Mybatis学习第15节 -- 二级缓存

二级缓存默认不开启, 开启之后, 可以在不同的session范围内执行相同的数据查询, 只进行一次数据库检索

开启设置

1. 在mapper文件中 设置cache
2. 在实体类中实现序列化接口, 否则会报错NotSerializableException

测试

@Test
public void testCacheLevelTwo() {
    SqlSession session = MyBatisUtil.getSqlSession();
    ShopMapper mapper = session.getMapper(ShopMapper.class);
    System.out.println(mapper.getShopById(1));
    session.close();

    session = MyBatisUtil.getSqlSession();
    mapper = session.getMapper(ShopMapper.class);
    System.out.println(mapper.getShopById(1));
    session.close();
}

映射文件

添加cache标签

<mapper namespace="io.github.coinsjack.dao.ShopMapper">

    <cache/>

结果

可以看到我在另一个session里面进行相同的数据查询时, 并没有再次进行实际地数据库检索

2018-12-28 19:27:06,533 [main] DEBUG [io.github.coinsjack.dao.ShopMapper] - Cache Hit Ratio [io.github.coinsjack.dao.ShopMapper]: 0.0
2018-12-28 19:27:06,960 [main] DEBUG [io.github.coinsjack.dao.ShopMapper.getShopById] - ==> Preparing: select * from tb_shop where `shop_id` = ? 
2018-12-28 19:27:07,052 [main] DEBUG [io.github.coinsjack.dao.ShopMapper.getShopById] - ==> Parameters: 1(Integer)
2018-12-28 19:27:07,143 [main] DEBUG [io.github.coinsjack.dao.ShopMapper.getShopById] - <== Total: 1
Shop{id=1, ownerId=1, areaId=3, categoryId=14, name='new 正式店铺名称', desc='测试描述', addr='正式地址', phone='13810524086', image='/upload/item/shop/1/2017091621545314507.jpg', priority=10, createTime=2017-08-03, lastEditTime=2017-09-16, enableStatus=0, advice='审核中'}

2018-12-28 19:27:07,182 [main] DEBUG [io.github.coinsjack.dao.ShopMapper] - Cache Hit Ratio [io.github.coinsjack.dao.ShopMapper]: 0.5
Shop{id=1, ownerId=1, areaId=3, categoryId=14, name='new 正式店铺名称', desc='测试描述', addr='正式地址', phone='13810524086', image='/upload/item/shop/1/2017091621545314507.jpg', priority=10, createTime=2017-08-03, lastEditTime=2017-09-16, enableStatus=0, advice='审核中'}