1、加载配置文件
 InputStream is = Resources.getResourceAsStream("mybatis-config.xml");
 2、获得session对象,接受结果
 SqlSessionfactoryBuilder builder = new SqlSessionfactoryBuilder();
 SqlSessionFactory factory = builder .build(is);
 SqlSession session = factory.openSession();
List<Dept> list = session .selectList("selectAllDept")