Overview A production-grade Library Management System built with Domain-Driven Design (DDD), Clean Architecture, and Hexagonal Architecture principles. This RESTful API demonstrates enterprise-level Java development practices with a focus on maintainability, testability, and scalability. The system handles book catalog management, user/member management, borrowing operations, and includes comprehensive authentication and authorization features.
Tech Stack Java 17 with Spring Boot 3.3.3 PostgreSQL 15 with Flyway for database migrations Spring Security 6 with JWT (JJWT 0.12.6) for authentication Spring Data JPA with Hibernate 6 Lombok for boilerplate reduction TestContainers for integration testing GitHub Actions for CI/CD JaCoCo for code coverage (50% minimum threshold) Key Features Book Management: Full CRUD operations with ISBN validation (ISBN-10/13 formats), availability tracking, and copy management User Management: Role-based system with ADMIN, USER, and GUEST roles, each with different borrowing limits and durations Borrowing System: Complete borrowing workflow including book checkout, returns, due date extensions, overdue tracking, and automatic penalty calculation ($1/day) JWT Authentication: Secure HTTP-only cookie-based authentication with role-based access control Security Features: CSRF protection, XSS filtering with Content Security Policy headers, BCrypt password encryption Clean Architecture: Clear separation between Domain, Application, Infrastructure, and Interface layers with 18 single-responsibility use cases Challenges & Solutions Challenge 1: Maintaining Clean Architecture Boundaries Implementing true Clean Architecture required strict discipline in keeping domain logic free from framework dependencies. Solution: Created separate JPA entities in the infrastructure layer with mappers to convert between domain and persistence models, ensuring the domain layer remains pure.
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