一. 接口方式

1.创建接口

public interface UserDao {    
    User selectUserById(int id);
}

2.User.xml

<?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="com.souke.mybatis.dao.UserDao">
    <select id="selectUserById" parameterType="int" resultType="User">
        select * from user where id = #{id}
    </select>
</mapper>

3.测试

public static void main(String[] args) {
  SqlSession session = sqlSessionFactory.openSession();
  UserDao userDao = session.getMapper(UserDao.class);
  User user = userDao.selectUserById(1);
  System.out.println(user.getName());
  session.close();
}

ps:User.xml 中的namepace路径要设置成UserDao的路径。

二.注解方式

1.创建接口

public interface UserDao {    
  @Select("select * from user where id = #{id}")    
  User selectUserById(int id);
}

2.测试

    public static void main(String[] args) {

        sqlSessionFactory.getConfiguration().addMapper(UserDao.class);

        SqlSession session = sqlSessionFactory.openSession();
        UserDao userDao = session.getMapper(UserDao.class);
        User user = userDao.selectUserById(1);
        System.out.println(user.getName());
        session.close();
    }

ps:User.xml不需要。这样子就可以进行正常运行，显示结果。