前言：

这是用来这篇文章的参考代码（超链接）

一、示例代码图

二、代码例子

1.接口类–boyMapper

package com.project.Mapper;

import com.project.pojo.Boy;

import java.util.List;

public interface boyMapper {

    //1.定义一个查询全部的方法
    //List<封装类> 查询全部的方法
   List<Boy>  selectAll();
}

2.封装类–Boy

package com.project.pojo;

public class Boy {
    private Integer id;

    private String name;

    private Integer age;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Boy(Integer id, String name, Integer age) {
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public Boy() {
    }

    @Override
    public String toString() {
        return "boy{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

3.测试类—BoyTest

package com.project.pojo;

import com.project.Mapper.boyMapper;
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 BoyTest {
    public static void main(String[] args) throws IOException {
        //1.加载mybatis连接文件（核心配置文件）
        String resource = "mybatis-config.xml";//这是连接数据库的统一配置xml文件
        InputStream inputStream = Resources.getResourceAsStream(resource);//固定写法
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//固定写法

        //2.获取SqlSessionFactory对象--固定写法
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //3.执行sql语句
        //接口 自定义接口名 = sqlSession.getMapper(接口.class);
        boyMapper boyMapper = sqlSession.getMapper(boyMapper.class);

        //接口里面的方法
        List<Boy> boyAll = boyMapper.selectAll();

        //4.打印语句
        System.out.println(boyAll);

        //5.释放资源--固定写法
        sqlSession.close();
    }
}

4.映射文件–boyMapper.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">

<!--映射查询方法-->
<mapper namespace="com.project.Mapper.boyMapper"><!--namespace=对应接口的全部路径-->
    <select id="selectAll" resultType="com.project.pojo.Boy"><!--参数一：接口对应的方法名    参数二：封装类的详细地址-->
        select * from boy;<!--要执行的sql语句-->
    </select>
</mapper>

5.统一配置文件–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">
                <!--数据库信息-->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/><!--改：数据库的固定连接，老版本不用cj-->
                <property name="url" value="jdbc:mysql://localhost:3306/javafx"/><!--改数据库的要连接的库-->
                <property name="username" value="root"/><!--改：数据库的账号-->
                <property name="password" value="123456"/><!--改：数据库的密码-->
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--加载映射文件-->
        <mapper resource="com/project/Mapper/boyMapper.xml"/><!--改：把映射文件的源根路径复制到这里-->
    </mappers>
</configuration>

6.依赖文件–pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    
    <groupId>org.example</groupId>
    <artifactId>maven-java</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <maven.compiler.source>17</maven.compiler.source>
        <maven.compiler.target>17</maven.compiler.target>
    </properties>
    
<!--mybatis需要的依赖包-->
    <dependencies>
        <!--mybatis依赖包-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.11</version>
        </dependency>

        <!--mysql依赖包-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.30</version>
        </dependency>
    </dependencies>

</project>