Servlet
概念：http://www.runoob.com/servlet/servlet-intro.html
Servlet(for java) vs WSGI(for python)
- https://birdben.github.io/2017/03/05/Java/Python%E5%92%8CJava%E6%9C%8D%E5%8A%A1%E5%99%A8%E9%80%9A%E4%BF%A1%E5%AE%9E%E7%8E%B0%E7%9A%84%E7%90%86%E8%A7%A3%E5%92%8C%E6%AF%94%E8%BE%83/
- https://www.cnblogs.com/jackiesteed/articles/4287223.html
Spring vs Spring MVC vs Spring Boot
都遵循 Servlet 开发规范，不断抽象，降低功能层之间的耦合性，使得开发者可以站在更高的层次，更自在地编程。
http://www.springboottutorial.com/spring-boot-vs-spring-mvc-vs-spring
