Microservices with Spring Boot, OAuth2, and Eureka

This project is an example of a microservices architecture built with Spring Boot, Spring Security OAuth2, Eureka Discovery, and Spring Cloud Gateway.
The system consists of 4 microservices that work together to handle authentication/authorization and securely route requests.

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Architecture

The microservices included in this solution are:

1. Discovery Server (discovery-server)

   • Implements Eureka Server.
   • Allows other microservices to dynamically register themselves.
   • Centralizes service discovery.

2. Authorization Server (auth-server)

   • Manages user login and the issuance of signed JWT tokens.
   • Centralizes authentication and authorization.
   • Clients (e.g., API Gateway) register here to use OAuth2.

3. API Gateway (api-gateway)

   • Based on Spring Cloud Gateway.
   • Responsible for routing requests to internal microservices.
   • Requires a valid JWT token for all requests.
   • Uses TokenRelay to forward the token to downstream services.

4. User Service (user-service)

   • A protected service with JWT validation.
   • Exposes a simple endpoint returning hardcoded user information (for demo purposes).
   • Does not directly depend on the Authorization Server thanks to JWT.

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Running the services

The recommended order to start the system is:

1. Discovery Server

   ./gradlew :discovery-server:bootRun

2. Authorization Server

   ./gradlew :auth-server:bootRun

3. API Gateway

   ./gradlew :api-gateway:bootRun

4. User Service

   ./gradlew :user-service:bootRun

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Testing the system

Step 1 - Obtain an access token (JWT)

Log in to the Authorization Server using an OAuth2 flow. Example (with client_id=oidc-client and client_secret=secret):

curl -X POST http://localhost:8090/oauth2/token \
  -u oidc-client:secret \
  -d "grant_type=client_credentials&scope=openid profile"

The response will include an access_token (JWT).

Step 2 - Access the protected endpoint

Using the obtained token, send a request to the User Service through the API Gateway:

curl http://localhost:8080/users/john \
  -H "Authorization: Bearer YOUR_ACCESS_TOKEN_HERE"