参考文章：
https://www.cnblogs.com/51kata/p/5152400.html
http://www.cnblogs.com/fangjian0423/p/servletContainer-tomcat-urlPattern.html
Servlet容器Tomcat中web.xml中url-pattern的配置详解[附带源码分析]
https://blog.csdn.net/mengxiangxingdong/article/details/80623522