1.mybatis自带缓存功能。分为一级缓存,二级缓存。
2.一级缓存为 session 缓存,在一个 session中 ,一个查询的 select 语句只会执行一次,根据 <select></select>语句的id来判断。
@Test
public void testFind() throws IOException{
SqlSession session = MybatisUtil.getSqlSession();
User user = (User)session.selectOne("cn.sxt.vo.UserMapper.findUser",1);
System.out.println(user);
System.out.println("===========================");
User u=(User)session.selectOne("cn.sxt.vo.UserMapper.findUser",1);
System.out.println(u);
session.close();
}
3.二级缓存,是 sessionFactory 级别的缓存,在 mybatis 中实现二级缓存的步骤
a) 首先实体类要序列化,二级缓存存储的是数据文件
b) 在映射中添加 cache 标签
<cache
eviction="FIFO"
flushInterval="60000"
size="512"
readOnly="true"/>
代码
@Test
public void testFind() throws IOException{
SqlSession session = MybatisUtil.getSqlSession();
User user = (User)session.selectOne("cn.sxt.vo.UserMapper.findUser",1);
System.out.println(user);
session.close();
System.out.println("===========================");
session = MybatisUtil.getSqlSession();
User u=(User)session.selectOne("cn.sxt.vo.UserMapper.findUser",1);
System.out.println(u);
session.close();
}
附:
UserMapper.xml
<?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="cn.sxt.vo.UserMapper">
<select id="findUser" resultType="User">
select * from t_user where id=#{id}
</select>
<cache
eviction="FIFO"
flushInterval="60000"
size="512"
readOnly="true"/>
</mapper>