Clean architecture - Protecting the Domain
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The goal of architecture is to simplify the most complex parts of your logic. Any other goal should be secondary to this. The problem is that you can’t always anticipate where the complexity of your application will accumulate, especially when confronted with ever-changing requirements. The only way to keep your code simple is to gradually evolve the architecture without adding useless complexity up front, but always looking out for opportunities to break-down and refactor towards the most simple design that solves the problem. Drawing concepts from the Domain-Driven Development mindset, this talk summarizes the most important lessons learned designing and consulting many real-world projects. Along the way, you’ll hear about Value Objects and Entities, DTOs, Dependency Inversion Principle, Facades, the Onion Architecture and many pragmatic tips and tricks immediately applicable to your day-to-day work.
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Clean architecture - Protecting the Domain
- 2. 2 VictorRentea.ro a training by = Software architecture refers to the fundamental structures of a software system and the discipline of creating such structures and systems. Each structure comprises software elements, relations among them, and properties of both elements and relations.
- 3. 3 VictorRentea.ro a training by = The Stuff That's Hard to Change Later = The Art of Drawing Lines (boundaries) = The Stuff That Matters
- 5. 5 VictorRentea.ro a training by The Code - anonymous developer
- 6. Hi, I'm Victor Rentea Java Champion – drinking since 2006 Trainer – 3000+ developers / 80+ companies, since 2013 Speaker – Conferences & Meetups Hibernate Spring Java8/FP Java Performance Reactive Programming Architecture Clean Code Unit Testing Java Champion – drinking since 2006 Trainer – 3000+ developers / 80+ companies, since 2013 Speaker – Conferences & Meetups Hibernate Spring Java8/FP
- 7. $ Hibernate Spring Java8/FP Java Performance Reactive Programming Architecture Clean Code Unit Testing Masterclass Company Training Video Courses Talks & Channel Join My Communit y Blog @victorrentea VictorRentea.ro victorrentea@gmail.com
- 8. 8 VictorRentea.ro a training by Layers SUB-DOMAINS Controller Service Repository APIs order Product user customer Client
- 9. 9 VictorRentea.ro a training by Axiom 1: Logic is simpler if implemented using data structures we control
- 10. 10 VictorRentea.ro a training by Axiom 1: Logic is simpler if implemented using data structures we control Smaller: only the 5 required fields, not all 20 OOP: with helper methods inside Safer: null-safe, guarding invariants, immutable? Extract Value Objects Split Large Entities vs BC Keep DTOs out
- 11. 11 VictorRentea.ro a training by DTOs are Evil Chapter 1
- 13. 13 VictorRentea.ro a training by Exposed APIs To browsers To other systems Nanoservice called by js,ng,jsx,...
- 14. 14 VictorRentea.ro a training by Decouple API from Domain Model Delete “canBeDeletedByCurrentUser”: false To browsers “dateFormatted”: "1 Iunie 2021" DTOs are controlled by Frontend
- 15. 15 VictorRentea.ro a training by APIs To browsers DTOs are controlled by Frontend DTOs are negotiated with clients DTOs can be shared within the same Bounded Context Nanoservice =XXS microservice eg. 5 devs maintaining 20 microservices Multiple FEs/mobile: GraphQL To other systems Bounded Context A (TeamA) Bounded Context B (TeamB) 1 2 3 X
- 16. 16 VictorRentea.ro a training by Decoupling DTO Domain Model < > Price: more classes + mapping Exception: Boundary Systems = Huge Adapters without own Domain Software Ecosystem Generated DTOs: JSON: .yaml ➔ swagger-gen XML: .xsd/.wsdl ➔ xjc
- 17. 17 VictorRentea.ro a training by Auto-Generated Mappers eg. Entity DTO as long as the field names match, mapping happens automatically eg MapStruct Temptation: Keep the models in sync Entities and DTOs should will diverge
- 18. 18 VictorRentea.ro a training by domain Value Object Entity id Domain Service The code you want to protect: stays in domain module! Priceless Domain Logic Domain Objects What's specific to your app
- 19. 19 VictorRentea.ro a training by External Service domain DTO call Domain Service
- 20. 20 VictorRentea.ro a training by External Service DTO Adapter Domain Service Domain Service <dependency> domain infrastructure Goal: Keep Your Precious Domain isolated from external influences may slip in DTO
- 21. VictorRentea.ro 21 External Service DTO IAdapter Adapter implements class UserApiClient implements IUserAdapter { public User getById(id){ <external call> } } interface IUserAdapter { User getById(id); } class OrderService { @Autowired IUserAdapter adapter; ... adapter.getById(id); } express your need in a domain interface… and implement it in a lower-level module… When you need to call outside… so nothing foreign enters your domain. Domain Service Domain Service <dependency> domain infrastructure DTO
- 22. 22 VictorRentea.ro a training by calls Dependency Inversion Principle <dependency> higher-level module lower-level module "Best of OOP" - Uncle Bob Abstractions should not depend on details Low level classes are not visible (SOLID Principles) Dependency Inversion
- 23. 23 VictorRentea.ro a training by calls <dependency> higher-level module lower-level module RMI, HTTP GRPC.. FTP Queue DB DTO Dependency Inversion
- 24. 24 VictorRentea.ro a training by Stop Code Dependencies Dependency Inversion Package Dependency Checks - by static code analysis - by compiler @Test public void dependencyInversionTest() { ArchRuleDefinition .noClasses().that().resideInAPackage("..domain") .should().dependOnClassesThat().resideInAPackage("..infra") .check(new ClassFileImporter().importPackages("my.corp.app")); } testImplementation com.tngtech.archunit:archunit-junit4:0.15.0 or NDepend (C#) https://nx.dev/latest/angular/structure/monorepo-tags https://github.com/MaibornWolff/ts-arch
- 25. 25 VictorRentea.ro a training by An Agnostic Domain lets you focus on YOUR logic Agnostic Domain
- 26. 27 VictorRentea.ro a training by infrastructure EXTERNAL API Value Object Entity id Domain Service IAdapter Onion Architecture Behold, the famous Database domain Repo Dep Inv Dep Inv DTO Agnostic Domain application DTO Your Client Validation Separate Persistence Model if DB == enemy Façade Mapper Controller Adapter Spring Data IRepo
- 27. 28 VictorRentea.ro a training by 28 DTO Value Object Entity id Domain Service application Database domain DTO Onion Architecture Pragmatic Agnostic Domain EXTERNAL API Your Client Façade Mapper Controller Adapter IAdapter IRepo Dep Inv
- 28. 29 VictorRentea.ro a training by Independent of Intrusive Frameworks Testable Standalone without a DB, UI, Web Server, etc... https://blog.cleancoder.com/uncle-bob/2012/08/13/the-clean-architecture.html Independent of UI mobile, web, or desktop Independent of DB avoid PL/SQL, no vendor lock-in Independent of External APIs = external Bounded Contexts Is an ORM intrusive? Keep core logic ... Agnostic Domain aka Hexagonal aka Ports-and-Adapters aka Clean Architecture Onion Architecture
- 29. 31 VictorRentea.ro a training by Keep Domain Object design independent of persistence Decompose large flat Entities with @Embeddable Avoid useless IDs with @ElementCollection Constructor constraints are possible, hiding default one Question entity links. Aren't IDs enough? Designing Expressive and Performant Persistence Models https://www.youtube.com/watch?v=iw0tOx7Zbjc Legacy DB Schema ➔ Separate Models Mappers ➔ Pain Avoid bi-directional links
- 30. 32 VictorRentea.ro a training by Axiom 1: Logic is simpler if implemented using data structures we control Smaller: only the 5 required fields, not all 20 OOP: with helper methods inside Safer: null-safe, guarding invariants, immutable? Extract Value Objects Split Large Entities vs BC Keep DTOs out
- 31. 33 VictorRentea.ro a training by Extract Value Objects from Entities Chapter 2
- 32. 34 VictorRentea.ro a training by How many fields it has? Can you make it immutable? Tell me about that big entity ... How do you feel about moving logic inside?
- 33. 35 VictorRentea.ro a training by How many fields it has? Can you make it immutable? How do you feel about moving logic inside? Yes! (use @Embeddable for JPA) But, How to identify Value Objects? Extract Value Objects from Entities:
- 34. 36 VictorRentea.ro a training by Conceptual Whole Money {amount, currency} Changes Together LastModifiedBy/Time How to identify Value Objects? Screens InvoicingDetails Moves Together PriceComputationInput
- 35. 37 VictorRentea.ro a training by Chapter 3 The Confused Entity
- 36. 38 VictorRentea.ro a training by What's bad with Legacy Code? Old-style, -frameworks Massive Unknown Code Excessive Coupling
- 38. 40 VictorRentea.ro a training by Order Product «entity» Product 40 fields «entity» Product 15 fields «entity» Product 30 fields
- 39. 41 VictorRentea.ro a training by Order Product «entity» Product 15 fields «entity» Product 30 fields
- 40. 42 VictorRentea.ro a training by Axiom 1: Logic is simpler if implemented using data structures we control Smaller: only the 5 required fields, not all 20 OOP: with helper methods inside Safer: null-safe, guarding invariants, immutable? Extract Value Objects Split Large Entities vs BC Keep DTOs out
- 41. Axiom 1: Logic is simpler if implemented using data structures we control Clean Architecture Thank you! victorrentea@gmail.com VictorRentea.ro @victorrentea