Stateless Authentication in SpringBoot with JWT: Complete Implementation Guide

In distributed micro‑service architectures, traditional session‑based authentication suffers from state coupling, poor scalability, cross‑origin issues and security risks. JWT (JSON Web Token) provides a stateless solution where the server stores no session data.

Why choose JWT?

Stateless, easy to scale across clusters.

Cross‑origin friendly – token passed in headers.

Can carry non‑sensitive user info, reducing DB lookups.

Signed and optionally encrypted, high security.

Works on web, mobile, mini‑programs.

JWT core structure

A JWT consists of three Base64‑encoded parts separated by dots: header.payload.signature.

Header

Specifies token type and signing algorithm (e.g., HS256 or RS256). The header is Base64‑encoded; it is not encrypted.

Payload

Contains claims. Standard claims include iss, sub, iat, exp, aud. Custom claims can store username, role, nickname, etc. Payload is also Base64‑encoded and therefore readable.

Signature

Generated by signing Base64(header) + "." + Base64(payload) with the secret key (HS256) or private key (RS256). The server validates the signature to ensure integrity.

Double‑token scheme

Because a JWT cannot be revoked before expiration, a common pattern is to issue an AccessToken (short‑lived, 15‑30 min) and a RefreshToken (long‑lived, 7‑30 days). When the access token expires, the client sends the refresh token to obtain a new access token without re‑login.

Logout with Redis blacklist

On logout, both tokens are stored in Redis with an expiration equal to the token’s remaining lifetime. Subsequent requests check the blacklist; if a token is found, access is denied.

Environment preparation

SpringBoot 2.7.10

jjwt‑api/impl/jackson 0.11.5

Redis 6.2.6 (StringRedisTemplate)

Maven, Lombok, IDEA, Postman

Key code

pom.xml dependencies (SpringBoot Web, jjwt, Redis, Lombok, test).

application.yml defines Redis connection and JWT parameters (secret ≥ 32 bytes, expiration times, header name, prefix).

JwtUtil – generates and validates tokens, extracts claims, username and expiration.

RedisUtil – adds tokens to blacklist, checks existence, removes entries.

AuthController implements three endpoints: POST /auth/login – validates hard‑coded credentials, returns access and refresh tokens. POST /auth/refresh – validates refresh token, issues new access token. POST /auth/logout – removes both tokens from Redis blacklist.

LoginInterceptor intercepts all requests, extracts the token from the configured header, removes the prefix, validates the token and checks the blacklist, returning JSON error messages for missing, expired or revoked tokens.

WebConfig registers the interceptor for all paths except /auth/login and /auth/refresh, and configures CORS for front‑end separation.

Testing workflow

Login via POST /auth/login to obtain accessToken and refreshToken.

Call a protected endpoint (e.g., GET /user/info) with header Authorization: Bearer <accessToken>.

When the access token expires, call POST /auth/refresh with the refresh token to get a new access token.

Logout via POST /auth/logout sending the access token header and refresh token parameter; subsequent calls with either token return 401.

This guide provides a complete, production‑ready implementation of stateless JWT authentication in SpringBoot, covering theory, code, configuration and end‑to‑end testing.