💰 Wallet Application

A full-stack digital wallet application built with Java Spring Boot backend and vanilla HTML/CSS/JavaScript frontend. Users can register, log in, check their balance, and send money to other users.

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✨ Features

• User Registration — Sign up with email & password, receive ₹1000 starting balance
• User Login — Authenticate with email and password
• Balance Dashboard — View current wallet balance in real-time
• Money Transfer — Send money to any registered user
• Error Handling — Prevents self-transfers, insufficient balance, duplicate accounts, and invalid credentials
• Transactional Safety — Money transfers use @Transactional for atomicity

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🛠️ Tech Stack

Layer	Technology
Backend	Java 17+, Spring Boot 3.2.5
Database	H2 (in-memory relational DB)
ORM	Spring Data JPA / Hibernate
Frontend	HTML5, CSS3, Vanilla JavaScript
API Format	RESTful JSON
Build Tool	Maven 3.9.6 (wrapper included)

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📁 Project Structure

Wallet/
├── README.md
├── backend/
│   ├── pom.xml
│   ├── mvnw.cmd
│   ├── .mvn/wrapper/
│   └── src/main/
│       ├── java/com/wallet/
│       │   ├── WalletApplication.java          # Spring Boot entry point
│       │   ├── model/
│       │   │   └── User.java                   # JPA Entity (id, email, password, balance)
│       │   ├── repository/
│       │   │   └── UserRepository.java         # Spring Data JPA Repository
│       │   ├── service/
│       │   │   └── WalletService.java          # Business logic with @Transactional
│       │   ├── controller/
│       │   │   └── WalletController.java       # REST API endpoints
│       │   └── config/
│       │       └── WebConfig.java              # CORS configuration
│       └── resources/
│           ├── application.properties          # H2 & JPA configuration
│           └── static/                         # Frontend served by Spring Boot
│               ├── login.html
│               ├── dashboard.html
│               ├── send.html
│               └── style.css
└── frontend/                                   # Standalone frontend files
    ├── login.html
    ├── dashboard.html
    ├── send.html
    └── style.css

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🚀 Getting Started

Prerequisites

• Java 17 or higher installed (Download)
• No Maven installation needed — Maven wrapper is included

Run the Application

# Clone the repository
git clone https://github.com/atharv01h/Wallet-App.git
cd wallet-app/backend

# Start the Spring Boot server (Windows)
.\mvnw.cmd spring-boot:run

# Start the Spring Boot server (Linux/Mac)
./mvnw spring-boot:run

Note: First run downloads all dependencies and may take a few minutes. Subsequent runs are much faster.

Open in Browser

Navigate to: http://localhost:8080/login.html

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📡 API Endpoints

Method	Endpoint	Description	Request Body
POST	/api/register	Register a new user	{ "email": "...", "password": "..." }
POST	/api/login	Login with credentials	{ "email": "...", "password": "..." }
GET	/api/balance?email=...	Get wallet balance	—
POST	/api/send	Transfer money	{ "fromEmail": "...", "toEmail": "...", "amount": 100 }

Example API Usage (cURL)

# Register
curl -X POST http://localhost:8080/api/register \
  -H "Content-Type: application/json" \
  -d '{"email":"alice@wallet.com","password":"pass123"}'

# Login
curl -X POST http://localhost:8080/api/login \
  -H "Content-Type: application/json" \
  -d '{"email":"alice@wallet.com","password":"pass123"}'

# Check Balance
curl http://localhost:8080/api/balance?email=alice@wallet.com

# Send Money
curl -X POST http://localhost:8080/api/send \
  -H "Content-Type: application/json" \
  -d '{"fromEmail":"alice@wallet.com","toEmail":"bob@wallet.com","amount":250}'

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🖥️ Application Pages

Login / Register

• Enter email and password
• Click "Create Account" to register (₹1000 default balance)
• Click "Sign In" to log in

Dashboard

• View your current wallet balance
• Navigate to send money or logout
• Refresh balance button for real-time updates

Send Money

• Enter recipient's email and amount
• Submit to transfer funds instantly
• Error messages shown for invalid operations

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⚙️ Business Rules

Rule	Description
Default Balance	New users receive ₹1000 on registration
Self-Transfer	Cannot send money to yourself
Insufficient Funds	Cannot send more than your available balance
Duplicate Email	Cannot register with an already-used email
Positive Amount	Transfer amount must be greater than zero

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🗄️ Database

The app uses H2 in-memory database — all data resets on server restart.

• H2 Console: http://localhost:8080/h2-console
  • JDBC URL: jdbc:h2:mem:walletdb
  • Username: sa
  • Password: (leave empty)

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🏗️ Architecture

┌─────────────┐     HTTP/JSON     ┌──────────────────────────────────────┐
│   Frontend   │ ◄──────────────► │           Spring Boot Backend        │
│  (HTML/JS)   │                  │                                      │
│              │                  │  Controller → Service → Repository   │
│  login.html  │                  │      ↓           ↓          ↓        │
│  dashboard   │                  │  REST API    Business    JPA/H2 DB   │
│  send.html   │                  │              Logic                   │
└─────────────┘                  └──────────────────────────────────────┘

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📝 License

This project is open source and available for educational purposes.

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👨‍💻 Created By

Atharv Hatwar