Repository No Business Logic

Goal

Repositories must contain no business logic. A repository is a persistence gateway — it persists and retrieves domain entities exactly as instructed by its caller.

A repository's responsibility is limited to:

• translating between domain types and persistence representations
• executing persistence operations — create, update, find, delete
• mapping query parameters to persistence queries

A repository must not:

• validate business rules or enforce domain invariants
• make domain decisions based on the data it reads or writes
• transform domain state — that is the entity's or domain service's responsibility
• filter or exclude results based on business criteria not expressed by the caller
• trigger side effects that represent business behavior