Rest and Rails

REST And rails
Chhorn Chamnap
YoolkMango
15 - July - 2010

Agenda
REST Theory
RESTful Rails
Case Study
Authentication
References

REST Theory

REST Introduction
REST is a unifying theory for how “distributed hypermedia” systems are best organized and structured.
Lesson learnt from developers:
CRUD operations correspond to HTTP POST, GET, PUT, and DELETE.
Consistent, robust, and understandable.
Names identifies resources

Resources
A resource is something with identity.
a row in adatabase, a physical object, an abstract concept, or a real-world event in progress
A resource has a URI.
Possible to have more than one???
Different representations of a resource vary based on their content types.
How does the server know which one to send?
URI extensions (/users/1.html,/users/1.xml)
Content negotiation (Accept-Language, Accept-Charset, Accept-Encoding, or Accept)

Resources (example)
GET /orders/124 HTTP/1.1
Host: www.example.com
Accept: text/html, application/xhtml+xml, text/*, image/png, image/*, */*

Embrace hyperlinks
Use hyperlinks to related resources.
Provide a reasonable quantity of information and link to further details.

Statelessness
REST is stateless.
It presents scalibility.
Each request carries no state at lower or higher levels.
Resource state
the internal state that all non trivial resources carry, and it is essential to a web application.
Application state (session state)
the state of the cli-ent’s interaction with the server
keeping this state on the server violates REST principles as it breaks addressability.

HTTP Verbs (HTTP Methods)
Verbs correspond to actions on resources.
GET
HEAD
POST
PUT
DELETE

Safe Methods
Safe methods are used for retrieval.
never be to perform an update
All safe methods are idempotent.

Idempotent Methods
GET, HEAD, PUT, and DELETE are idempotent methods.
The response (and resource state) is the same, no matter how many times thataction is performed.

HTTP Status Codes
Success and failure should be inferred from the HTTP response status
not from an error message within the payload.
1xx: Informational
2xx: Success
3xx: Redirection
4xx: Client Error
5xx: Server Error

GET Method
Transfers a representation of a resource to the client.
Read-only access to a resource.
The server must decide to perform an update based on a safe request.

PUT Method
Updates a resource with the representation provided in the body.
If not exist before, the request creates a new one.

DELETE Method
Deletes the resource identified by its URI.
Subsequent GET queries to the same URI should return a status code of 410 (Gone) or 404 (Not Found).

POST Method
Neither safe nor idempotent
Two primary uses:
creation of new objects
annotation of existing objects
The URI of the POST is that of the object’s container or parent.
The Location header should point to the URI of the created resource

RESTful Rails

Resource-Based Named Routes
Encapsulates all of the Rails CRUD actions into one routing statement
map.resources :users

Custom resource routes
create custom named routes either to the collection (the parent resource) or the members of the collection (the children).
map.resources :people, :collection => { :search => :get }, :member => { :deactivate => :post }

Nested routes
map.resources :people do |person|
person.resources :friends
end
/people/1/friends
/people/1/friends/2
map.resources :people do |person|
person.resources :friends, :name_prefix => 'person_'
end
The name _prefix option adds a prefix to the generated routes.
person_friends_path and person_friend_path

Nested routes (cont.)
map.resources :people
map.resources :friends,
:name_prefix => 'person_',
:path_prefix => '/people/:person_id‘
path_prefix option will add a prefix to the URIs that the route will recognize and generate.

Singleton resource routes
Sometimes, there will be an entity that exists as a singleton.
map.resources :users do |user|
user.resource :account
end
The resource name is still singular, but the inferred controller name is plural.

ActionView Support
The link_to family of helpers can take a :method parameter to define the HTTP method.
generate hidden form field for the _method parameter for PUT and DELETE.
<%= link_to 'Delete', person_path(@person), :method => :delete %>

Content Types
Rails has introduced rich support for rendering different responses based on the content type the client wants, via the respond_to method.
respond_to do |format|
format.html #format.html { render }
format.xml { render :xml => @product }
end
respond_to :html, :xml
In config/initializers/mime_types.rb
Mime::Type.register "image/jpeg", :jpg, [], %w(jpeg)

Content Types (cont.)

Resourceful session state
Alternative to holding session state on the server?
Nearly any problem REST developers face, the solution is to model it as a resource.

Case Study

Example

Refactor

Refactor (example)

Authentication

Authentication
Can we used cookies?
Yes, cookies can be used, but mainly for authentication.
How to authenticate users in a RESTful way via the browser and other clients?

Authentication (cont.)
Use cookies/sessions to store information just for authentication.
Use HTTP Basic authentication for other server side clients.
For more secure, use secure http.

Authentication (cont.)

References
Advanced Rails Recipes
OReilly Advanced Rails
Oreilly RESTful Web Services
http://ajaxpatterns.org/RESTful_Service

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Rest and Rails

by Chamnap Chhorn on Jul 15, 2010

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Rest and Rails — Presentation Transcript