RepositoryPattern

The RepositoryPattern is a software design pattern that mediates between the domain and data mapping layers, providing a collection-like interface for accessing domain objects. Its intent is to decouple business logic from data access concerns and to centralize data querying and persistence.

A repository exposes common data operations such as add, remove, update, and retrieve methods, including getById, getAll, and find by criteria. Concrete repositories target specific data stores or ORMs, and can implement asynchronous or synchronous variants. In many designs, a Unit of Work coordinates transactions across repositories to ensure consistency.

Patterns within repositories include a generic repository that provides basic CRUD operations for any entity type and specialized repositories that implement domain-specific queries. Advantages include improved separation of concerns, easier testing and mocking, and the ability to swap data sources with minimal impact on domain logic.

Criticisms focus on potential over-abstraction, particularly when using feature-rich ORMs that already provide rich querying capabilities; repositories can become thin wrappers or encourage an anemic domain model. The pattern is commonly associated with enterprise application architecture discussions and was popularized in Martin Fowler's Patterns of Enterprise Application Architecture, where it is described as a means to separate concerns, though its use predates the book.

In practice, the pattern remains widely used in layered architectures and domain-driven design, especially where clear boundaries between domain logic and data access are desired.