一、搭建环境

创建数据库表

CREATE TABLE `user` (
  `id` int(20) NOT NULL,
  `name` varchar(30) DEFAULT NULL,
  `password` varchar(30) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO `user` (`id`, `name`, `password`) VALUES
(1, '内河', '123456'),
(2, '张三', '123456'),
(3, '李四', '123456');

新建项目

导入依赖

<dependencies>
    <!--junit依赖  -->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <!--mybatis依赖  -->
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.5.6</version>
    </dependency>
    <!--mysql依赖  -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.11</version>
    </dependency>
  </dependencies>

二、创建一个模块

在resources文件夹下编写Mybatis的核心配置文件mybatis-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核心配置文件-->
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
								<!--导入jdbc-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
								<!--数据库链接-->
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSl=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC"/>
	              <!--数据库用户名-->
								<property name="username" value="root"/>
								<!--数据库密码-->
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

<!--每一个mapper.xml都需要在Mybatis核心文件中注册！-->
<mappers>
		<!--注册地址-->
    <mapper resource="top/ltyzqhh/dao/UserMapper.xml"/>
</mappers>
</configuration>

编写Mybatis工具类

package top.ltyzqhh.utils;

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;

//sqlSeessionFactory-->sqlSession

public class Mybatis_utils {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            //工具类第一步：获取sqlSesscionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
             sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }

        //有了sqlSessionFactory，就可以从中获得SqlSession的实例
        //SqlSession完全包含了面向数据库执行SQL命令所需要的所有方法
    }
    public  static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }

}

编写实体类

package top.ltyzqhh.pojo;

public class User {
        private int id;
        private String name;
        private String password;

    public User() { }

    public User(int id, String name, String password) {
        this.id = id;
        this.name = name;
        this.password = password;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

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

编写一个接口

public interface UserDao {
    List<User> getUserList();
}

接口实现类由原来的UserDaoImpl转变为一个Mapper配置文化

<?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>">

<!--命名空间namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="top.ltyzqhh.dao.UserDao">
    
    <!--id=接口的方法名字，resultType=返回单个结果集 resultMap=多个结果集，-->
    <select id="getUserList" resultType="top.ltyzqhh.pojo.User">
        select * from mybatis.user;
    </select>
</mapper>

三、测试

junit测试