MyBatis和jdbc关联
InputStream//程序输入流,加载xml文件(定义jdbc链接信息)
InputStream in = Demo.class.getResourceAsStream("/MyBatisConfiguration.xml");
SqlSessionFactory sf = new SqlSessionFactoryBuilder().build(in);//导老版本的Mybatis包
SqlSession:封装了jdbc的方法!CURD;
SqlSession session = sf.openSession();