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Secured Microservices — OAuth2 / OIDC / Keycloak

Secured e-commerce microservices where Keycloak is the central authorization server. Two Spring Boot resource servers (inventory, order) validate Keycloak-issued JWTs; order-service calls inventory via OpenFeign with bearer-token propagation; an Angular client logs in via OIDC.

View Code
2
Resource servers
Keycloak
Identity provider
OpenFeign
Inter-service
Angular OIDC
Client
Approach

Keycloak as central IdP; JWT resource servers + role-mapping converter + Feign token propagation

Tech Stack
Java 17Spring Boot 3.2Spring SecurityKeycloakOAuth2/OIDCOpenFeignAngularH2Swagger
Keywords
KeycloakOAuth2OIDCJWTSpring SecurityOpenFeignAngularMicroservices
Deep Dive

A focused study of OAuth2 / OpenID Connect security for microservices, with Keycloak as the identity provider for an e-commerce domain.

Architecture

                    ┌──────────────┐
                    │   Keycloak   │  realm: sdia-realm  (:8080)
                    │ (OAuth2/OIDC)│
                    └──────┬───────┘
                           │ JWT (Bearer)
        ┌──────────────────┼──────────────────────────┐
        ▼                  ▼                            ▼
  ┌───────────────┐  ┌───────────────────┐     ┌───────────────┐
  │  ecom-app     │  │  order-service     │ ──► │  inventory-   │
  │  (Angular)    │  │  :8088 (OpenFeign) │     │  service :8087│
  └───────────────┘  └───────────────────┘     └───────────────┘
                     propagates the token via FeignInterceptor

Security details

  • ▸SecurityConfig registers each service as a resource server (oauth2ResourceServer().jwt())
  • ▸JwtAuthConverter converts Keycloak realm/client roles into Spring Security authorities
  • ▸FeignInterceptor on order-service forwards the bearer token to inventory-service
  • ▸Both services use H2 in-memory databases; order-service ships Swagger UI

Modules: inventory-service (products, :8087) · order-service (orders, :8088) · ecom-app-angular (OIDC login client, :4200).

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