Object-Oriented Design Review (OOP Design Review)

A skill that diagnoses and improves design smells using the roles, responsibilities, and collaboration and responsibility-driven design of Cho Young-ho's "Object" and "The Reality and Misconception of Object Orientation", together with SOLID, GRASP, and the cohesion/coupling principles. For grounding facts, see this skill's reference/kb/ (SOLID, GRASP, cohesion/coupling, encapsulation/invariants, composition vs. inheritance, the Law of Demeter); for the principles, see reference/principles.md. The index is reference/kb/INDEX.md (if you can't find the path, search with Glob).

Review order (proceed exactly like this)

1. Diagnose responsibility placement — Is the logic piled up in a service far away from the data (the entity) (anemic domain)?
2. Tell, Don't Ask — Code that calls getX() and then decides externally and setY()s → delegate to the object that holds that data.
3. Encapsulation — Is mutable internal state (collections/state) exposed as-is → read-only + mutating methods.
4. Dependency direction — Does a stable abstraction depend on an unstable concrete (DIP violation) → invert via an interface (port).
5. Persistence leakage — The domain depends directly on EntityManager/@Repository, the entity is exposed all the way to the API → separate them.
6. Report — Before/After + application steps. Don't break persistence invariants or transaction semantics (separate out behavior changes).

Design smell → prescription

Rules

• Decide responsibility by "who is the most natural to bear it" (behavior first, not data).
• When turning something into an entity method, make the entity uphold the persistence invariants (identifier/association consistency).
• Changing transaction boundaries or association fetching is a behavior impact → separate it from pure refactoring and mark it.

Example (anemic domain → rich domain)

// Before — the service pulls out entity data to decide/assemble (Anemic + Ask)
if (order.getStatus() == OPEN && order.getItems().isNotEmpty()) order.setStatus(CANCELLED)
// After — the entity performs the responsibility with its own invariants (Tell, Don't Ask)
order.cancel()   // validates state/conditions internally