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DDD & REST — Domain-Driven APIs for the web

DDD & REST — Domain-Driven APIs for the web

Slides of the talk I gave a Java Forum Nord 2016.

@springcentral

Oliver Drotbohm

October 20, 2016
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  1. 3

  2. 10

  3. Stringly typed code 13 public class Customer { private Long

    id; private String firstname, lastname, email; … }
  4. Stringly typed code 14 public class SomeService { public void

    createUser(String firstname,
 String lastname, String email) { … } }
  5. 15 public class Customer { private Long id; private Firstname

    firstname; private Lastname lastname; private EmailAddress emailAddress; … }
  6. Still, they’re worth it. 17 See „Power Use of Value

    Objects in DDD“ by Dan Bergh Johnsson.
  7. 19 @Value public class Customer { UUID id = UUID.randomUUID();

    Firstname firstname; Lastname lastname; EmailAddress email; @Value static class EmailAddress { String value; } }
  8. 32 Shipping Accounting Catalog Orders User
 Registration Accounting Payment information

    Billing Address Shipping Shipping address Customer Product
  9. 36 Level 0: No events at all Level 1: Explicit

    operations Level 2: Some operations as events
  10. 39 Level 0: No events at all Level 1: Explicit

    operations Level 2: Some operations as events Level 3: Event Sourcing
  11. 49 Amount of domain knowledge in the client Amount of

    protocol knowledge in the client Coupling to the server Non-hypermedia
 based systems Hypermedia
 based systems
  12. API evolvability is key
 in a system of systems 50

    See „Evolving Distributed Systems“
  13. 51 GET /orders { „_links“ : { „cancel“ : {

    „href“ : … }, … „createdDate“ : …, „status“ : „Payment expected“ … }
  14. 54 GET /order/42 { „_links“ : { „cancel“ : {

    „href“ : … }, … „createdDate“ : …, „status“ : „Payment expected“ … }
  15. 58 GET /order/42 { „_links“ : { „cancel“ : {

    „href“ : … }, … „createdDate“ : …, „status“ : „Payment expected“ … }
  16. 62 Aggregate Root / Repository Collection / Item Resources IDs

    URIs @Version ETags Last Modified Property Last Modified Header Relations Links
  17. Method URI Action Step POST /orders Create new order 1

    POST/PATCH /orders/{id} Update the order (only if "payment expected") 2 DELETE /orders/{id} Cancel order (only if "payment expected") 3 PUT /orders/{id}/payment Pay order (only if "payment expected") 4 Barista preparing the order GET /orders/{id} Poll order state 5 GET /orders/{id}/receipt Access receipt DELETE /orders/{id}/receipt Conclude the order process 6
  18. Method Resource type Action Step POST orders Create new order

    1 POST/PATCH update Update the order 2 DELETE cancel Cancel order 3 PUT payment Pay order 4 Barista preparing the order GET order Poll order state 5 GET receipt Access receipt DELETE receipt Conclude the order process 6
  19. Web Service Repository - Orders Spring Data Spring Data
 REST

    Payment Spring Data Manual
 implementation Manual
 implementation