开发步骤：

使用maven创建项目

1.添加 Mybatis 的坐标

2.创建 user 数据表

3.编写User 实体类

4.编写映射文件 UserMapper.xml

5.编写核心文件 SqlMapConfig.xml

6.编写测试类

1.需要引入的坐标

<dependencies>
    <!--引入MySQL驱动-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.25</version>
    </dependency>
    <!--引入Mybatis-->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.1</version>
    </dependency>
    <!--引入junit测试-->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.13.2</version>
        <scope>test</scope>
    </dependency>
    <!--引入日志-->
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.14</version>
    </dependency>
</dependencies>

2.创建数据表

3.编写实体类

package com.itheibai.entity;
public class User {
    private int id;
    private String username;
    private String password;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

4.编写映射文件

在resource目录下，新建目录com.itheibai.mapper,并在目录下新建xml文件

添加约束头在xml文件中

<?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">

并配置命名空间和sql语句

<?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="userMapper">
    <select id="findAll" resultType="com.itheibai.entity.User">
        select * from user
    </select>
</mapper>

5.编写核心文件

在resource目录下，新建文件

添加核心文件约束头

<?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">

还需要配置根标签configuration，并在其中配置数据源和加载映射文件

<?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>
    <!--数据源环境-->
    <environments default="developement">
        <environment id="developement">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///test_work"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <!--加载映射文件-->
    <mappers>
        <mapper resource="com/itheibai/mapper/UserMapper.xml"></mapper>
    </mappers>

</configuration>

其中driver的值根据MySQL的版本确定，8.0及以上的版本加 cj ,以下的版本不加

6.编写测试代码

在test目录下新建测试类

在获取核心配置文件时 Resources 要用 ibatis 包下的

测试类

package com.itheibai.test;
import com.itheibai.entity.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 org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class MyBatisTest {
    @Test
    public void test1() throws IOException {
        //获得核心配置文件,导入的是相对地址
        InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
        //获取session工厂对象
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        //获得会话对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //执行操作 参数： namespace+id
        List<User> userList = sqlSession.selectList("userMapper.findAll");
        //打印数据
        System.out.println(userList);
        //释放资源
        sqlSession.close();
    }
}

调试结果：

目录结构如下：