Java User Manager

A comprehensive Java-based backend system for managing user authentication, product licensing, and session management. Designed as a secure, scalable solution for software distribution and user access control.

User Manager is a complete user management server that handles user registration, authentication, license key distribution, product downloads, and administrative functions. It provides a RESTful HTTP API for client applications and includes advanced features like hardware ID (HWID) binding, ban management, session tracking, and changelog management.

This project was created at the request of a friend who needed a management system for his users. The system was designed to use JSON files for data handling, as the client was unfamiliar with database systems and preferred a simpler, file-based approach that could be manually inspected and edited when needed.

Given that development occurred in my free time, the system was deployed to production incrementally—long before all planned features were complete. This practical constraint influenced several design decisions: the JSON-based storage allows for direct file manipulation when administrative features weren't yet implemented, and the modular architecture enables gradual feature additions without disrupting the running system.

As this is the only project in my portfolio that has been deployed in a real-world production environment, comprehensive tests were added to ensure reliability and correctness in active use. The system has been successfully serving real users and handling actual license distribution since deployment.

• User Registration & Authentication: Secure user account creation with BCrypt password hashing
• Hardware ID Binding: Lock user accounts to specific hardware for enhanced security
• Session Management: Automatic session creation with configurable expiration times
• User Data Persistence: JSON-based storage system for reliable user data management

• Key Generation: Create license keys in bulk for product distribution
• Product Association: Link keys to specific products with custom durations
• Key Redemption: Users can redeem keys to unlock product access
• Key Management: Track key status (redeemed/available) and redemption history

• Product Catalog: Manage multiple products with associated files
• Secure Downloads: Authenticated product file downloads
• Product Purchases: Track user purchases and access permissions

• Ban System: Ban users by username, HWID, or IP address with reason tracking
• Admin API: Protected administrative endpoints with API key authentication
• Session Validation: Automatic session validation and cleanup
• Request Authentication: Multi-level security with API keys and session tokens

• Changelog System: Version tracking and update logs for products
• Config Manager: User-specific configuration management
• Activity Logging: Comprehensive logging of all user actions
• Ban Image Storage: Save evidence images for ban enforcement

Network Layer (de.lukas.eternalUserManager.network)

• Server: HTTP server handling all client requests on configurable port
• RequestHandler: Abstract base class for all API endpoints with authentication
• AdminRequestHandler: Extended handler for admin-only operations
• Request Implementations: 20+ specialized request handlers for different operations

Available Endpoints:

• login, register, redeemKey - User operations
• showProducts, download - Product access
• banUser, unbanUser, resetHWID - Admin operations
• createKeys, getKeys, deleteKey - License management
• getUsers, getActiveSessions, getProducts - Admin queries

Logic Layer (de.lukas.eternalUserManager.logic)

• UserManager: Complete user lifecycle management with password hashing
• SessionManager: Time-based session tracking with automatic expiration
• KeyManager: License key generation, validation, and redemption
• ProductManager: Product CRUD operations and access control
• BanManager: Ban list management with multi-criteria blocking
• LogManager: Changelog and update tracking system
• ConfigManager: User-specific configuration storage

Data Layer (de.lukas.eternalUserManager.data)

• DataManager: Central data access point for file operations
• IDataStorage: Storage abstraction interface
• DefaultDataStorage: File-based storage implementation
• MountedDataStorage: Virtual directory mounting for organized storage
• BufferedDataStorage: Optional caching layer for performance
• JsonDataBundle: JSON serialization/deserialization utilities

Utility Components (de.lukas.eternalUserManager.utils)

• BCryptHash: Secure password hashing with BCrypt
• JSON/JSONParser: Custom JSON handling for data serialization
• BiHashMap/BiMap: Bidirectional map implementations for efficient lookups
• Logger: Centralized logging system
• Result: Type-safe result wrapper for error handling
• TimeHelper: Time and duration utilities

src/
├── de/lukas/eternalUserManager/
│   ├── Main.java                    # Application entry point
│   ├── data/                        # Data persistence layer
│   │   ├── DataManager.java         # Central data operations
│   │   ├── IDataStorage.java        # Storage interface
│   │   ├── DefaultDataStorage.java  # File system storage
│   │   ├── MountedDataStorage.java  # Path abstraction
│   │   ├── BufferedDataStorage.java # Caching layer
│   │   └── JsonDataBundle.java      # JSON utilities
│   ├── logic/                       # Business logic
│   │   ├── Config.java              # Server configuration
│   │   ├── banList/                 # Ban management
│   │   ├── changelog/               # Version logging
│   │   ├── config/                  # User configs
│   │   ├── key/                     # License keys
│   │   ├── product/                 # Product management
│   │   ├── session/                 # Session tracking
│   │   └── user/                    # User management
│   ├── network/                     # HTTP server & API
│   │   ├── Server.java              # Main HTTP server
│   │   ├── RequestHandler.java      # Base request handler
│   │   ├── AdminRequestHandler.java # Admin operations
│   │   ├── requests/                # Public API endpoints
│   │   └── server/                  # HTTP utilities
│   └── utils/                       # Helper utilities
│       ├── BCrypthHash.java         # Password security
│       ├── BiHashMap.java           # Bidirectional maps
│       ├── JSON.java                # JSON handling
│       ├── Logger.java              # Logging system
│       └── Result.java              # Error handling
└── META-INF/
    └── MANIFEST.MF

• Facade Pattern: Managers provide simplified interfaces to complex subsystems
• Strategy Pattern: Pluggable storage and hashing implementations
• Abstract Factory: RequestHandler creation and routing
• Singleton Pattern: Logger and configuration instances
• Repository Pattern: Manager classes abstract data access

• BCrypt password hashing with automatic salt generation
• Hardware ID binding prevents account sharing
• Session-based authentication with automatic expiration
• Multi-level API key authentication (user/admin)
• IP and HWID tracking for ban enforcement
• Secure file storage with path validation consistency

This system is designed for:

• Software Licensing: Distribute and manage software licenses
• Game Server Authentication: Player account management
• SaaS Product Access: Control access to cloud services
• Digital Product Distribution: Sell and deliver digital products
• Beta Testing Management: Control access to pre-release software

Unlike other projects in my portfolio, this system includes a comprehensive test suite due to its production deployment. Tests are located in the tests/ directory and cover critical system functionality to ensure reliability in real-world usage.

The testing approach focuses on:

• User authentication and session management
• License key generation and redemption
• Data persistence and integrity
• Security features and access control

These tests have been essential in maintaining system stability while adding new features incrementally during active production use.

This project is a personal/educational project.

Lukas