Spring Boot JWT Authentication & SSO API

This project is a centralized Identity Provider (IdP). It uses JWT (JSON Web Tokens) to secure multiple applications. It comes with Global CORS enabled, making it ready to serve as a Single Sign-On (SSO) backend for your frontend apps (React, Vue, etc.).

Features

• User Login (/api/login) → Returns JWT
• Protected Endpoints (e.g., /api/hello) → Requires JWT
• BCrypt Password Encoding
• Stateless Authentication (No Sessions)
• CORS Enabled (Ready for external frontends)
• Database Support: H2 (In-memory) or MySQL/PostgreSQL (Cloud/Aiven)

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Prerequisites

Before you begin, ensure you have the following installed:

• Java 17 or higher
• Maven (optional, wrapper provided)
• Git

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Project Structure

src/main/java/com/example/demo
├── config/
│   └── CorsConfig.java          # Global CORS settings (who can access this API)
├── exception/
│   ├── GlobalExceptionHandler.java # Returns nice JSON errors (401, 500)
│   └── InvalidCredentialsException.java
├── AppUser.java                 # User entity (Database table)
├── AuthController.java          # Login endpoints
├── AuthService.java             # Business logic for authentication
├── JwtUtil.java                 # Generates & validates Tokens
└── SecurityConfig.java          # Spring Security rules (Authorized vs Public)

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Setup & Run

1. Clone & Build

git clone https://github.com/ezManish/Auth_API.git
cd Auth_API
mvn clean spring-boot:run

The API will start on http://localhost:8080 (default).

2. Database Configuration

By default, it runs on H2 (In-memory). To connect to a real database (like Aiven), update src/main/resources/application.properties:

For Aiven (MySQL):

spring.datasource.url=jdbc:mysql://YOUR-AIVEN-URL:PORT/defaultdb?ssl-mode=REQUIRED
spring.datasource.username=avnadmin
spring.datasource.password=YOUR_PASSWORD
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.jpa.hibernate.ddl-auto=update

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API Endpoints

1. Login (Get Token)

• URL: POST /api/login
• Body:

  {
    "username": "student1",
    "password": "pass123"
  }

• Response (200 OK): eyJhbGciOiJIUzI... (The Token)
• Response (401 Unauthorized): Invalid username or password

2. Access Protected Resource

• URL: GET /api/hello
• Headers:

  Authorization: Bearer <YOUR_JWT_TOKEN>
  

• Response: Hello, you are authenticated with JWT!

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Integration Guide (SSO)

You can use this API as the login backend for multiple other projects (Project A, Project B).

How to Connect (Frontend/JS)

1. Login: Call POST /api/login to get the token.
2. Save Token: Store it in localStorage.
3. Use Token: Send it in the header for every future request.

Example (Fetch API):

// A. LOGIN
const response = await fetch('http://localhost:8080/api/login', {
  method: 'POST',
  body: JSON.stringify({ username: 'user', password: 'password' }),
  headers: { 'Content-Type': 'application/json' }
});
const token = await response.text();
localStorage.setItem('jwt', token);

// B. ACCESS
await fetch('http://localhost:8080/api/hello', {
  headers: { 'Authorization': `Bearer ${token}` }
});

SSO Configuration Checklist

If you have other backend services (Project A, Project B) that need to valid users:

Setting	Auth API (Hub)	Project A / B (You)
Database Credentials	YES	NO
JWT Secret Key	YES (Create Token)	YES (Verify Token)

Important: Copy the jwt.secret from this project's application.properties to your other projects so they can verify the tokens are valid.

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Troubleshooting

1. "Address already in use"

• Cause: Port 8080 is blocked.
• Fix: Open application.properties and add server.port=8082.

2. "Connection refused" to Database

• Cause: Wrong URL or Password in application.properties.
• Fix: Double-check your Aiven credentials. Ensure SSL is enabled (?ssl-mode=REQUIRED).

3. "Cross-Origin Request Blocked" (CORS)

• Cause: Frontend is on a different domain.
• Fix: This project allows * by default. If it fails, check CorsConfig.java to ensure your specific domain is allowed.