Android Clean Architecture: Understanding the Data Layer

Sean Coyle from ASOS breaks down the Data Layer in Android Clean Architecture—the unsung hero that keeps your networking, databases, and caching from bleeding into your business logic.

This deep-dive article examines how to structure the Data Layer in Android apps using Clean Architecture principles. Coyle walks through repositories, data sources, DTOs, entities, and mappers, explaining how each component maintains separation of concerns while handling everything from API calls to local caching.

Key Takeaways

• Repositories orchestrate data flow but never contain business logic or depend on other repositories
• Data Sources handle mapping, threading, and error logging before passing domain models upstream
• Use runSuspendCatching to automatically rethrow CancellationExceptions and prevent UI hangs
• Map raw exceptions to domain-specific error types at the Data Source level for consistent handling
• Aggregate data from multiple repositories in Use Cases, not in other repositories

The article reveals a common anti-pattern that creates circular dependencies between repositories and explains exactly how to fix it with Use Cases.