Digital Wallet System

A comprehensive backend implementation for digital wallet operations built with Spring Boot. This application provides secure user authentication, account management, peer-to-peer payments, and a marketplace for digital products.

Features

• User Management - Registration and authentication with secure password encryption
• Wallet Operations - Fund accounts and check balances with multi-currency support
• Payment System - Peer-to-peer money transfers with real-time balance updates
• Product Marketplace - Buy and sell digital products using wallet balance
• Transaction History - Complete audit trail with detailed transaction records
• Security - Spring Security integration with input validation

Technology Stack

• Framework: Spring Boot 3.5.3
• Language: Java 21
• Database: PostgreSQL (Neon)
• Security: Spring Security with BCrypt
• Build Tool: Maven
• Architecture: RESTful API

Live Application

The application is deployed and accessible at:

https://digital-wallet-backend-service.onrender.com/api/v1

Deployed on Render cloud service for easy access and testing.

Documentation

For complete API documentation with all endpoints, request/response formats, and examples, visit: API Documentation

Quick Test

Test the API with these sample requests:

# Register a user
curl -X POST https://digital-wallet-backend-service.onrender.com/api/v1/register \
  -H "Content-Type: application/json" \
  -d '{"username":"demo","password":"demo123"}'

# Fund account (use Basic Auth: demo:demo123)
curl -X POST https://digital-wallet-backend-service.onrender.com/api/v1/fund \
  -H "Content-Type: application/json" \
  -H "Authorization: Basic ZGVtbzpkZW1vMTIz" \
  -d '{"amt":100.00}'

# Check balance
curl -X GET https://digital-wallet-backend-service.onrender.com/api/v1/bal \
  -H "Authorization: Basic ZGVtbzpkZW1vMTIz"

API Endpoints

Endpoint	Method	Description	Authentication
/api/v1/register	POST	Register new user	No
/api/v1/fund	POST	Add funds to account	Yes
/api/v1/pay	POST	Pay another user	Yes
/api/v1/bal	GET	Check account balance	Yes
/api/v1/stmt	GET	View transaction history	Yes
/api/v1/product	POST	Add new product	Yes
/api/v1/product	GET	List all products	No
/api/v1/buy	POST	Purchase a product	Yes

Prerequisites

• Java 21 or higher
• Maven 3.6 or higher

Local Development

1. Clone the repository

   git clone <repository-url>
   cd Digitalwallet

2. Build the project

   ./mvnw clean install

3. Run the application

   ./mvnw spring-boot:run

4. Access the application

   • API Base URL: http://localhost:8080/api/v1

Project Structure

src/
├── main/java/com/assignment/Digitalwallet/
│   ├── Config/              # Security and application configuration
│   ├── Controller/          # REST API controllers
│   ├── Dto/                 # Data Transfer Objects
│   ├── Exception/           # Custom exception handlers
│   ├── Model/               # JPA entities
│   ├── Repository/          # Data access layer
│   └── Service/             # Business logic layer
└── resources/
    └── application.properties

Authentication

The application uses Spring Security with HTTP Basic Authentication. After registering, use your username and password for authenticated endpoints.

Base64 Encoding Example:

echo -n "username:password" | base64

Docker Support

Build and run with Docker:

docker build -t digital-wallet .
docker run -p 8080:8080 digital-wallet

Architecture

The Digital Wallet System follows a layered architecture pattern with secure authentication, external API integration for currency conversion, and persistent data storage.

The architecture includes:

• User Authentication - Secure login and session management
• API Server - RESTful endpoints for all wallet operations
• Currency Converter API - External service for real-time currency conversion
• PostgreSQL Database - Persistent storage for users, transactions, and products
• Backend Services - Business logic for payments, products, and transactions

License

This project is developed as part of an assignment.