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REST

RE presentational S tate T ransfer. REST. REST - Theory. Resources Representations Verbs Links Headers HTTP Status Codes. Resources. A resource is identified by a Uri . Uri’s are considered Opaque . http://localhost/api/customers http://localhost/api/customers/1. Representations.

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REST

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  1. REpresentationalState Transfer REST

  2. REST - Theory • Resources • Representations • Verbs • Links • Headers • HTTP Status Codes

  3. Resources • A resource is identified by a Uri. • Uri’s are considered Opaque. http://localhost/api/customers http://localhost/api/customers/1

  4. Representations • Fetching 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>

  5. Verbs • HTTP Verbs are used to operate on resources. • GET must be Side Effect Free • PUT must be Idempotent.

  6. Links • Links 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.

  7. Headers • If-Modified-Since • Etag • Cache-Control • Accept • Content-Type • Authorization

  8. HTTP Status Codes (Just a few...)

  9. Demos • WCF – Building a Simple Rest Service • Linq & REST – ADO.Net Data Services • Entity Framework • Custom classes • MVC meets REST - MonoRail • OAuth – RESTful Authorization

  10. Demo #1 • WCF Demo - A quick tour of a WCF REST service. • webHttpBinding • WebGetvsWebInvoke • UriTemplates • GET, POST, PUT, & Delete • Changing the representation.

  11. 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.

  12. WCF Gotchas • Exceptions 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 fussy • Trailing 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.

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

  14. Entity Framework • Using 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 Service • Edit 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); }

  15. Querying -Simple

  16. Querying – Advanced

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

  18. Implementation

  19. ADO.Net Data Entities - Client • Entities 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).

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