shiro源码阅读
官网：http://shiro.apache.org/session-management.html#SessionManagement-StatelessApplications%28Sessionless%29
参见：https://www.cnblogs.com/youzhibing/p/9866690.html
参见：https://www.iteye.com/blog/jinnianshilongnian-2018398
较为细致的源码解释：https://www.yht7.com/news/11221
doFilter与doFilterInternal的区别 参见：https://www.cnblogs.com/sjxbg/p/13475387.html
