Building Secure Microservices: OAuth2 + JWT Role-Based Access Control in Action

Learn how to implement OAuth2 authentication with role-based access control across microservices. In this demo, I walk through generating JWT tokens using Postman and show how protected endpoints enforce authorization based on user roles (ADMIN, SELLER, USER).

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

WHAT YOU'LL LEARN

- How to configure OAuth2 Authorization Code flow in Postman
- Understanding JWT structure and role claims
- Implementing @PreAuthorize for endpoint security
- How Resource Servers validate tokens via JWKS
- Handling 401 Unauthorized and 403 Forbidden responses

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

ARCHITECTURE

User Service (Authorization Server)
- Issues JWT tokens with embedded role claims
- Exposes JWKS endpoint for public key distribution
- Handles OAuth2 flows: Authorization Code, Client Credentials, Refresh Token

Product Service (Resource Server)
- Validates JWTs using public keys from JWKS
- Enforces RBAC with Spring Security @PreAuthorize
- Protected endpoints for product and category management

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

TECH STACK

- Java 21
- Spring Boot 4.x
- Spring Authorization Server
- Spring Security (OAuth2 Resource Server)
- MySQL + Flyway Migrations
- RSA 2048-bit Token Signing

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

KNOWN LIMITATIONS & EDGE CASES

- RSA keys regenerate on application restart (invalidates existing tokens)
- No rate limiting on authentication endpoints
- Refresh token rotation not implemented
- PKCE not enabled for public clients
- Security headers (HSTS, CSP) not configured

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

SOURCE CODE

User Service (Auth Server): https://github.com/spa-raj/userservice
Product Service (Resource Server): https://github.com/spa-raj/productservice

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

RELATED TOPICS

OAuth 2.0, OpenID Connect, JWT, JSON Web Tokens, Spring Security, Microservices Authentication, Role-Based Access Control, RBAC, Authorization Server, Resource Server, API Security, Postman OAuth2

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

#OAuth2.0 #SpringBoot #JWT #Microservices #Java #SpringSecurity #APIAuthentication #RBAC

Видео Building Secure Microservices: OAuth2 + JWT Role-Based Access Control in Action канала Sparsh Raj