Evolving a Clean, Pragmatic Architecture at JBCNConf 2019
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Are you in a mood for a brainstorm? Join this critical review of the major decisions taken in a typical enterprise application architecture and learn to balance pragmatism with your design goals. Find out how to do just-in-time design to keep as much use-cases as simple as possible. The core purpose of this presentation is to learn to strike a **balance between pragmatism and maintainability** in your design. Without continuous refactoring, a simple design will inevitably degenerate into a Big Ball of Mud, under the assault of the new features and bugfixes. On the other hand, very highly-factored code can burden the take-off of the development and end up freezing the mindset in some rigid 'a-priori' design. The end goal of this talk is to challenge you to rethink critically the architecture of your own systems, and seek ways to simplify it to match your actual needs, with a pragmatic mindset. "Architecture is the art of postponing decisions", said Uncle Bob. This talk takes this idea further and explains an optimal mindset about designing enterprise applications: Evolving (Continuously Refactoring) a Pragmatic (Simple), Clean (aka Onion) Architecture, aiming to provide Developer Safety™️ and Comfort™️. It’s the philosophy that Victor distilled over the past 5 years, designing and implementing 9 applications as IBM Lead Architect, and delivering trainings and advises to many other companies. You’ll learn how to break data into pieces (Fit Entities, Value Objects, Data Transfer Objects), how to keep the logic simple (Facades, Domain Services, logic extraction patterns, Mappers, AOP), layering to enforce boundaries (keeping DTOs out of your logic, Dependency Inversion Principle), and many more, all in a dynamic, interactive and extremely entertaining session.
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Evolving a Clean, Pragmatic Architecture at JBCNConf 2019
- 2. When something is painful but you can't avoid doing it… postpone it
- 3. When something is painful but you can't avoid doing it… delegate it
- 4. When something is painful but you can't avoid doing it… Do It More Often! "Bring The Pain Forward!"
- 5. Continuous Integration Pair Programming Continuous Refactoring TDD eXtreme Programming "Bring The Pain Forward!"
- 8. Victor Rentea Clean Code Evangelist VictorRentea.ro 30+ talks, 12 meetups .NET Lead Architect Tech Team Lead and Consultant Software Craftsman XP: Pair Programming, Refactoring, TDD Java Champion
- 9. VictorRentea.ro @victorrentea victor.rentea@gmail.com Independent Technical Trainer & Coach HibernateSpring Java 8 Architecture, DDDDesign Patterns Clean Code Unit Testing, TDD Java Performance and much more…Scala 180+ days1300 devs6 years VictorRentea.rovictor.rentea@gmail.com 30 companies Posting daily on
- 13. 28 The most important principle in programming?
- 14. 29 Single Responsibility Principle EmployeeManager -read/persist -compute pay-roll -generate PDF report -manage projects vs
- 15. 30 Coupling vs
- 17. 32 Keep It Short & Simple Premature encapsulation is the root of all evilOverengineering – Adam Bien
- 18. 33 Keep It Short & Simple Premature encapsulation is the root of all evilOverengineering Simpler code Developer Happiness
- 19. 34 Invisible Magic to reduce effort and risk Protect the Developers ... Avoid building an intrusive Custom Framework (bugs to learn) Developer Comfort
- 20. 35 Request/Thread Scope @Autowired private MyRequestContext requestContext; ... { entity.setModifiedBy(requestContext.getCurrentUser()); } @Component @Scope(value = "request", proxyMode = TARGET_CLASS) class MyRequestContext { ... } Request Metadata
- 21. Fear Kills Creativity Simplify Unit Testing - Strong regression defense Protect the Developers 36 Developer Safety
- 22. Always Think Regular Brainstorming 37 Continuous Refactoring There are NO boring tasks automate them
- 23. 38
- 24. 41 No? Then Keep Struggling for a Can you predict the future ? What features will evolve super-complex in time? Simple Design At all times!
- 25. 42 - Kent Beck https://martinfowler.com/bliki/BeckDesignRules.html 2. Reveals Intention 3. No Duplication 4. Fewest Elements 1. Passes the Tests Rules of Simple Design
- 26. 43 A Simple Architecture that Evolves to Match the Growing Complexity This talk is about…
- 27. 44 Core Principles Modeling Data Organizing Logic The Onion Architecture Tests. Fear. Agenda VictorRentea.ro
- 28. You control them! Entities = your persistent data 45 Entity They simplify your logic
- 29. 46 Put small bits of highly reusable domain logic in your Domain Entities public class Customer { [...] public String getFullName() { return firstName + " " + lastName; } public void activate(User user) { if (status != Status.DRAFT) { throw new IllegalStateException(); } status = Status.ACTIVE; activatedBy = user; activatedDate = new Date(); } public boolean isActive() { return status == Status.ACTIVE; } public boolean canPlaceOrders() { return status == Status.ACTIVE && !isBann }
- 30. 47 activatedBy = user; activatedDate = new Date(); } public boolean isActive() { return status == Status.ACTIVE; } public boolean canPlaceOrders() { return status == Status.ACTIVE && !isBann } public void addAddress(Address address) { address.setCustomer(this); addresses.add(address); } public List<Address> getAddresses() { return Collections.unmodifiableList( addresses); } } public String toExportString() { return String.format("%s;%s;%d", firstName, lastName, isActive()?1:0); } BlOAt dAnGeR Fit Put small bits of highly reusable domain logic in your Domain Entities
- 31. Entityid 48 Small Immutable Lombok? No persistent ID unlike an Entity Equal by value of all fields Embeddable In larger entities Value Object: a grouping of domain data VO public class Money { private final Currency currency; private final BigDecimal amount; public Money(Currency currency, BigDecimal amount) { this.currency = currency; this.amount = amount; } public Currency getCurrency() { return currency; } public BigDecimal getAmount() { return amount; } public boolean equals(Object other) { ... } } validate();
- 32. Then, you start exposing data to UI (SPA, WS, JSF, desktop) UI has different goals They want data structures to match their screens. Never expose your Entities in your API 49 isDeletable: true (to show the Delete button)
- 33. I like dumb DTOs (you'll see soon why) public fields ?! ! !.. VOEntityid Logic public class CustomerDto { private String fullName; private String phoneNumber; private Date birthDate; public final String getFullName return fullName; } public final void setFullName(S this.fullName = fullName; } public final String getPhoneNum return phoneNumber; } public final void setPhoneNumbe this.phoneNumber = phoneNumbe } public final Date getBirthDate( return birthDate; } public final void setBirthDate( this.birthDate = birthDate; } } 50 Form/Request View/Response DTO SearchCriteria/SearchResult Data Transfer Objects DTO Instead, expose in your API public class CustomerDto { public String fullName; public String phoneNumber; public Date birthDate; } dto.fullName = customer.getFullName();
- 34. 51 Core Principles Modeling Data Organizing Logic The Onion Architecture Tests. Fear. Agenda
- 35. 52 Complex Conversion? Extract Mappers VOEntityid DTO Mapper Logic API Domain CustomerDto dto = new CustomerDto(); dto.fullName = customer.getFullName(); dto.birthDate = customer.getBirthDate(); dto.phoneNumber = customer.getPhoneNumber(); CustomerDto dto = new CustomerDto(customer);
- 36. 63 Start implementing all domain logic in a Facade Mapper VOEntityid DTO Facade Facade Domain Service Domain Service Domain Services This approach is detailed in Java EE Patterns - Rethinking Best Practices, by Adam Bien Then extract logic into -To hide complexity: SRP -For Reuse: DRY ▪ (across Facades or Services) ≈ Application Service [DDD]
- 37. 65 Keep DTOs out! (parameters and return types) Mapper VOEntityid DTO Facade Facade Domain Service Domain Service Domain Services speak your Domain Model Convert them to your Domain Objects ASAP DTOs are fragile (under enemy control) * I like them dumb (no methods)
- 38. Fç Validate Data Façade Convert Data Implement Logic Aspects - Transactions - Logging - Exception Handling* - Access Control* 66 Facade Roles DTO Validator Mapper Domain Service VOEntityid
- 39. 67 What do you mean ? When a class gets too big (>~200 lines?) ➔ break it Extract when it Grows How? Find a good class name to summarize some of its methods If I find a good name, I extract? That’s it? Exactly! Piece a cake! A Good Name He-he!☺ “There are only two things hard in programming: Cache Invalidation and Naming Things”
- 40. 68 SRP applied to reduce complexity
- 41. 69 CustomerFacade saveCustomer() getCustomer() searchCustomer() saveCustomerPreferences() getCustomerPreferences() validateAddress() resetPassword() checkPassworStrength() CustomerPreferecesFacade saveCustomerPreferences() getCustomerPreferences() validateAddress() resetPassword() checkPassworStrength() CustomerFacade saveCustomer() getCustomer() searchCustomer() Controller Extract when it Grows at the same level of abstraction Horizontal Splitting > 300 lines
- 42. AlertService CompositeOrder Service 70 Separation by Layers of Abstraction OrderService DeliveryService Extract when it Grows Vertical Extraction more abstract, more higher-level
- 43. 72 Duplication Pair Programming Imposed validate in JS/TS and in Java Rush/Lazy Inadvertent you forget and implement it again Inter-developer you didn't knew that was already implemented (Δt=5-10s) bus factor =2
- 45. 74
- 46. Developer Comfort is essential for Emerging Architectures
- 47. 77
- 48. 78 Core Principles Modeling Data Organizing Logic The Onion Architecture Tests. Fear. Agenda VictorRentea.ro
- 49. 79 VOEntityid Domain Service Domain Service What code would you protect? Put it in the domain module Priceless Domain Logic Domain Objects domain
- 52. 82 External Service DTO Adapter Domain Service Domain Service <dependency>domain infrastructure A huge Adapter® Pattern - Hide their ugly API - Handle their Exceptions - Decouple their DTOs your Entities - Validate their evil data
- 53. 83 External Service DTO IAdapter Adapterimplements class OrderRepository implements IOrderRepo { public Order getById(id){ ... } } interface IOrderRepo { Order getById(id); } class OrderService { @Autowired IOrderRepository repo; ... { repo.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
- 54. 84 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
- 56. 89
- 57. 90 VOEntityid Domain Service Domain Service IExtSrv Adapter IRepo What code would you protect? Put it in the domain module Interfaces for External Services you consume Interfaces for Repositories Priceless Domain Logic Domain Objects
- 58. infra ExtSrv Adapter Repo implem 91 Façade DTO Validator Mapper VOEntityid Domain Service Domain Service IExtSrv Adapter IRepo F application The Onion Architecture Behold, a.k.a. Hexagonal, Ports-and-Adapters
- 60. 103 Façade DTO Validator Mapper VOEntityid Domain Service Domain Service IRepo Repo implem F application IExtSrv Adapter Adapter WS Interface DTO domain Pragmatic for decent apps, 2 modules are enough
- 61. 104 facade domain (+repo) infrastructure com.myorg.myapp. .order. … .product. … This grew too big! I need to restructure it.
- 62. Use-case Optimal Query 105 CALLS DEPENDS Breaking a Monolith DTO Facade Infra .order. … .product. … EVENT TX FK? SELECT MICRO… "Light CQRS" com.myorg.myapp. consistency 😱 "Clean Architecture" Replicate?
- 63. 106 archunit.org ArchRule rule = classes().that().resideInAPackage("..service..") .should().onlyBeAccessed() .byAnyPackage("..controller..", "..service..");
- 64. 108
- 65. 109 tardigrade
- 68. 114 Core Principles Modeling Data Organizing Logic The Onion Architecture Tests. Fear. Agenda
- 69. 115 Lots of Unit Tests are Good ! A sense of confidence Developer Courage Continuous Refactoring (It’s still a single )
- 70. 116 As you fight to write Unit Tests, the Production code gets simpler
- 71. 118 First couple of unit tests : The most valuable Test no. difficulty
- 72. Maintainable Tests Pure Functions No side effects. No dependencies. Mock-based In-memory Emulation or JPQL tests on H2/* db Fragile data fixtures On Real Systems Eg: Connecting to a real DB 119 𝑓 𝑥, 𝑦 = 𝑥2 + 𝑦2
- 73. infrastructure domain side effects 122 pure logic Unit Testing Like a Pro (the circle of purity)
- 74. ▪ 7 Virtutes of a Good Object ▪ NULL – the worst mistake in IT - https://dzone.com/articles/the-worst-mistake-of-computer-science-1 ▪ The Clean Architecture: - http://blog.8thlight.com/uncle-bob/2012/08/13/the-clean-architecture.html ▪ Some ☺ Programming Jargon - http://blog.codinghorror.com/new-programming-jargon/ ▪ Code quality: WTFs/minute - http://commadot.com/wtf-per-minute/ ▪ SOLID is WRONG - https://speakerdeck.com/tastapod/why-every-element-of-solid-is-wrong ▪ Good software is written 3 times - http://www.javaworld.com/article/2072651/becoming-a-great-programmer-- use-your-trash-can.html ▪ Prezi-like effect in PowerPoint 2016: “Morph” ▪ Value Objects vs Entity - http://enterprisecraftsmanship.com/2016/01/11/entity-vs-value-object-the- ultimate-list-of-differences/ ▪ Extends is bad - http://www.yegor256.com/2016/09/13/inheritance-is-procedural.html ▪ “Measure Don’t Ask” is TM of Kirk Pepperdine Further Reading 127
- 75. 128 Agenda VictorRentea.ro Core Principles Modeling Data Organizing Logic The Onion Architecture Tests. Fear.
- 76. 129 Core Principles VictorRentea.ro Modeling Data Organizing Logic The Onion Architecture Tests. Fear. AgendaTakeaways
- 77. 130 VictorRentea.ro Tests. Fear. Organizing Logic The Onion Architecture Modeling Data KISS: Avoid overengineering Magic to protect your Developers Takeaways
- 78. 131 VictorRentea.ro Tests. Fear. Organizing Logic The Onion Architecture Enemy data KISS: Avoid overengineering Magic to protect your Developers in your DTOs: keep them out Takeaways
- 79. 132 VictorRentea.ro Tests. Fear. Extract when it Grows The Onion Architecture KISS: Avoid overengineering Magic to protect your Developers : for SRP or DRY Enemy data in your DTOs: keep them out Takeaways
- 80. 133 VictorRentea.ro Extract when it Grows The Onion KISS: Avoid overengineering Magic to protect your Developers : for SRP or DRY Enemy data in your DTOs: keep them out , DIP: domain agnostic to externals Tests. Fear. Takeaways (Adapt® them)
- 81. 134 VictorRentea.ro Extract when it Grows The Onion KISS: Avoid overengineering Magic to protect your Developers : for SRP or DRY Enemy data in your DTOs: keep them out , DIP: domain agnostic to externals Tests: let them smash your design Takeaways (Adapt® them)
- 82. 135 KISS
- 84. 142 Put Passion In All That You Do!!
- 85. Thank You!!