public static void main(String[] args) {
        ResultSet resultSet = null;
        PreparedStatement preparedStatement = null;
        Connection connection = null;
        try {
            // 加载驱动
            Class.forName("com.mysql.jdbc.Driver");

            // 创建数据库连接
            String url = "jdbc:mysql://127.0.0.1:3306/mybatis_0505";
            String user = "root";
            String password = "123456";
            connection = DriverManager.getConnection(url, user, password);

            // 创建statmenet
            String sql = "SELECT * FROM tb_user WHERE id = ?";
            preparedStatement = connection.prepareStatement(sql);

            // 设置参数、执行sql，2个参数，第一个是参数的下标，从1开始，第二个参数数据查询条件数据
            preparedStatement.setLong(1, 1L);

            resultSet = preparedStatement.executeQuery();

            // 遍历结果集
            while (resultSet.next()) {
                System.out.println("ID: " + resultSet.getLong("id"));
                System.out.println("userName: " + resultSet.getString("user_name"));
                System.out.println("password: " + resultSet.getString("password"));
                System.out.println("name: " + resultSet.getString("name"));
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 释放连接（资源）
            if (null != resultSet) {
                try {
                    resultSet.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            
            if(null != preparedStatement){
                try {
                    preparedStatement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            
            if(null != connection){
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }

}

public interface UserDAO {
    
    /**
     * 根据id查询用户数据
     * 
     * @param id
     * @return
     */
    public User queryUserById(Long id);
    
    /**
     * 新增user数据
     * 
     * @param user
     */
    public void saveUser(User user);
    
    /**
     * 更新user数据
     * 
     * @param user
     */
    public void updateUser(User user);
    
    /**
     * 根据id删除用户数据
     * 
     * @param id
     */
    public void deleteUserById(Long id);

}

public class UserDAOImpl implements UserDAO{
    
    private SqlSessionFactory sqlSessionFactory;
    
    public UserDAOImpl(SqlSessionFactory sqlSessionFactory){
        this.sqlSessionFactory = sqlSessionFactory;
    }

    @Override
    public User queryUserById(Long id) {
        SqlSession session = this.sqlSessionFactory.openSession();
        User user = session.selectOne("userDAO.queryUserById", id);
        session.close();
        return user;
    }

    @Override
    public void saveUser(User user) {
        SqlSession session = this.sqlSessionFactory.openSession();
        session.insert("userDAO.saveUser", user);
        //提交事物
        session.commit();
        session.close();
    }

    @Override
    public void updateUser(User user) {
        SqlSession session = this.sqlSessionFactory.openSession();
        session.update("userDAO.updateUser", user);
        //提交事物
        session.commit();
        session.close();
    }

    @Override
    public void deleteUserById(Long id) {
        SqlSession session = this.sqlSessionFactory.openSession();
        session.delete("userDAO.deleteUserById", id);
        //提交事物
        session.commit();
        session.close();
    }

}

<mapper namespace="userDAO">

    <select id="queryUserById" resultType="cn.itcast.mybatis.pojo.User">
        SELECT *,user_name userName FROM tb_user WHERE id = #{id}
    </select>
    
    <insert id="saveUser" parameterType="cn.itcast.mybatis.pojo.User">
        INSERT INTO tb_user (
            id,
            user_name,
            password,
            name,
            age,
            sex,
            birthday,
            created,
            updated
        )
        VALUES
            (
                NULL,
                #{userName},
                #{password},
                #{name},
                #{age},
                #{sex},
                #{birthday},
                NOW(),
                NOW()
            );
    </insert>
    
    <update id="updateUser" parameterType="cn.itcast.mybatis.pojo.User">
        UPDATE tb_user
        SET 
         user_name = #{userName},
         password = #{password},
         name = #{name},
         age = #{age},
         sex = #{sex},
         birthday = #{birthday},
         updated = NOW()
        WHERE
            id = #{id}
    </update>
    
    <delete id="deleteUserById">
        DELETE FROM tb_user WHERE id = #{id}
    </delete>
    
</mapper>

public class UserDAOImplTest {

    private UserDAO userDAO;

    @Before
    public void setUp() throws Exception {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        this.userDAO = new UserDAOImpl(sqlSessionFactory);
    }

    @Test
    public void testQueryUserById() {
       User user = this.userDAO.queryUserById(1L);
       System.out.println(user);
    }

    @Test
    public void testSaveUser() {
        User user = new User();
        user.setAge(20);
        user.setBirthday(new Date());
        user.setName("test_1");
        user.setPassword("123456");
        user.setSex(1);
        user.setUserName("test_username_1");
        
        this.userDAO.saveUser(user);
    }

    @Test
    public void testUpdateUser() {
        User user = this.userDAO.queryUserById(2L);
        user.setAge(30);
        this.userDAO.updateUser(user);
    }

    @Test
    public void testDeleteUserById() {
        this.userDAO.deleteUserById(6L);
    }

}