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Introduction to-ddd
Domain-driven design is a set of principles and patterns for focusing design effort on the core domain of an application. It involves creating a model that reflects the key domain concepts and then using that model throughout the software design and implementation. This includes using a ubiquitous language shared between technical and domain experts, elaborating the model through collaborative discussion, and representing the model through diagrams, specifications, tests and code.
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Introduction to-ddd
- 1. Domain Driven Design softwarethat reflects the business domain John Ferguson Smart
- 2. So who isthis guy, anyway? Consulta nt Trainer Mentor Author Speaker Coder John Fer guson S mar t
- 3. What is Domain-DrivenDesign?
- 4. Domain-driven design isnot a technology or a methodology.
- 5. It’s a setof principles and patterns for focusing design effort where it matters most.
- 6.
- 7. Basic principles Focus on the domain Domain design is based on a model
- 8. Basic principles A UbiquitousLanguage... ...and a shared vision
- 9. So what’s amodel?
- 13. How do yourepresent your domain model?
- 14. How do yourepresent your domain model? Customer Account (UML) Diagrams? Branch
- 15. How do yourepresent your domain model? Detailed specifications?
- 16. How do yourepresent your domain model? Account Holder withdraws cash As an account holder I want to withdraw cash from an ATM so that I can get money out when the bank is closed Scenario 1: Account has sufficient funds Given the account balance is $100 And the card is valid And the machine contains enough money Free text? When the Account Holder requests $20 Then the ATM should dispense $20 And the account balance should be $80 And the card should be returned Scenario 2: Account has insufficient funds Given the account balance is $10 And the card is valid And the machine contains enough money When the Account Holder requests $20 The ATM should not dispense any money
- 17. How do yourepresent your domain model? @Test public void aCashWithdrawalShouldDeductSumFromBalance() { Account account = new Account(); account.makeDeposit(100); account.makeCashWithdraw(60); assertThat(account.getBalance(), is(40)); } Automated tests?
- 18. How do yourepresent your domain model? class Account(val owner : Customer, val accountNumber : String, val accountType : AccountType, var balance : Double) { def deposit(amount : Double) { balance += amount } def withdraw(amount : Double) { balance -= amount } } Code? class Customer(val firstName : String, val lastName : String) { createAccount(accountType : AccountType) : Account } class AccountType extends Enumeration { val Current = value("CURRENT") val Savings = value("SAVINGS") }
- 19. The model isthe mental representation Everything else is just a communication tool
- 20.
- 21. Elaborating the model Acollaborative exercise
- 22. Elaborating the model ...basedon a common language
- 23. Elaborating the model AccountHolder withdraws cash As an account holder I want too withdraw cash from an ATM so that I can get money out when the bank is closed @Test public void aCashWithdrawalShouldDeductSumFromBalance() { Account account = new Account(); account.makeDeposit(100); account.makeCashWithdraw(60); assertThat(account.getBalance(), is(40)); } ...and expressed at all levels
- 24. Elaborating the model Anevolutionary process
- 25. Elaborating the model So testing is essential
- 26. Elaborating the model Test ...automated testing is essential
- 27.
- 28. Domain-Driven Design architecture User Interface Presenta(on Layer Service layer Applica(on Layer Stateless domain knowledge and Domain Layer business logic supporting libraries Infrastructure Layer persistence messaging
- 29. Domain-Driven Design architecture Entities • Identify and state • Persistence
- 30. Domain-Driven Design architecture Value Objects • No conceptual identity • Immutable
- 31. Domain-Driven Design architecture Services • Domain-level services • Stateless
- 32. Domain-Driven Design architecture Repositories • Data retrieval • Abstraction of the persistence layer
- 33. Domain-Driven Design architecture Factories • Creation of complex entities
- 34. Application code shouldbe a reflection of the business domain John Ferguson Smart Email: john.smart@wakaleo.com Web: hAp://www.wakaleo.com TwiAer: wakaleo