Rest and Rails

REST And railsChhorn ChamnapYoolkMango15 - July - 2010

AgendaREST TheoryRESTful RailsCase StudyAuthenticationReferences

REST IntroductionREST 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

ResourcesA resource is something with identity.a row in adatabase, a physical object, an abstract concept, or a real-world event in progressA 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.

StatelessnessREST is stateless.It presents scalibility.Each request carries no state at lower or higher levels.Resource statethe 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.GETHEADPOSTPUTDELETE

Safe MethodsSafe methods are used for retrieval.never be to perform an updateAll safe methods are idempotent.

Idempotent MethodsGET, 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 CodesSuccess and failure should be inferred from the HTTP response statusnot from an error message within the payload.1xx: Informational2xx: Success3xx: Redirection4xx: Client Error5xx: Server Error

GET MethodTransfers 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 MethodUpdates a resource with the representation provided in the body.If not exist before, the request creates a new one.

DELETE MethodDeletes 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 MethodNeither safe nor idempotentTwo primary uses:creation of new objectsannotation of existing objectsThe 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

Resource-Based Named RoutesEncapsulates all of the Rails CRUD actions into one routing statementmap.resources :users

Custom resource routescreate 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/2map.resources :people do |person| person.resources :friends, :name_prefix => 'person_'endThe 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 routesSometimes, there will be an entity that exists as a singleton.map.resources :users do |user| user.resource :accountendThe resource name is still singular, but the inferred controller name is plural.

ActionView SupportThe 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 TypesRails 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 }endrespond_to :html, :xmlIn config/initializers/mime_types.rbMime::Type.register "image/jpeg", :jpg, [], %w(jpeg)

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

AuthenticationCan 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.

ReferencesAdvanced Rails RecipesOReilly Advanced RailsOreilly RESTful Web Serviceshttp://ajaxpatterns.org/RESTful_Service

Rest and Rails

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