Library is a Domain-Driven Design reference implementation that demonstrates strategic analysis and tactical patterns applied to a real-world library management domain.
The project addresses the challenge of bridging the gap between domain modeling and code implementation. It tackles a concrete problem space: managing patron holds, book checkouts, and library inventory with complex business rules around patron types, hold durations, and overdue policies. The approach uses Domain-Driven Design techniques including event storming, user story mapping, and behavior-driven development to translate business requirements into code. The implementation emphasizes aggregates as consistency boundaries, event-based state changes, and explicit modeling of domain concepts rather than generic CRUD operations.
This codebase is suited for teams learning Domain-Driven Design or evaluating architectural approaches for complex domains. It works best as a reference for understanding how to structure a Spring-based application around domain logic rather than database schemas, and how to maintain alignment between business language and code. The project deliberately avoids using an ORM, instead managing data access explicitly to keep domain logic separate from persistence concerns. It uses ArchUnit to enforce architectural constraints programmatically, helping prevent the architecture-code gap that emerges as projects grow. The functional programming style through the Vavr library demonstrates an alternative to traditional object-oriented domain modeling.
The project shows consistent attention to maintaining code-domain alignment through architectural testing and explicit separation of concerns. Development activity reflects a focus on demonstrating patterns rather than building production features, with comprehensive documentation of design decisions and trade-offs embedded throughout the structure.
