黑马Mybatis

Mybatis

表现层：页面展示
业务层：逻辑处理
持久层：持久数据化保存

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Mybatis快速入门

![在这里插入图片描述](https://i-blog.csdnimg.cn/direct/6501c2109c4442118ceb6014725e48e4.png

//logback.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration><!--CONSOLE ：表示当前的日志信息是可以输出到控制台的。--><appender name="Console" class="ch.qos.logback.core.ConsoleAppender"><encoder><pattern>[%level]  %cyan([%thread]) %boldGreen(%logger{15}) - %msg %n</pattern></encoder></appender><logger name="com.itheima" level="DEBUG" additivity="false"><appender-ref ref="Console"/></logger><!--level:用来设置打印级别，大小写无关：TRACE, DEBUG, INFO, WARN, ERROR, ALL 和 OFF， 默认debug<root>可以包含零个或多个<appender-ref>元素，标识这个输出位置将会被本日志级别控制。--><root level="DEBUG"><appender-ref ref="Console"/></root>
</configuration>

//UserMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace:名称空间
-->
<mapper namespace="test"><select id="selectAll" resultType="com.itheima.pojo.User">select * from tb_user;</select>
</mapper>

mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN""https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration><environments default="development"><environment id="development"><transactionManager type="JDBC"/><dataSource type="POOLED">
<!--                数据库连接信息--><property name="driver" value="com.mysql.cj.jdbc.Driver"/><property name="url" value="jdbc:mysql:///db01?useSSL=false"/><property name="username" value="root"/><property name="password" value="123456"/></dataSource></environment></environments><mappers>
<!--        加载sql映射文件-->
<!--        <mapper resource="UserMapper.xml"/>-->
<!--        mapper代理方式--><package name = "com.itheima.mapper"/></mappers>
</configuration>

//MybatisDemo.java
package com.itheima;import com.itheima.pojo.User;
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;public class MyBatisDemo {/*** mybatis快速入门*/public static void main(String[] args) throws IOException {//1.加载mybatisString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取sqlSession对象SqlSession sqlsSession = sqlSessionFactory.openSession();//3.执行sqlList<User> users = sqlsSession.selectList("test.selectAll");System.out.println(users);//4.释放资源}
}

User
package com.itheima.pojo;// alt + 左边
public class User {private String id       ;private String username ;public String getId() {return id;}