Domain-Driven Design with Tender Loving Care (DDD with TLC)
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Evolving Legacy Software and Legacy Minds Presentation given at Domain-Driven Design Exchange at SkillsMatter in London (2017) (https://skillsmatter.com/conferences/8231-ddd-exchange-2017) and at Build Stuff Summer 2017 in Mallorca Spain (http://buildstuff.lt/summer/) Tips for helping legacy developers prepare their minds to rewrite their legacy software using modern practices and patterns. Guidance and strategies for consultants and team members.
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Domain-Driven Design with Tender Loving Care (DDD with TLC)
- 1. DDD WITH TLC EVOLVING LEGACY SOFTWARE & LEGACY MINDS Julie Lerman @JulieLerman about.me/julielerman * *Tender Loving Care
- 4. Why isn’t DDD ubiquitous?
- 5. DDD ORIGIN STORY? WHAT’S YOUR
- 6. My favorite computer book is the book by Eric Evans: "Domain-Driven Design". It's like poetry I think. It's not just great content, but you can read it many times and it reads like poetry. -Jimmy Nilssoninfoq.com/interviews/jimmy-nilsson-linq
- 7. DDD Hero!
- 8. “But I’m not a DDD expert!” Neither am I!
- 9. How can you spread DDD ….. to your clients & teammates?
- 16. Re-writing a legacy app Want new app to benefit from modern practices Recognize they are stuck in old thinking Already have buy-in from management MY TYPICAL CLIENTS Already have buy-in from management
- 17. I think we went through a pretty amazing process. I would be happy if others could learn from it. - “Client B” “ ”
- 18. Day of Review of their problem/domain/existing apps Multiple Days of Mob-Style [Refactoring] [Modeling] Review and Plan for Future ..or something totally different, defined by the challenge Typical Consulting Engagement Overview
- 19. Breaking down problems into digestible problems Gaining new perspective on their own problem domain Organizing Flow of Data What I Try to Achieve While On Site
- 21. EMPATHY EXPERIENCE CONFIDENCE PERSISTENCE INSTINCT OBJECTIVITY MENTORING
- 22. Focus is on Their problems Their domain
- 25. “Guidance” “Ideas that helped me” “Learning some ideas will lead to understanding others” “Rules” “Every programmer must know” “DDD is big. Buckle up!” “Rules” “Every programmer must know” “DDD is big. Buckle up!”
- 26. REDUCE STRESS
- 27. BOUNDED CONTEXT
- 28. HOW BOUNDED CONTEXT CHANGED MY LIFE Julie Lerman @JulieLerman about.me/julielerman Future conference talk…
- 29. Breaking big problems into small digestible problems
- 30. Customer Management Sales Orders Shipping Human Resources Start with a simplistic example, then dive into their domain Inventory Customer Service
- 31. BUT OMG!
- 32. Everything is related! We have to call these methods! You’re breaking everything!!!! BUT OMG! You still have FKs to pass around DDD has proven patterns for interaction My favorite “broken arm” analogy
- 33. We need Customer everywhere! We’ll be duplicating everything! BUT OMG!
- 34. Customer is a great domain type to explore Sales Orders Customer Management Inventory Shipping Human Resources Customer Customer Customer Service Customer Customer
- 35. Sales Orders Customer Management Inventory Shipping Human Resources Customer Customer Customer Service Customer Customer Because it’s not always a customer
- 36. PICK YOUR POISON
- 37. “Puppet Master” (aka Domain Services) LibraryBook.CheckMeOut(patron) Patron.CheckOutABook(book) PM.BookBorrowed(book,patron) PM.RequestBookByAuthor(name) LibraryBook.GetMyDetailsFromTheDB
- 39. Client A: 2 years into a rewrite
- 42. Identify Simplest BC Extract Huge Refactor Effort
- 44. Client B: Embarking on rewrite
- 46. AND EDUCATIONAL MODELING IS HARD
- 49. Database is not the model Database table names are not entity names Forget the database Forget the database Focus on the domain Forget the database. We aren’t inserting new clients. What happens if a debtor moves to a new company What happens when a debtor’s debt is paid off?
- 51. Is responsible for creation and maintenance of
- 52. Is responsible for creation and maintenance of Is responsible for creation and maintenance of
- 53. Keep at it until... everyone at the table is confident they’ve made the right decisions. But…
- 54. Good Design is Imperfect Design Eric Evans Right here, about an hour ago “ ” -
- 55. Client C: Embarking on rewrite Using a unique idea
- 57. Client A: Hired a Practice Manager Client B: Reorganized the team Also, showered me with gifts Client C: Stuck with their unique design
- 58. Build trust Hand-hold Don’t tell, just do Keep reducing the stress Be kind Its about them, not you
- 59. You can be a DDD hero by starting them on their DDD path
- 60. DDD WITH TLC EVOLVING LEGACY SOFTWARE & LEGACY MINDS Julie Lerman @JulieLerman about.me/julielerman * *Tender Loving Care
Editor's Notes
- I Am Groot!