REST AND RAILS

Chhorn ChamnapYoolkMango

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.comAccept: 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 serverkeeping 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 statusnot 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 objectsannotation 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 statementmap.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 routesmap.resources :people do |person|

person.resources :friendsend /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 :peoplemap.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.rbMime::Type.register "image/jpeg", :jpg, [], %w(jpeg)

Content Types (cont.)

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)

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.)

Authentication (cont.)

References

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