static void close(ObjectInputStream objectInputStream, ByteArrayInputStream byteArrayInputStream) {

		try {

			if (objectInputStream != null) {

				objectInputStream.close();

			}

			if (byteArrayInputStream != null) {

				byteArrayInputStream.close();

			}

		} catch (Exception e) {

			e.printStackTrace();

			logger.error("关闭IO资源异常[" + e.getMessage() + "]", e);

		}

	}

	public static byte[] serialize(Object object) {

		ObjectOutputStream objectOutputStream = null;

		ByteArrayOutputStream byteArrayOutputStream = null;

		try {

			byteArrayOutputStream = new ByteArrayOutputStream();

			objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);

			objectOutputStream.writeObject(object);

			byte[] bytes = byteArrayOutputStream.toByteArray();

			return bytes;

		} catch (Exception e) {

			e.printStackTrace();

			logger.error("序列化对象异常[" + e.getMessage() + "]", e);

		} finally {

			close(objectOutputStream, byteArrayOutputStream);

		}

		return null;

	}

	@SuppressWarnings("unchecked")

	public static <T> T unserialize(byte[] bytes) {

		if (bytes == null)

			return null;

		ByteArrayInputStream byteArrayInputStream = null;

		ObjectInputStream objectInputStream = null;

		try {

			byteArrayInputStream = new ByteArrayInputStream(bytes);

			objectInputStream = new ObjectInputStream(byteArrayInputStream);

			return (T) objectInputStream.readObject();

		} catch (Exception e) {

			e.printStackTrace();

		} finally {

			close(objectInputStream, byteArrayInputStream);

		}

		return null;

	}

}

　　Redis的配置文件redis.properties如下：

#redis服务器ip#   

redis.ip=192.168.2.107

#redis服务器端口号#  

redis.port=6379

#********jedis池参数设置********#  

#jedis的最大分配对象#  

jedis.pool.maxActive=3000

#jedis最大保存idel状态对象数 #  

jedis.pool.maxIdle=1000

#jedis池没有对象返回时，最大等待时间 #  

jedis.pool.maxWait=1500

#jedis调用borrowObject方法时，是否进行有效检查#  

jedis.pool.testOnBorrow=true

#jedis调用returnObject方法时，是否进行有效检查 #  

jedis.pool.testOnReturn=true

巴特西

Mybatis使用Redis二级缓存

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