tomcat深入学习

总体结构：https://www.jianshu.com/p/d74eef07487f

servlet相关：https://www.ibm.com/developerworks/cn/java/j-lo-servlet/

实力不够，看不懂：https://www.ibm.com/developerworks/cn/java/j-lo-tomcat1/，https://www.ibm.com/developerworks/cn/java/j-lo-tomcat2/