Campus ID–Based Vending Payment System

A computer science project that simulates a school-issued ID card payment system for campus vending machines using mock currency. Each student automatically receives a weekly allowance every Monday, which can only be spent on campus by swiping their student ID.

This project is designed as a realistic backend systems simulation and does not involve real money or financial institutions.

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Problem Statement

Many college campuses have vending machines that claim to accept student ID cards but don't actually work with the campus payment system. This project provides a complete backend solution that could enable this functionality, demonstrating how ID card payments could be securely implemented across campus vending machines.

Project Overview

Many universities allow students to use their ID cards to purchase items on campus. This project recreates that environment by implementing:

• Student ID–linked accounts
• Vending machine purchase validation
• Secure transaction tracking using mock campus currency

The system is fully testable without access to real vending machines or physical ID hardware.

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Setup and Run Instructions ****** READ TO RUN PROGRAM

• Download and install Java JDK 8+ and MySQL Server 8.0+ from their official websites (remember your MySQL root password during installation)
• Download MySQL Connector/J (JDBC Driver) from mysql.com/downloads/connector/j/ and save it somewhere accessible
• Clone this repository: git clone https://github.com/zacton19/campus-vending-system.git
• Open MySQL Command Line or MySQL Workbench and connect to your MySQL server with your root password
• Run the database schema: source path/to/schema.sql (replace path/to/ with actual file path, or in MySQL Workbench: File → Open SQL Script → select schema.sql → click lightning bolt)
• Run the seed data: source path/to/seed.sql (this creates 100 students, 15 vending machines, 50 products, and fully stocked inventory)
• Open the project folder in IntelliJ IDEA (File → Open → select the cloned folder)
• Add the MySQL Connector JAR to your project: File → Project Structure (Ctrl+Alt+Shift+S) → Libraries → + → Java → navigate to and select the mysql-connector-j-8.x.x.jar file you downloaded → click OK
• Open DatabaseManager.java and update lines 6-7 with your MySQL credentials: change "root" if you used a different username, and replace "your_password" with your actual MySQL password
• Start the server first: Run PaymentServer.java (right-click the file → Run 'PaymentServer.main()') - you should see "=== Campus Payment Server Starting ===" and "Listening on port 8888" - leave this running
• Then start the client: Run VendingMachineClient.java in a separate run window (right-click → Run 'VendingMachineClient.main()') while the server is still running
• Select a vending machine location (1-15) when prompted
• Login with any Student ID from S00001 to S00100 (all test accounts use PIN: 1234)
• Browse products, make purchases, switch between different vending machines, and watch your balance update in real-time across all locations
• The server handles all authentication, transactions, and database operations securely with password hashing and SQL injection prevention
• Troubleshooting: If you get "Cannot connect to payment server" - make sure PaymentServer is running first and port 8888 isn't blocked
• Troubleshooting: If you get "Authentication failed" - verify you're using Student ID format S00001-S00100 with PIN 1234
• Troubleshooting: If you get "No products available" - make sure you ran both schema.sql and seed.sql files
• Troubleshooting: If MySQL connection fails - verify MySQL Server is running (check Windows Services for "MySQL80") and credentials in DatabaseManager.java are correct

Core Features

Student Accounts

• Unique student ID associated with each account
• Secure balance tracking
• Persistent transaction history

ID Card Swipe System

• Simulated ID swipe authentication
• Balance verification before purchase
• Instant deduction upon successful transaction

Vending Machine Integration

• Each vending machine has:
  • A unique machine ID
  • Item inventory
  • Configurable prices
• Prevents purchases when funds are insufficient
• Logs all purchase activity

Weekly Allowance Automation

• Every Monday, all active student accounts are credited with a fixed allowance
• Allowance amount is configurable
• Implemented using a scheduled background task

Safety Constraints

• Uses mock, school-specific currency only
• Currency is restricted to campus use
• No real money, banking APIs, or payment processors involved

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Key Technical Features

• Client-Server Architecture: Distributed system with TCP socket communication between vending machines and central payment server
• Secure Authentication: PBKDF2 password hashing with SHA-256 and unique salts per user (10,000 iterations)
• ACID Transactions: Database transactions ensure balance updates and inventory changes happen atomically
• Multi-threaded Server: Handles multiple vending machines simultaneously
• SQL Injection Prevention: All database queries use prepared statements
• Real-time Balance Updates: Student balances sync across all 15 campus locations instantly

System Architecture

Student ID Card ↓ Vending Machine ↓ Campus Payment API ↓ Student Account Database

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Technology Stack

• Backend: Java
• Database: MySQL with JDBC
• Architecture: Client-Server model with TCP sockets
• Security: PBKDF2WithHmacSHA256 password hashing
• Networking: Java Socket API for client-server communication
• Data Transfer: Java Object Serialization for request/response protocol

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How It Works

This is a fully functional system with:

• Real client-server communication over TCP sockets
• Actual MySQL database with persistent storage
• Working authentication and transaction processing
• Live balance updates across multiple machines

While it doesn't connect to physical vending machines or real card readers, all the backend logic, security, and data handling are production-ready implementations that could be integrated with real hardware.

Learning Objectives

This project demonstrates:

• Client-Server Architecture: Multi-threaded server handling concurrent connections
• Network Programming: TCP socket communication and custom protocol design
• Database Design: Normalized schema with proper foreign keys and constraints
• Security: Password hashing, salt generation, and SQL injection prevention
• Transaction Management: ACID-compliant financial transactions
• Object-Oriented Design: DAO pattern, DTOs, and separation of concerns
• Concurrency: Thread-safe transaction processing with synchronization

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This project uses mock campus currency only. It does not process real money, connect to financial institutions, or integrate with actual vending machines. This system is intended solely for academic, educational, and portfolio purposes.

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Future Enhancements

• Administrative dashboard for managing students and machines
• Fraud prevention (duplicate swipe detection)
• Spending analytics
• Mobile app integration
• Hardware abstraction for RFID/NFC readers

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Contributions

This is an open project. Suggestions, issues, and pull requests are welcome.