1. GET /presentation HTTP/1.1
HTTP/1.1 200 OK
Content-Type: application/json
{
"what": "The REST And Then Some",
"where": "Nordic APIs 2016 Platform Summit",
"when": "2016-10-25T14:40+02:00"
}

2. Asbjørn Ulsberg
Business Architect
Web, API, Interfaces

4. 1941
The Garden of Forking Paths
Jorge Luis Borges

6. “Hypertext”
“Hypermedia”
1963

7. 1968
“The Mother Of All Demos”
oN-Line System

8. 1987

9. 1989
“WorldWideWeb”

10. 2000
Architectural Styles and the Design of
Network-based Software Architectures
By
“Representational State Transfer”“REST”
Roy Thomas Fielding

11. Defining REST

12. POST Does ”something” with the resource
GET Retrieves the resource
PUT Replaces or creates the resource.
PATCH Given right state in client, apply a diff operation
DELETE Delete the resource
…
Defining REST: CRUD

13. Defining REST: URIs
http://api.com/harddrives/format?drive=c
http://api.com/orders/getOrderById?id=13
http://api.com/orders/13/edit-form
http://api.com/orders/13
http://api.com/731bef1e-8ffa-11e6-96e8

14. Defining REST: URIs
URI Method Description
http://api.com/v1/customers POST Creates a new customer
http://api.com/v1/customers/{id} GET Retrieves customer
http://api.com/v1/customers/{id} PUT Updates customer
http://api.com/v1/customers/{id} DELETE Deletes customer
http://api.com/v1/customers/{id}/orders GET Retrieves customer’s orders
http://api.com/v1/customers/{id}/notes GET Retrieves customer’s notes

15. Defining REST: URIs

16. Defining REST: URIs

17. Defining REST: URIs
URI Method Description
http://api.com/v1/customers POST Creates a new customer
http://api.com/v1/customers/{id} GET Retrieves customer
http://api.com/v1/customers/{id} PUT Updates customer
http://api.com/v1/customers/{id} DELETE Deletes customer
http://api.com/v1/customers/{id}/orders GET Retrieves customer’s orders
http://api.com/v1/customers/{id}/notes GET Retrieves customer’s notes

18. Defining REST: URIs
URI Method Description
http://api.com/v1/customers POST Creates a new customer
http://api.com/v1/customers/{id} GET Retrieves customer
http://api.com/v1/customers/{id} PUT Updates customer
http://api.com/v1/customers/{id} DELETE Deletes customer
http://orders.com/orders-for-customer/{id} GET Retrieves customer’s orders
http://api.com/v1/customers/{id}/notes GET Retrieves customer’s notes

19. Defining REST: URIs
URI Method Description
http://api.com/v1/customers POST Creates a new customer
http://api.com/v1/customers/{id} GET Retrieves customer
http://api.com/v1/customers/{id} PUT Updates customer
http://api.com/v1/customers/{id} DELETE Deletes customer
http://orders.com/orders-for-customer/{id} GET Retrieves customer’s orders
http://api.com/v2/customers/{id}/notes GET Retrieves customer’s notes

20. Defining REST: URIs
URI Method Description
http://api.com/v2/customers POST Creates a new customer
http://api.com/v2/customers/{id} GET Retrieves customer
http://api.com/v2/customers/{id} PUT Updates customer
http://api.com/v2/customers/{id} DELETE Deletes customer
http://orders.com/orders-for-customer/{id} GET Retrieves customer’s orders
http://api.com/v2/customers/{id}/notes GET Retrieves customer’s notes

21. What is the best practice for
versioning a REST API?

23. REST

24. I feel warmer and more relaxed
in Spanish

25. German makes me reason
more carefully

26. REST: Constraints
1. Client-Server
2. Stateless
3. Cacheable
4. Layered
5. Code on demand (optional)
6. Uniform Interface
1. Identification of resources
2. Manipulation of resources
3. Self-descriptive messages
4. Hypermedia as the engine of application state (HATEOAS)

27. REST: Constraints
1. Client-Server
2. Stateless
3. Cacheable
4. Layered
5. Code on demand (optional)
6. Uniform Interface
1. Identification of resources
2. Manipulation of resources
3. Self-descriptive messages
4. Hypermedia as the engine of application state (HATEOAS)

28. Hypermedia as the engine of
application state is a REST constraint.
Not an option. Not an ideal.
Hypermedia is a constraint. As in,
you either do it or you aren’t doing
REST.

29. Hypermedia

30. Hypermedia: Affordances

31. Hypermedia: Affordances
Do people know what to do based on
what they see?

32. Hypermedia: Affordances
Do machines know what to do based on
what they see?

33. Hypermedia
<a href="/toaster">Toaster</a>
<img src="toaster.jpeg" alt="Toaster">
<video src="toaster.mp4">Toaster</video>
<form action="/toaster" method="post" rel="on">
<button type="submit"
name="state"
value="on">Turn on</button>
</form>

34. Hypermedia
<a href="/toaster">Toaster</a>
<img src="toaster.jpeg" alt="Toaster">
<video src="toaster.mp4">Toaster</video>
<form action="/toaster" method="post" rel="on">
<button type="submit"
name="state"
value="on">Turn on</button>
</form>

35. <a href="/toaster">Toaster</a>
<img href="toaster.jpeg" alt="Toaster">
<video href="toaster.mp4">Toaster</video>
<form href="/toaster" method="post" rel="on">
<button type="submit"
name="state"
value="on">Turn on</button>
</form>

36. <id href="/toaster" title="Toaster">
<image href="toaster.jpeg" title="Toaster">
<video href="toaster.mp4" title="Toaster">
<operation href="/toaster" method="put" rel="on">
<expects name="state" value="on" />
</operation>

37. { "id": "/toaster", "title": "Toaster" }
{ "image": "toaster.jpeg", "title": "Toaster" }
{ "video": "toaster.mp4", "title": "Toaster" }
{ "operation": "/toaster", "method": "PUT", "rel": "on",
"expects": { "state": "on" }
}

38. { "id": "/toaster", "title": "Toaster" }
{ "image": "toaster.jpeg", "title": "Toaster" },
{ "video": "toaster.mp4", "title": "Toaster" }
"operation": {
"rel": "on",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "on" }
}

39. {
"id": "/toaster",
"links": [
{ "image": "toaster.jpeg", "title": "Toaster" },
{ "video": "toaster.mp4", "title": "Toaster" }
],
"operations": [{
"rel": "on",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "on" }
}]
}

40. Hypermedia: State Machine

42. OnOff Shutting down
Shut Down
Off
Shut Down
Upper Limit Lower Limit
Heating
Idle
Do/Turn Off
Heater
Turn On

43. Off
GET /toaster HTTP/1.1

44. Off
HTTP/1.1 200 OK
{
"id": "/toaster",
"state": "off",
"operations": [{
"rel": "on",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "on" }
}]
}

45. Off
HTTP/1.1 200 OK
{
"id": "/toaster",
"state": "off",
"operations": [{
"rel": "on",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "on" }
}]
}

46. Off
PUT
/toaster
{ "state": "on" }

47. Off
PUT
/toaster
{ "state": "on" }

48. Off
PUT
/toaster
{
"state": "on"
}

49. Off
Turn On
On
PUT /toaster HTTP/1.1
{
"state": "on"
}
HTTP/1.1 200 OK
{
"id": "/toaster",
"state": "on",
"strength": 0,
"operations": [{
"rel": "off",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "off" }
}, {
"rel": "strength",
"method": "PUT",
"href": "/fcef93ba988011e6833f",
"expects": {
"strength": [1, 2, 3, 4, 5, 6]
}
}]
}

50. On
PUT
/fcef93ba988011e6833f
{
"strength": [1, 2, 3, 4, 5, 6]
}

51. On
PUT /fcef93ba988011e6833f
{
"strength": [1, 2, 3, 4, 5, 6]
}

52. On Heating
HTTP/1.1 200 OK
{
"id": "/toaster",
"state": "heating",
"strength": 3,
"operations": [{
"rel": "off",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "off" }
}, {
"rel": "strength",
"method": "PUT",
"href": "/fcef93ba988011e6833f",
"expects": {
"strength": [1, 2, 3, 4, 5, 6]
}
}]
}
PUT /fcef93ba988011e6833f HTTP/1.1
{
"strength": 3
}

53. Heating
/toaster

54. Upper Limit
Idle
Do/Turn Off
Heater
Heating
HTTP/1.1 200 OK
{
"id": "/toaster",
"state": "idle",
"operations": [{
"rel": "off",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "off" }
}, {
"rel": "strength",
"method": "PUT",
"href": "/fcef93ba988011e6833f",
"expects": {
"strength": [1, 2, 3, 4, 5, 6]
}
}]
}
GET /toaster HTTP/1.1

55. Shut Down
Shutting down
Idle
Do/Turn Off
Heater
GET /toaster HTTP/1.1HTTP/1.1 200 OK
{
"id": "/toaster",
"state": "shutting-down",
"operations": []
}

56. Shutting down
GET /toaster HTTP/1.1
Off
HTTP/1.1 200 OK
{
"id": "/toaster",
"state": "off",
"operations": [{
"rel": "on",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "on" }
}]
}

57. {
"id": "/toaster",
"state": "off",
"slot": "/toaster/slot",
"operations": [{
"rel": "on",
"method": "PUT",
"href": "/toaster",
"expects": { "state": "on" }
}]
}

58. Questions?

59. Thank You!
- @asbjornu
- asbjorn.ulsberg@payex.com
- slack.httpapis.com
Asbjørn Ulsberg