配置类如下

核心配置文件

<?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核心配置文件-->
<configuration>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;useUnicode=true&amp;characterEncoding=Utf-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

<!--    每一个Mapper.xml都需要在Mybatis核心配置文件中注册！-->
    <mappers>
        <mapper resource="com/kuang/dao/UserMapper.xml"/>
    </mappers>

</configuration>

sqlSession配置文件

//sqlSessionFactory --> sqlSession
public class MybatisUtils {

    private static SqlSessionFactory sqlSessionFactory;
    static {
        try {
            //使用Mybatis第一步：获取sqlSessionFactory对象
            String resource = "mybatis-config.xml";
            InputStream inputStream;
            inputStream = Resources.getResourceAsStream(resource);
            SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    // 既然有了 SqlSessionFactory，顾名思义，我们可以从中获得 SqlSession 的实例。
    // SqlSession 提供了在数据库执行 SQL 命令所需的所有方法。

    public static SqlSession getSqlSession(){
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }

}

编写代码

• 实体类

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

    public User() {
    }

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


    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 getPwd() {
        return pwd;
    }

    public void setPwd(String pwd) {
        this.pwd = pwd;
    }


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

• Dao接口

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

• 接口实现类由原来的UserDaoImpl转变为一个Mapper文件

<?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">

<!--绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.kuang.dao.UserDao">
    <select id="getUserList" resultType="com.kuang.pojo.User">
        select * from mybatis.user
    </select>
</mapper>

测试

注意点：org.apache.ibatis.binding.BindingException: Type interface com.kuang.dao.UserDao is not known to the MapperRegistry.

核心配置文件中注册mappers

• junit

@Test
public void test(){
    //获取SqlSession对象
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    //执行SQL
    UserDao mapper = sqlSession.getMapper(UserDao.class);
    List<User> userList = mapper.getUserList();

    for (User user : userList) {
        System.out.println(user);
    }
    
    //关闭SqlSession
    sqlSession.close();
}

可能会遇到的问题： 1.配置文件没有注册 2.绑定接口错误 3.方法名不对 4.返回类型不对 5.Maven导出出问题

梳理一下思路：

连接数据库->导入所需要的jar包->建造SqlSession对象(工具类)->配置xml使代码可以连接数据库->实体类，接口，Mapper.xml