RESTREpresentationalState Transfer

REST - TheoryResources RepresentationsVerbsLinksHeadersHTTP Status Codes

ResourcesA resource is identified by a Uri.Uri’s are considered Opaque.http://localhost/api/customershttp://localhost/api/customers/1

RepresentationsFetching a resource returns a Representation.Representations have a content type i.e. text/xml, application/json, text/html etc.<customer> <self>http://localhost/api.svc/customers/12</self> <organisation>DevDefined</organisation> <id>1</id> <orders>http://localhost/api.svc/customers/12/orders </orders></customer>

VerbsHTTP Verbs are used to operate on resources.GET must be Side Effect FreePUT must be Idempotent.

HTTP Verbs are used to operate on resources.

GET must be Side Effect Free

PUT must be Idempotent.

LinksLinks are returned in representations.Clients follow links, allowing them to transition state.Using Links can provide elegant ways to scale out or integrate 3rd party services.

HeadersIf-Modified-SinceEtagCache-ControlAcceptContent-TypeAuthorization

HTTP Status Codes (Just a few...)

DemosWCF – Building a Simple Rest ServiceLinq & REST – ADO.Net Data ServicesEntity FrameworkCustom classesMVC meets REST - MonoRailOAuth – RESTful Authorization

Demo #1WCF Demo - A quick tour of a WCF REST service.webHttpBindingWebGetvsWebInvokeUriTemplatesGET, POST, PUT, & DeleteChanging the representation.

Fresh to Fiddler?Fiddler is very useful when developing REST services.There are some catches for first time users:Disable IPV6 in Fiddler when using Cassini (it doesn’t like the ::1 loopback address)Use “.” after localhost when testing with IE 7 to stop proxy being bypassed.i.e. http://localhost.:8080/api.svc/customers/FireFox users - you need to manually configure proxy settings.

WCF GotchasExceptions end up as 500 errors on client. You need to explicitly set status for non-server errors (i.e. For invalid requests)Uri Templates are fussyTrailing slashes will cause a match to fail, contrary to many peoples expectations.HTTP Method names are case-sensitive.Using “Post” instead of “POST” can make for confusing 405 errors The input/output Representation format is defined at the contract operation level.Targeting multiple representations “across the board” is ugly.Support for linking resources is non-existent.

Demo #2ADO.Net Data Services (Was Astoria)Building Service using ADO.Net Entity Framework.Exploring Query Syntax.

Entity FrameworkUsing EF - Out of scope However... Provides easy way to quickly play with Astoria.Add Item -> Entity Model Use AdventureWorks database, just the tables should do, call it “AdventureWorks”Add Item -> ADO.Net Data ServiceEdit the .cs file, set entities class for service to AdventureWorksModel.AdventureWorksEntities.Alter InitializeService method to look like this(Don’t do this for production use)public static void InitializeService(IDataServiceConfigurationconfig){config.SetEntitySetAccessRule("*", EntitySetRights.All);config.SetServiceOperationAccessRule("*", ServiceOperationRights.All);}

Querying -Simple

Querying – Advanced

Custom Objects – Demo #3ADO.Net Data Services isn’t limited to the EF.Anything implementing IQueryable interface will work too.Let’s try!

Implementation

ADO.Net Data Entities - ClientEntities comes with a .Net Client.Found in the System.Data.Services.Client assembly.Client allows Linq -> Uri -> Linq -> Whatever.With different Types on the client and Server!Client types can be POCO objects, even if the server side representations are not.[DataServiceKey(...)] attribute required to support non-GET requests.Client implements a “unit of work” like pattern, allowing changes to be collected and then persisted at once.Changes can be batched in a single request (though this can be viewed as a perversion of HTTP principles).