SecurityManager 单例模式 - 国内版 Bing
https://cn.bing.com/search?q=SecurityManager+单例模式&qs=n&form=QBRE&sp=-1&pq=securitymanager+单例模式&sc=0-20&sk=&cvid=708294EC7BC24E4DA0FA15AA05329F35
Java安全之SecurityManager
https://nicky-chen.github.io/2018/07/13/java-securitymanager/
Shiro学习（二）——读取配置文件与初始化SecurityManager的过程_sadoshi的专栏-CSDN博客
https://blog.csdn.net/sadoshi/article/details/108096833
SecurityManager怎么实现防止暴力反射-CSDN社区
https://bbs.csdn.net/topics/390559224