This document outlines key concepts for web applications including the directory structure with WEB-INF, classes, and lib folders, as well as concepts like servlets, GET and POST requests, sessions, filters, event listeners, and cookies. It discusses the basics of processing user actions, GET requests via the URL, POST requests sending binary data, and using sessions, filters, event listeners, and cookies within web applications.

1. Day 20

2. .WAR

3. document root directory|-- WEB-INF |--classes |--lib|-- META-INF |-- manifest.mf

4. Servlets

6. new Servlet();

7. User action processing

8. HTTP GET & POST

9. GET - URL

10. POST - Binary

11. Session

12. Filters

13. Event Listeners

14. Cookies