📚 Library Management System (Java)

A modular, extensible Library Management System implemented in Java, designed with object-oriented best practices and multiple design patterns.
The system supports library operations such as user management, work cataloging, borrowing/returning, notifications, rule enforcement, and advanced searching, all through a clean separation between core logic and user interface layers.

✨ Key Features

• 📖 Manage different types of works (Books, DVDs, etc.)
• 👤 User registration, behavior tracking, fines, and notifications
• 🔄 Borrowing and returning workflows with rule validation
• 🔍 Advanced search using the Visitor pattern
• 🔔 Event-driven notifications for availability and requests
• 🧱 Clean separation between Application, Core Domain, and UI Library
• 🧪 Robust exception handling across all layers
• 🧩 Highly extensible architecture

🏗️ Architecture Overview

The project follows a layered architecture:

• Core: bci-core/
  Contém as classes de domínio principais da aplicação.

• Interaction: bci-app/
  Contém as classes responsáveis pela interação com o utilizador.

• UML diagrams: uml/
  Contém os diagramas UML da primeira entrega.

🧠 Design Patterns Used

🧭 Visitor Pattern

• Used for advanced search functionality
• Decouples search logic from domain entities
  (SearchVisitor, SearchFilterVisitor)

🔔 Observer Pattern

• Used in the notification subsystem
• Enables event-driven updates
  (NotificationService, NotificationListener)

🧠 Strategy Pattern

• Used for user behavior management
• Dynamic behavior switching
  (NormalBehaviour, AbidingBehaviour, WrongfulBehaviour)

🏗️ Command Pattern

• Used extensively in the application layer
• Each user action is encapsulated as a command
  (DoRegisterUser, DoRequestWork, etc.)

🧩 Layered Architecture

• UI is fully decoupled from business logic
• Core logic is reusable and UI-agnostic

📦 Domain Model Highlights (bci-core)

Works

• Abstract Work class
• Concrete implementations:
  • Book
  • DVD
• Associated entities:
  • Creator
  • Category

Users

• User entity with dynamic behavior
• Borrowing requests via Request
• Fine management and notifications

Rules Engine

Borrowing rules enforced via:

• Rule interface
• Concrete implementations:
  • NoDuplicateRequestRule
  • LimitRequestRule
  • PriceLimitRule
  • NotSuspendedRule
  • NoReferenceWorkRule

⚠️ Exception Handling

The system uses domain-specific exceptions to ensure robustness and clarity:

• UserUnknownException
• WorkUnknownException
• RuleNotMetException
• BorrowingRuleFailedException
• UnavailableFileException

This approach guarantees:

• Clear error propagation
• Strong domain boundaries
• UI-friendly error handling

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🛠️ Build & Run

Requirements

• Java 11+
• make

ClASSPATH

Before running the program, you need to configure the CLASSPATH to include the po-uilib.jar library, which is used for the text-based interface.

Em Linux/MacOS:
export CLASSPATH=.:po-uilib/po-uilib.jar

Em Windows (PowerShell):
set CLASSPATH=.;po-uilib\po-uilib.jar

Build

make
## Compilação e Execução

The compilation of the entire project (including the po-uilib library) is done automatically through the main Makefile.

```bash
make

Se quiseres definir esta configuração permanentemente, adiciona o comando ao teu ficheiro de inicialização (.bashrc, .zshrc, etc.).