参考：MyBatis的通俗理解：SqlSession.getMapper()源码分析

笔记：

1. SqlSession中可以通过getMapper()拿到代理对象，SqlSession.getMapper 运用了 JDK动态代理，产生了目标Mapper接口的代理对象。

    public void getUserByLimit(){
   
           SqlSession sqlSession = MybatisUtils.getSqlSession();
           UserMapper mapper = sqlSession.getMapper(UserMapper.class);
   
           HashMap<String, Integer> map = new HashMap<String, Integer>();
           map.put("startIndex",0);
           map.put("pageSize",2);
   
           List<User> userList =  mapper.getUserByLimit(map);
           for (User user : userList) {
               System.out.println(user);
           }
   
           sqlSession.close();