Fundamental Domain-Driven Design for Microservices

Slides of the talk I gave at JUG Saxony Day 2016.

@springcentral

Transcript

1. © 2014 SpringOne 2GX. All rights reserved. Do not distribute without permission. DOMAIN-DRIVEN DESIGN / OLIVERGIERKE ƻ OGIERKE@PIVOTAL.IO FUNDAMENTAL FOR MICROSERVICES
4. 4 http://www.infoq.com/minibooks/domain-driven-design-quickly
6. Implementing Domain-Driven Design 6
7. Value objects 7
8. Stringly typed code 8 public class Customer { private Long id; private String firstname, lastname, email; … }
9. Stringly typed code 9 public class SomeService { public void createUser(String firstname,
 String lastname, String email) { … } }
10. 10 public class Customer { private Long id; private Firstname firstname; private Lastname lastname; private EmailAddress emailAddress; … }
11. Value Objects are a
 PITA to build in
 some languages. 11
12. Still, they’re worth it. 12 See „Power Use of Value Objects in DDD“ by Dan Bergh Johnsson.
13. Lombok — putting the spice back into Java. 13
14. 14 @Value public class Customer { UUID id = UUID.randomUUID(); Firstname firstname; Lastname lastname; EmailAddress email; @Value static class EmailAddress { String value; } }
15. Entities & Aggregates 16
16. 17 Order LineItem Product Invoice Customer Payment Address Email
17. 17 Order LineItem Product Invoice Customer Payment Address Email
18. Persistence technology
 VS.
 Domain model 18
19. Aggregate =
 Entity + Repository 19
20. 20 Order LineItem Product Invoice Customer Payment Address Email
21. Bounded Context 21
22. Order LineItem Product Invoice Customer Payment Address
23. 23 Shipping Accounting Catalog Orders User
 Registration
24. 23 Shipping Accounting Catalog Orders User
 Registration Accounting Payment information Billing Address Shipping Shipping address Customer Product
25. Domain-Driven Design & Monoliths 24
26. Avoid technologies that get in your way. 25
27. How to enforce
 context boundaries? 26
28. What about
 consistency? 27
29. References between Bounded Contexts? 28
30. Domain Events 29
31. 30 Level 0: No events at all
32. 30 Level 0: No events at all Level 1: Explicit operations
33. If you’re calling two setters in a row, you’re missing a concept. 31
34. 32 Level 0: No events at all Level 1: Explicit operations Level 2: Some operations as events
35. State transitions
 become domain
 events. 33
36. 34 Level 0: No events at all Level 1: Explicit operations Level 2: Some operations as events Level 3: Event Sourcing
37. Domain-Driven Design & Microservices 35
38. Bounded contexts 
 define system
 boundaries. 36
39. 37 Shipping Accounting Catalog Orders User
 Registration Accounting Payment information Billing Address Shipping Shipping address Customer Product
40. 38 Shipping Accounting Catalog Orders User
 Registration Accounting Shipping
41. 39 Shipping Accounting Catalog Orders User
 Registration Accounting Shipping HTTP Messaging
42. Architecture is less
 likely to deteriorate
 as it’s harder to
 violate boundaries. 40
43. Restructuring
 service boundaries
 is much harder. 41
44. Inter-Context communication
 becomes remote
 communication. 42
45. Accept and embrace eventual consistency between services. 43
46. Domain Events 44
47. REST & Messaging 45
48. Domain events
 become state
 transitions. 46
49. Hypermedia for state transition and explicit events. 47
50. Thanks! 48