Patterns, Principles, and Practices of Domain-Driven Design

21 Repositories

WHAT’S IN THIS CHAPTER?

• The role and responsibilities of the repository pattern
• The misunderstandings of the repository pattern
• The difference between a domain model and a persistence model
• Strategies for persisting your domain model based on the capabilities of your persistence framework

Wrox.com Code Downloads for This Chapter

The wrox.com code downloads for this chapter are found at www.wrox.com/go/domaindrivendesign on the Download Code tab. The code is in the Chapter 21 download and individually named according to the names throughout the chapter.

How do you create, persist, and retrieve domain objects while maintaining a domain model that is not distracted by technical concerns? For domain objects that need to live beyond in- memory use and be retrieved later, a mapping to a persistence store is required. In order to avoid blurring the lines of responsibility between domain logic and infrastructure code, repositories can be employed. Repositories ensure that persistence ignorance is retained by storing domain aggregates behind a collection façade disguising the true underlying infrastructural mechanism. Repositories ensure technical complexities are kept out of the domain model.

Repositories

A repository is used to manage aggregate persistence and retrieval while ensuring that there is a separation between the domain model and the data model. It mediates between these two models by using a collection façade that hides the complexities of the underlying ...