Object-Oriented Lessons for a Service-Oriented World

Many of the same principles that guide our software design can guide our software architecture. Rarely, though, do we see the same practices applied to our services and APIs, leaving us with tightly coupled and difficult to extend service-oriented architectures. Consider looking at your services as objects and your APIs as messages. Service-oriented applications are complex, and the best way to fend off complexity is though object-oriented design.

Transcript

1. object-oriented lessons for a service-oriented world Railsberry 2013 - Krakow, Poland RailsConf 2013 - Portland, Oregon
2. Chris Kelly in meatspace
3. amateurhuman on the interwebs
5. This is a conversation about ideas. It is not a prescription for how you have to do it.
6. San Francisco Krakow Portland Crieff Hydro Warsaw Denver
7. Lynx (web browser) - Wikipedia, the free encyclopedia (p1 of 26) #Edit this page Wikipedia (en) copyright Wikipedia Atom feed Lynx (web browser) From Wikipedia, the free encyclopedia Jump to: navigation, search Not to be confused with Links (web browser) or LynxOS. Original author(s) Lou Montulli, Michael Grobe, Charles Rezac Developer(s) Thomas Dickey Initial release 1992 (1992) Lynx is a highly configurable text-based web browser for use on cursor-addressable character cell terminals.^[1]^[2] It is the oldest web browser currently in general use and development,^[3] having started in 1992 and as of 2013^[update], 21 years later, still in use and development. Arrow keys: Up and Down to move. Right to follow a link; Left to go back. H)elp O)ptions P)rint G)o M)ain screen Q)uit /=search [delete]=history list
9. animated gifs
11. MONORAIL
12. SOFTWARE SO WHAT YOU WANT IS ARCHITECTURE
13. Software architecture? Did you just tell me to go F*@< myself?
14. NETWORK-BASED APPLICATION SOFTWARE
15. Monorail Cache Database
16. Monorail Cache Database
17. Monorail Cache Database
18. Monorail Cache Database
19. Special Snowflake YouR is a application
20. Special Snowflake YouR is a application that breaksevery time you change anything
22. DEPENDENCIES
23. OBJECT ORIENTED DESIGN D E P E NDE N C I E S
24. State Behavior a thorough and complete analysis of objects* *100% accurate 0% of the time
25. State Behavior a thorough and complete analysis of objects* *100% accurate 0% of the time
26. State Behavior a thorough and complete analysis of objects* ^ MORE *100% accurate 0% of the time
27. Cool story, bro. But we’re talking about applications talking over http.
28. HELLO my name is HTTP Object Model
29. HELLO my name is REST
30. DRY SOLID LAW OF DEMETER seperation of concerns Single-responsibility principle Open-Closed Liskov Substitution Interface Segregation Dependency Inversion Don’t Repeat Yourself Encapsulation
31. Single Responsibility Do one thing, and do it well. Do the smallest thing possible, and nothing more. Make things as simple as possible, but not simpler. Cohesive, everything it does should be related to its purpose.
32. Repeat Yourself Every piece of knowledge within a system must have single, unambiguous, authoritative representation
33. Depend on Behavior not on data
34. Dependency Inversion Dependency Inversion
35. DEMETER LAW OF More like guidelines of Demeter
36. Dependency Injection
37. Service Database Service Service Service Service Service
38. Public Service Announcement Cache is King Network-based software applications mean more overhead. Serialization is expensive, do yourself a favor and don’t do it when you don’t have to. Cache-control and etag headers are a services best friend. Caching is a first order feature.
39. MESSAGES
40. class Orders < ApplicationController::Base def index @orders = Order.all respond_to do |format| format.html format.json { render json: @orders } end end end Not a Application Programming Interface
41. Nouns VERBS In object-oriented design, classes are And our messages are often
42. /getUsers /verifyEmailAddress /getOrders /updateShippingAddress
43. GET PUT POST DELETE HTTP already has some verbs But they’re kind of crudy
44. What about hypermedia?
45. This is not your Rails’ REST https://api.example.org/accounts/23/orders/37
46. REST HYPERMEDIA COMBINES A MEDIA TYPE & LINK RELATIONS
47. { “_links”: { “self”: { “href”: “/orders” }, “next”: { “href”: “/orders?page=2” }, “find”: { “href”: “/orders/{id}”, “templated”: true }, “_embedded”: { “orders”: [{ “_links”: { “self”: { “href”: “/orders/123” } }, “total”: 1337.00 Behavior { { State
48. { “_links”: { “self”: { “href”: “/orders” }, “next”: { “href”: “/orders?page=2” }, “find”: { “href”: “/orders/{id}”, “templated”: true }, “_embedded”: { “orders”: [{ “_links”: { “self”: { “href”: “/orders/123” }, “cancel”: { “href”: “/orders/123/cancel” } }, Behavior { { State
49. Approaching a Behavioral API
50. Get a single issue GET /repos/:owner/:repo/issues/:number { "url": "https://api.github.com/repos/octocat/Hello-World/issues/134 "html_url": "https://github.com/octocat/Hello-World/issues/1347", "number": 1347, "state": "open", "title": "Found a bug", "body": "I'm having a problem with this.", "user": { "login": "octocat", "id": 1,
51. Close an issue PATCH /repos/:owner/:repo/issues/:number { "state": "closed" }
52. Get a pull request GET /repos/:owner/:repo/pulls/:number { "url": "https://api.github.com/octocat/Hello-World/pulls/1", "html_url": "https://github.com/octocat/Hello-World/pulls/1", "diff_url": "https://github.com/octocat/Hello-World/pulls/1.diff", "patch_url": "https://github.com/octocat/Hello-World/pulls/1.patch "issue_url": "https://github.com/octocat/Hello-World/issue/1", "number": 1, "state": "open", "title": "new-feature", "body": "Please pull these awesome changes",
53. Merge Button PUT /repos/:owner/:repo/pulls/:number/merge { # Optional Message "message": "YOLO" } TM
54. The Good The Bad The Ugly Link relations are already appearing in media types You can implement custom media types The necessary HTTP verb is a missing
55. Thanks for the chat. @amateurhuman