Movie Rental System Refactoring Project

This is a Java implementation of a movie rental system for generating customer rental statements. This project demonstrates how to refactor existing code to improve code quality and maintainability.

Refactoring Report

Preliminary Work

1. Maven Project Structure Conversion

   • Converted the project to Maven structure for automated dependency management
   • Established foundation for CI/CD pipelines and Docker deployment
   • Standardized project structure for better developer understanding and collaboration

2. Continuous Integration Setup

   • Configured CI workflow on GitHub to ensure each commit passes tests
   • Set up failure notification mechanisms for quick issue discovery
   • Created a safety net for the refactoring process to prevent regression issues

3. Test Coverage Enhancement

   • Added comprehensive test cases, including basic functionality and boundary conditions
   • Ensured existing functionality has clear validation criteria
   • Used tests to confirm actual system behavior and guide refactoring decisions

Refactoring Implementation Process

1. Domain Model Clarification

   • Identified relationships between core models: Customer, MovieRental, and Movie
   • Defined clear responsibility boundaries for each class according to the Single Responsibility Principle
   • Redesigned data flow paths to avoid unnecessary data transformations

2. Magic Constant Elimination

   • Replaced string constants with strongly-typed MovieType enumeration to enhance type safety
   • Improved code readability and maintainability while reducing potential errors
   • Provided better IDE support for code completion and checking

3. Evolution of Calculation Logic Refactoring

   • Initial approach: Moved calculation logic to MovieRental class since calculations only depend on movie type and rental days
   • Further consideration: As movie types and calculation rules increase, MovieRental would take on too many responsibilities
   • Issue insight: This would bloat the MovieRental data class, making unit testing difficult
   • Final decision: Applied Strategy pattern to separate calculation logic, maintaining the purity of data models

4. Strategy Pattern Implementation

   • Abstracted pricing and points calculation logic for different movie types into strategy interfaces
   • Implemented a strategy factory to manage different calculation strategy implementations
   • Made the system more easily extensible for new movie types without modifying core business logic

5. Core Business Logic Optimization

   • Refactored the statement method in RentalInfo class to clearly separate data retrieval and presentation logic
   • Removed unnecessary data assembly code, directly obtaining required information from the Customer model
   • Optimized output format to improve statement readability and professionalism

6. Project Layer Optimization

   • Naturally formed clearer project layering through the application of the Strategy pattern
   • Identified Customer, Movie, and MovieRental as pure data models, placing them in the model package
   • Reorganized code into three layers: model, service, and strategy based on responsibilities
   • Established clear dependency relationships and call directions

Project Structure

src/
├── main/java/movierental/
│   ├── model/             # Data model classes
│   │   ├── Customer.java
│   │   ├── Movie.java
│   │   ├── MovieRental.java
│   │   └── MovieType.java
│   ├── service/           # Service layer
│   │   └── RentalInfo.java
│   └── strategy/          # Strategy pattern implementation
│       ├── RentalStrategy.java
│       ├── RegularMovieStrategy.java
│       ├── NewReleaseMovieStrategy.java
│       ├── ChildrenMovieStrategy.java
│       └── RentalStrategyFactory.java
└── test/java/movierental/  # Test classes
    └── RentalInfoTest.java

How to Run

Prerequisites

• Java 21 or higher
• Maven 3.6.0 or higher

Running Tests

mvn test

Tech Stack

• Java 21
• JUnit 5
• Maven
• GitHub Actions (CI/CD)