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Facade Roles - Summary
• Converts DTOs Entities
• inline, via [Auto-]Mappers, or Dto constructors/methods.
• Validates inputs
• @javax.validation.NotNull, if ...
• Transaction / use-case
• Except in high-TPS systems
• Orchestrates the workflow of a 🧠 use-case
• By delegating to lower-level components](https://image.slidesharecdn.com/cleanpragmaticarchitecturedevflix-220110202926/85/Clean-pragmatic-architecture-devflix-28-320.jpg)
Uploaded byVictor Rentea
Clean pragmatic architecture @ devflix
Victor Rentea introduces himself as a Java Champion, trainer, and speaker who focuses on topics like Hibernate, Spring, Java 8/FP, architecture, clean code, unit testing, reactive programming, and Java performance. He advocates building a deep, rich domain model with value objects and entities that encapsulate logic and enforce invariants. The document provides guidance on applying principles like separating concerns with layers, dependency inversion, and avoiding anemic domain models in order to build flexible, testable systems that are decoupled from frameworks and external dependencies.
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Clean pragmatic architecture @ devflix
- 1.
- 2. Hi, I'm VictorRentea Java Champion – drinking since 2006 Trainer – 3000+ devs / 80+ companies, since 2013 Speaker – Conferences & Meetups Hibernate Spring Java8/FP Java Performance Secure Coding Reactive Architecture Clean Code Unit Testing
- 3. $ Hibernate Spring Java8/FP Architecture CleanCode Unit Testing Masterclass Company Training Video Courses YouTube Channel 💗 Join My Community Blog @victorrentea VictorRentea.ro victorrentea@gmail.com Java Performance Secure Coding Reactive
- 4. 172 VictorRentea.ro a trainingby Chapter 1. Data Structures
- 5. 173 VictorRentea.ro a trainingby Can I have a chicken?
- 6. The data structurethey send you The data structure you want to use in your core logic DTO domain Object
- 7. 175 VictorRentea.ro a trainingby DTOs* are Evil *Data Transfer Objects – data structures that move across APIs
- 8. 176 VictorRentea.ro a trainingby ☢ Beware of Foreign Data Structures ☢ ➢ Bloated (more fields than you need) ➢ Flat ➢ Different perspective 🐔 (bounded context) ➢ Fixed design (often generated or in client-lib) ➢ Mutable (pain from frameworks otherwise) ➢ No constraints (nulls, validation, invariants) ➢ Diverging in time (v2) We 💗 small, cohesive data structures We 💗 Logic next to data (OOP) We 💗 Immutable objects We 💗 Deep, Rich Domain Model We 💗 Models to guard their invariants We want control over our structures Because DTOs are: In our core logic: We 💗 Structures tailored to our problem
- 9. 177 © VictorRentea.ro atraining by Don't implement complex logic on foreign data structures Elders Wisdom What's complex? What's foreign?
- 10. 178 VictorRentea.ro a trainingby Bounded Context A (TeamA) The Curious Case of Nanoservices DTOs can be shared within the same Bounded Context (team) =tiny microservice eg. 5 devs maintaining 20 microservices 1 2 3 Bounded Context B (TeamB) X But not with others What's foreign?
- 11. 179 VictorRentea.ro a trainingby ⚠ Returning entities as JSON ⚠ ➢ Couples your clients to your internal entity structure ➢ Is risky to marshal and of course...
- 12. 180 VictorRentea.ro a trainingby Decouple DTO Domain Model < > Price: more classes + more mapping Exception: Boundary Systems = Huge Adapters without own Domain Software Ecosystem A - Manually Crafted DTO - Generated DTOs: XML: .xsd/.wsdl ➔ xjc JSON: .yaml ➔ swagger-gen Auto-Generated Mappers
- 13. 181 VictorRentea.ro a trainingby Auto-Generated Mappers Converting Entity DTO with as long as the field names match, mapping happens automatically eg MapStruct Temptation to keep the models in sync Entities and DTOs must be allowed to diverge Customer.firstName CustomerDto.firstName War Stories: When mapping gets complex, deep knowledge of MapStruct is required ➔ Consider switching to manual mapping (simpler) ?
- 14. 182 © VictorRentea.ro atraining by Don't implement complex logic on foreign data structures Elders Wisdom
- 15. 183 VictorRentea.ro a trainingby Chapter 2. Logic
- 16.
- 17. 185 VictorRentea.ro a trainingby The Code - anonymous developer
- 18. 186 VictorRentea.ro a trainingby Layers SUB-DOMAINS Controller Service Repository APIs order Product user customer API infrastructure too complex ➔
- 19. 187 VictorRentea.ro a trainingby Layers Controller Repository APIs Facade / Application Service Layered Architecture DOMAIN Service
- 20. 188 VictorRentea.ro a trainingby Controller Repository call direction pull orchestration up, let Repos trivial Relaxed Layered Architecture allows skipping layers Layered Architecture DOMAIN Service Facade / Application Service
- 21. 190 VictorRentea.ro a trainingby by pushing details in lower-level classes Muscle Fascicle Fiber Myofibril Myofilaments Goal = Simplify the top-level view of your flow Facade = Separation by Layers of Abstraction
- 22. 191 Code is NOTa Construction
- 23.
- 24. 193 VictorRentea.ro a trainingby requirements Logic Service Facade HOW? Entities OOP 1) One class/use-case GetOrderByIdService - ⚠ tiny class PlaceOrderService - ⚠ god class -or- 2) N use-cases in a class class OrderFacade { ⚠ god class placeOrder() getOrderById() } 5-10%..more?💪 Continuously Extract ApplicationService DomainService simplify the most complex flows
- 25. 194 VictorRentea.ro a trainingby Mapper DTO Facade Facade Domain Service Domain Service Domain Services Ideas inspired by the book Java EE Patterns - Rethinking Best Practices, by Adam Bien Push Domain Logic into Start implementing every use-case in a Facade For trivial User Cases a method is enough eg. getOrderById When logic gets complex, or has to be reused (evolutionary architecture)
- 26. 195 VictorRentea.ro a trainingby Mapper DTO Facade Domain Service Domain Service take and return only Domain Objects or primitives Don't Depend on DTOs Domain Boundary DTOs are Evil VO Entity id Convert them to your Domain Objects ASAP Domain Services
- 27. 196 VictorRentea.ro a trainingby Cohesive Domain Services OrderService PlaceOrderService ⚠Bloat Risk, if Order is a large Entity
- 28. @VictorRentea 197 Facade Roles -Summary • Converts DTOs Entities • inline, via [Auto-]Mappers, or Dto constructors/methods. • Validates inputs • @javax.validation.NotNull, if ... • Transaction / use-case • Except in high-TPS systems • Orchestrates the workflow of a 🧠 use-case • By delegating to lower-level components
- 29.
- 30. 199 VictorRentea.ro a trainingby Domain Service Domain Service External Service domain DTO call may get in
- 31. 200 VictorRentea.ro a trainingby External Service DTO Adapter Domain Service Domain Service domain
- 32. 201 VictorRentea.ro a trainingby External Service DTO Adapter Domain Service Domain Service <dependency> domain infrastructure
- 33. VictorRentea.ro 202 External Service DTO IAdapter Adapter implements class UserApiClient implementsIUserAdapter { 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
- 34. 203 VictorRentea.ro a trainingby 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
- 35. 204 VictorRentea.ro a trainingby calls <dependency> higher-level module lower-level module RMI, HTTP gRPC.. FTP Queue DB DTO Dependency Inversion
- 36. 206 VictorRentea.ro a trainingby Stop Code Dependencies from complex logic ➔ externals Dependency Inversion Package Dependency Checks - via 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
- 37. 207 VictorRentea.ro a trainingby An Agnostic Domain lets you focus on YOUR problem Agnostic Domain
- 38. 209 VictorRentea.ro a trainingby 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 Msg Handler Adapter Spring Data IRepo
- 39. 210 VictorRentea.ro a trainingby 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 "Light-CQRS" Selecting DTOs directly from queries
- 40. 211 VictorRentea.ro a trainingby 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 Learn Hibernate: https://www.youtube.com/watch?v=iw0tOx7Zbjc
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- 42. 213 VictorRentea.ro a trainingby Anemic Domain Model ("classic" approach) Rich Domain Model (Domain-Driven Design) vs Getters & Setters for all fields All logic written in Services Getters but less setters Logic using fields of class X stays in X Self-validating model eg. Address constructor validates its consistency Aggregates as consistency boundaries Invariants enforced by Services eg. Shipment requires a postal code, unless city=Bucharest
- 43. 214 VictorRentea.ro a trainingby Chapter 3. Value Objects
- 44. 215 VictorRentea.ro a trainingby How many fields it has? Can you make it immutable? Tell me about that big entity ... How do you feel about moving logic inside?
- 45. 216 VictorRentea.ro a trainingby 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:
- 46. 217 VictorRentea.ro a trainingby Conceptual Whole Money {amount, currency} FullName {first, last} Changes Together LastModified-Time/-ByUser How to identify Value Objects? Screens InvoicingDetails Moves Together PriceComputationInput
- 47. 218 VictorRentea.ro a trainingby Key Points DTOs are evil Build a Deep, Rich Domain Model Protect your Domain with DIP or ArchUnit Don't let persistence concerns influence your Model design Continuously Refactor to keep code suple The entire team should understand the Design Goals Be Pragmatic. Think Critically! dogmas
- 48. @victorrentea VictorRentea.ro victorrentea@gmail.com == What Iteach == Thank You !