升级以后的DAO及相关类的测试

https://www.bilibili.com/video/BV1eJ411c7rf?p=45

加入泛型

https://github.com/jihch/jdbc_2/blob/main/src/main/java/io/github/jihch/betterdao/BaseDAO.java

https://github.com/jihch/jdbc_2/blob/main/src/main/java/io/github/jihch/betterdao/CustomerDAO.java

https://github.com/jihch/jdbc_2/blob/main/src/main/java/io/github/jihch/betterdao/CustomerDAOImpl.java