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

在这里插入图片描述

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 mapper
        PUBLIC "-//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 configuration
        PUBLIC "-//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mybatis
        String 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sql
        List<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;
    }