UPI Backend System using Java & Spring Boot

A comprehensive backend system for UPI (Unified Payment Interface) built with Java and Spring Boot.

Note: This is a simulated backend intended for learning and prototyping. Real UPI integration requires approval from NPCI/RBI.

Features

• User authentication and authorization with JWT
• Bank account management
• Virtual Payment Address (VPA) management
• Transaction processing
• Role-based access control
• API documentation with Swagger/OpenAPI

Technology Stack

• Java 17
• Spring Boot 2.7.x
• Spring Security
• Spring Data JPA
• PostgreSQL (with H2 for testing)
• JWT for authentication
• Lombok for reducing boilerplate code
• ModelMapper for DTO conversions
• Swagger/OpenAPI for API documentation

Project Structure

src/main/java/com/upi/
├── config/                  # Configuration classes
├── controller/              # REST controllers
├── dto/                     # Data Transfer Objects
│   ├── auth/                # Authentication DTOs
│   ├── bank/                # Bank account DTOs
│   ├── transaction/         # Transaction DTOs
│   └── vpa/                 # VPA DTOs
├── exception/               # Exception handling
├── model/                   # Entity classes
├── repository/              # JPA repositories
├── security/                # Security configuration
│   ├── jwt/                 # JWT utilities
│   └── services/            # Security services
├── service/                 # Service interfaces
│   └── impl/                # Service implementations
└── util/                    # Utility classes

Getting Started

Prerequisites

• Java 17 or higher
• Maven 3.6 or higher
• PostgreSQL 12 or higher

Database Setup

1. Create a PostgreSQL database named upidb:

CREATE DATABASE upidb;

2. Update the database configuration in application.properties if needed:

spring.datasource.url=jdbc:postgresql://localhost:5432/upidb
spring.datasource.username=postgres
spring.datasource.password=postgres

Building and Running

1. Clone the repository:

git clone https://github.com/Github-Saurabh0/Design-a-backend-for-upi-using-Java.git
cd Design-a-backend-for-upi-using-Java

2. Build the project:

mvn clean install

3. Run the application:

mvn spring-boot:run

The application will start on port 8080 by default.

API Documentation

Swagger UI is available at: http://localhost:8080/swagger-ui.html

API docs are available at: http://localhost:8080/api-docs

Authentication

Register a new user

POST /api/auth/signup

Request body:

{
  "username": "johndoe",
  "firstName": "John",
  "lastName": "Doe",
  "email": "[email protected]",
  "phone": "1234567890",
  "password": "password123",
  "roles": ["user"]
}

Login

POST /api/auth/signin

Request body:

{
  "username": "johndoe",
  "password": "password123"
}

Response:

{
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
  "id": 1,
  "username": "johndoe",
  "email": "[email protected]",
  "phone": "1234567890",
  "roles": ["ROLE_USER"]
}

Author

Saurabh Kushwaha
🔗 Portfolio
📧 [email protected]
🔗 LinkedIn
🔗 Instagram Dev Page

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License

This project is licensed under the MIT License.

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