Mybatis的一二级缓存，一级缓存默认开启

Posted 2021-09-06 SmallCuteMonkey

1.可以知道的是Mybatis的一级缓存SqlSession默认是开启的。

2.可以自己去开启二级缓存在config.xml文件中的properties下面可以加上这个配置：

  <settings>
        <!--进行懒加载-->
        <setting name="lazyLoadingEnabled" value="false"/>
        <!-- 开启缓存-->
        <setting name="cacheEnabled" value="true"/>
    </settings>

3.可以知道缓存之后的同一个session，再次执行操作的时候是不用再次查询数据库的。

resources下面建立这几个文件：
db.properties:

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/csjzjj
jdbc.username=root
jdbc.password=roothouzhicong

config.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

    <properties resource="db.properties"></properties>
	<environments default="development">
		<environment id="development">
		<transactionManager type="jdbc"></transactionManager>
		<dataSource type="POOLED">
		 <property name="driver" value="${jdbc.driver}"/>
         <property name="url" value="${jdbc.url}"/>
         <property name="username" value="${jdbc.username}"/>
         <property name="password" value="${jdbc.password}"/>
		</dataSource>
		</environment>
	</environments>
	
	<mappers>
     <!--要使用注解方式-->
      <mapper class="com.zjj.mapper.MyUserMapper"></mapper>
	</mappers>

</configuration>

MyUserMapper:

package com.zjj.mapper;

import com.zjj.entity.MyUser;
import org.apache.ibatis.annotations.Select;

import java.util.List;

/**
 * @Program mybatis
 * @Package com.zjj.mapper
 * @Auther TeacherHuang
 * @Date 2021/8/16 15:29
 * @Version 1.0
 */
public interface MyUserMapper {

    @Select("select *from myuser")
    List<MyUser> selectAll() throws  Exception;

    @Select("select *from myuser")
    List<MyUser> selectAll01() throws  Exception;
}

Test:

import com.zjj.entity.MyUser;
import com.zjj.mapper.MyUserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * @Program mybatis
 * @Package PACKAGE_NAME
 * @Auther TeacherHuang
 * @Date 2021/8/16 15:31
 * @Version 1.0
 */
public class Test {
    public static void main(String[] args) throws Exception {
        String resources="config.xml";
        InputStream inputstream = Resources.getResourceAsStream(resources);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputstream);
        SqlSession session = sqlSessionFactory.openSession(true);
        System.out.println(session);



       MyUserMapper myUserMapper = session.getMapper(MyUserMapper.class);
         System.out.println("第一次没有缓存数据的时候---------------------");
        List<MyUser> myUsers = myUserMapper.selectAll();
        System.out.println(myUsers);

//        session.close();
          session.clearCache();

        System.out.println("第二次没有缓存数据的时候---------------------");
        MyUserMapper myUserMapper02 = session.getMapper(MyUserMapper.class);
        List<MyUser> myUsers01 = myUserMapper.selectAll();
        System.out.println(myUsers01);




    }
}