Question: double validation? about domain-driven-hexagon HOT 2 CLOSED

Good point, different validation rules are a mistake, fixed it.

IMO both rules have to be similar,

• DTO validation is mostly needed for sanity checks and to prevent user input even getting past a controller if something is incorrect. It should be as strict as possible, but only for sanity checks (like checking email format) to inform a user before even getting to services (Notification pattern)
• Sanity validations in Value Objects are mostly to prevent programmer errors and for reusability. How strict it will be depends on your needs, but it at least should do basic validation.

Duplication is a downside of this approach, in most small-medium projects it probably may be an overkill. For bigger projects it's more useful since when a value is used in multiple places you don't have to do checks like if (variable...) every time in methods where this value is used, it if exists you know it is valid (better explanation here).

from domain-driven-hexagon.

Thanks for the great source-based response, as ever. Keep the good work!

from domain-driven-hexagon.