This is an advanced microservices project that includes the following:

 - An OAuth2 server to authenticate and authorize users.
   Key software used: Spring Authorization server

 - An API gateway that implements the Backend for Frontend (BFF) application architecture.
   Key software used: Spring Cloud API Gateway (Webflux)

 - An OAuth2 resource server that exposes REST endpoints.
   
 - A React.js frontend application that interacts with the API gateway.

References:

 - The pattern used in this application is detailed here.
   https://www.baeldung.com/spring-cloud-gateway-bff-oauth2

 - Details about Backend for Frontend application architecture
   https://datatracker.ietf.org/doc/html/draft-ietf-oauth-browser-based-apps#name-application-architecture-pa

 - OAuth2 authorization framework
   https://datatracker.ietf.org/doc/html/rfc6749

 - OpenID
   https://openid.net/

Ports used:

  8050 - API gateway
  8051 - OAuth2 server
  8052 - Resource server

URLs used:

Both the API gateway and the OAuth2 server are accessed by the web browser and for each of them, a session is maintained. To avoid API gateway session data being sent to the OAuth2 server while a developer runs both servers locally, they are accessed via http://localhost and http://127.0.0.1 respectively.