💬 Real-Time Chat Application

A robust, real-time chat application built with Spring Boot and Vanilla JavaScript. Features secure JWT authentication, persistent H2 file-based storage, and a responsive multi-page frontend.

• 🔐 Secure Authentication: User registration and login with JWT (JSON Web Tokens).
• 🛡️ Secure Sender Identification: Backend validates message senders based on their auth token (spoof-proof).
• 💾 Persistent Storage: Messages and Users are stored in an embedded H2 Database (file-based).
• 🔄 Real-Time Updates: Frontend polls for new messages every 3 seconds.
• 📱 Multi-Page UI: Dedicated Login/Register page and a clean Chat interface.
• 👤 User Context: Displays logged-in user's name and provides Logout functionality.

User-friendly authentication forms with validation.

Clean UI with "Logged in as..." indicator and real-time polling.

Seamless conversation flow between multiple users.

• Framework: Spring Boot 3
• Language: Java 17+
• Database: H2 Database (File Mode)
• Security: Spring Security + JWT (JJWT)
• Build Tool: Maven

• HTML5 & CSS3: Custom responsive styling with glassmorphism effects.
• JavaScript (ES6+): fetch API for REST calls, localStorage for token management.

server/src/main
├── java/com/example/chatbackend
│   ├── config/          # AppConfig (Bean definitions)
│   ├── controller/      # AuthController, ChatController
│   ├── model/           # User, Message Entities
│   ├── repository/      # UserRepository, MessageRepository
│   ├── security/        # JwtFilter, SecurityConfig
│   ├── service/         # AuthService, ChatService
│   └── ChatBackendApplication.java
└── resources
    ├── application.properties # DB & JWT Config
    └── data/            # H2 Database files

client/
├── index.html       # Main Chat Interface (Protected)
├── login.html       # Login & Register Forms
├── script.js        # Auth logic, Polling, DOM manipulation
└── style.css        # Styling & Responsive Design

• JDK 17 or higher
• Maven

Navigate to the server directory and run the application:

cd server
mvn spring-boot:run

The server will start at http://localhost:8080.

Simply open the client/login.html file in your modern web browser.

1. Register a new account.
2. Login with your credentials.
3. Start Chatting! (Open a second window/browser to test multiple users).

You can configure JWT settings and Database path in application.properties:

# JWT Configuration
jwt.secret=your_very_long_secret_key_here...
jwt.expiration=86400000

# Database
spring.datasource.url=jdbc:h2:file:./src/main/resources/data/chatdb