JWT (JSON Web Token)

lets divide into chapter :
chapter 1 : What JWT actually is?
chapter 2 : structure of JWT
chapter 3 : JWT Flow
chapter 4 : creating JWT in SpringBoot
chapter 5 : JWT + RBAC Integration
chapter 6 : Common mistakes

CHAPTER 1 — What JWT actually is?
JSON Web Token is a signed token used to verify user identity without storing session data on the server.

Strip it down
JWT is just:
A string
That contains user data
And is digitally signed

What problem it solves

Without JWT: Server stores sessions → memory heavy

With JWT: Client stores token → server stays stateless

Analogy (lock this in your head)

JWT = college ID card
You carry it
College doesn’t check database every second
They just verify ID

Key idea (don’t forget)

JWT does NOT store user
JWT carries user info

stay updated for chapter 2