5.1.3.22. How to add new HttpServlet to my portal without modifying the portal binary?

Actually, it is not possible but you can create a rest component instead. For more details about rest, please refer to the following article WS.

5.1.3.21. How to add new HttpSessionListeners and/or ServletContextListeners to my portal without modifying the portal binary?
5.1.3.23. How to override or add a Context Parameter to my portal without modifying the portal binary?