Mybatis采用redis实现二级缓存

Mybatis的缓存，可以分为一级缓存与二级缓存。一级缓存以一次sqlSession为单位，保存查找的信息。每次有更新操作的时候，例如删除，添加，修改等这些操作，缓存区都会刷新。二级缓存以一个或者多个namespace为单位，保存信息。一个简述，不再细讲。
Mybatis提供了一个Cache接口，在我们要实现自己的缓存机制时，需要自己去实现这个接口。

Cache接口与方法：

下面是源码，方法都是见名析义的，自个加了些注释。

public interface Cache {

/**
* @return The identifier of this cache
*/
String getId();//返回ID，顾名思义，在自己实现接口时，也要定义一个ID属性，并且返回。

/**
* @param key Can be any object but usually it is a {@link CacheKey}
* @param value The result of a select.
*/
/**
设置key-value，就是通过键值对的方式缓存数据，mybatis的一级缓存也是通过Map这样实现的。
*/
void putObject(Object key, Object value);

/**
* @param key The key
* @return The object stored in the cache.
*/
/**
根据key查找value
*/
Object getObject(Object key);

/**
* As of 3.3.0 this method is only called during a rollback
* for any previous value that was missing in the cache.
* This lets any blocking cache to release the lock that
* may have previously put on the key.
* A blocking cache puts a lock when a value is null
* and releases it when the value is back again.
* This way other threads will wait for the value to be
* available instead of hitting the database.
*
*
* @param key The key
* @return Not used
*/
/**
按照key移除value
*/
Object removeObject(Object key);

/**
* Clears this cache instance
* 清除整个缓存空间。
*/
void clear();

/**
* Optional. This method is not called by the core.
* 返回缓存的数目
* @return The number of elements stored in the cache (not its capacity).
*/
int getSize();

/**
* Optional. As of 3.2.6 this method is no longer called by the core.
*
* Any locking needed by the cache must be provided internally by the cache provider.
* 可重入读写锁制
* @return A ReadWriteLock
*/
ReadWriteLock getReadWriteLock();

}

基本是这样子，其中，有几个方法一定要有具体的实现。分别是
储值，取值，按key移除，整个清空四个方法。另外，还要实现一个带有ID参数的构造器，否则会抛异常。
怎么使用jedis，网上有很多，就不再说了。自己写的代码如下：

import org.apache.ibatis.cache.Cache;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.data.redis.connection.jedis.JedisConnection;
import org.springframework.data.redis.connection.jedis.JedisConnectionFactory;
import org.springframework.data.redis.serializer.JdkSerializationRedisSerializer;
import org.springframework.data.redis.serializer.RedisSerializer;
import redis.clients.jedis.exceptions.JedisConnectionException;

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

/**
* 测试，Mybatis采用Redis作为二级缓存
*/
public class RedisCacheTest implements Cache {

/**
 * logger
 */
private static Logger logger = LoggerFactory.getLogger(RedisCacheTest.class);   
private String id;
private final ReadWriteLock readWriteLock = new ReentrantReadWriteLock();
private static JedisConnectionFactory jedisConnectionFactory;
private static String expire;

public RedisCacheTest() {}
public RedisCacheTest(String id) {
    if (id == null) {
        throw new IllegalArgumentException("Cache instances require an ID");
    }
    this.id = id;
}

public String getId() {
    return id;
}

public void putObject(Object key, Object value) {
    JedisConnection jedisConnection = null;
    jedisConnectionFactory.afterPropertiesSet();
    try {
        jedisConnection = jedisConnectionFactory.getConnection();
        RedisSerializer