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ADR-003: Rich Domain Model Over Anemic Domain Model

  • Date: 2026-08-01
  • Status: Accepted
  • Phase: Phase 2A

Context & Problem Statement

Anemic domain models treat JPA entities as simple data bags with getters and setters, scattering business invariants (such as non-negative balance checks and debit rules) across multiple service classes.

Considered Options

  1. Anemic Domain Model: Entities hold only state; services perform all business logic and validations.
  2. Rich Domain Model: Entities encapsulate state alongside domain behaviors and invariant checks (debit(), credit()).

Decision Outcome

Chosen Option: Rich Domain Model

Rationale

Rich domain entities encapsulate domain invariants directly within entity boundaries (User.debit(), User.credit()), preventing invalid domain state transitions (e.g. negative balances or invalid debit amounts) regardless of caller invocation path.

Consequences

  • Positive: High cohesion, self-validating entities, reusable business logic across multiple services.
  • Negative / Trade-offs: Entities must remain decoupled from infrastructure concerns (repositories, external APIs).
  • Risks & Mitigations: Keep entity methods focused strictly on state invariants; delegate orchestration to domain services.