Posts Tagged ‘CleanArchitecture’
[SpringIO2023] Anatomy of a Spring Boot App with Clean Architecture: Steve Pember
In a thought-provoking session at Spring I/O 2023, Steve Pember, a seasoned developer from Boston-based startup Stavi, explored the principles of Clean Architecture and their application within Spring Boot applications. Drawing from Robert Martin’s influential book, Steve demonstrated how Clean Architecture, inspired by patterns like Ports and Adapters and Hexagonal Architecture, fosters readable, flexible, and maintainable codebases. Through a reference application and practical insights, he provided a roadmap for developers to structure Spring Boot apps that remain resilient to change and scalable for large teams.
The Case for Software Architecture
Steve began by addressing the often-misunderstood role of software architecture, challenging the stereotype of architects as mere whiteboard enthusiasts. He likened software architects to their building counterparts, who design every detail from high-level structures to minute specifics. Without proper architecture, Steve warned, systems devolve into unmaintainable “big balls of mud,” slowing development and hindering competitiveness. He highlighted the benefits of well-architected systems—separation of concerns, modularity, testability, and maintainability—arguing that these guardrails enable teams to maintain velocity over time, even if they initially slow development.
Principles of Clean Architecture
Delving into Clean Architecture, Steve outlined its core concepts: SOLID principles, component design, boundaries, and dependency rules. He clarified SOLID principles, such as single responsibility (supporting one user type per class) and dependency inversion (using interfaces), as foundational to clean code. Components, he explained, should be independently developable and loosely coupled, aligning with domain-driven design or microservices. The defining feature of Clean Architecture is its layered structure, where dependencies point inward to a core of business logic, encapsulated by interfaces that shield it from external details like databases or third-party services. This ensures the core remains agnostic, enhancing flexibility and testability.
Implementing Clean Architecture in Spring Boot
Steve demonstrated how to apply Clean Architecture in Spring Boot using a reference shoe store application. He proposed a multi-module structure with three components: core (housing business logic, entities, and services), details (containing database and third-party integrations), and app (where Spring configuration and integration occur). By using interfaces for repositories and gateways, the core remains independent of external systems, allowing seamless swaps, such as replacing a PostgreSQL repository with DynamoDB. Steve emphasized minimal controllers and service classes, advocating for specific, single-responsibility services like CustomerOrderQueryService. He also highlighted the importance of integration tests, using tools like Testcontainers to validate interactions with external systems.
Treating Details as Deferrable
A key takeaway was Steve’s mantra that “everything not in core is a detail.” Databases, environments, input mechanisms, and even Spring itself should be treated as implementation details, deferrable until necessary. He cautioned against premature database schema design, urging developers to prioritize business logic over storage concerns. By encapsulating details behind interfaces, applications become adaptable to changes, such as switching databases or input methods (e.g., HTTP to Kafka). Steve’s demo showcased this flexibility, swapping a PostgreSQL order repository for DynamoDB with minimal code changes, proving the power of Clean Architecture’s plug-in approach.