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  • java之mybatis之缓存

    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>
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  • 原文地址:https://www.cnblogs.com/Vincent-yuan/p/11297670.html
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