How to handle Validation in Clean Architecture?
Updated Apr 28, 2026
Short answer
Validation is split into three levels: Input Validation (Adapters), Business Logic Validation (Entities), and Use Case Validation.
Deep explanation
- Input Validation: Ensures the format is correct (e.g., email string looks like an email). Done in the Controller/Adapter. 2. Use Case Validation: Checks if the action can be performed in the current state. 3. Entity Validation: Core rules (e.g., 'price cannot be negative').
Real-world example
A registration form: UI checks for non-empty fields; Use Case checks if email is already taken; Entity checks if the password meets security rules.
Common mistakes
- Doing database checks (like 'is email unique') inside a Domain Entity.
Follow-up questions
- Should we use libraries like Joi or Zod in the Entity layer?