Why we need REST? Why speak about it? Roman Kalita

1. I
REST and Web API
Roman Kalita
kalita.roman@gmail.com
@rkregfor
Skype: kalita_roman

2. I
Why we need REST?
Why speak about it?

4. From web sites to web Apis
From mobile to data

5. Representational
State
Transfer
 Architectural style
based on HTTP protocol usage and
principles of The Web
 Tightly coupled to HTTP protocol
 Lightweight
 Stateless
 Simple caching “from the box”
 Easy to consume (e.g. mobile devices, JavaScript etc.)
 Goal: scaling, loose coupling and
compose functionality across service boundaries

6. Richardson Maturity Model
I
Level3: Hypermedia
controls
Level2: HTTP Verbs
Level1: Resources
Level0: POX, Single URI

7. Level0
POX, Single URI, Transport
 The systems focus are service end point URI and
one HTTP verb (likely POST verb) for communication.
AppointmentService
GetOpenTimeSlot
TimeSlotsList
Servic
Client
e
MakeAppointment
ReservationResult

8. Level1
Resources
 Introduces resources, URIs per resource, but one HTTP ve
 Handling complexity by using divide and conquer,
breaking a large endpoint down into multiple resources.
http://klinik.com/
POST doctors/eberwein Doctor
s
TimeSlotsList
Client
POST slots/15092012
Slots
ReservationResult

9. Level2
HTTP Verbs
 The system relies on more HTTP verbs and
HTTP response codes on each resource.
http://klinik.com/
doctors/eberwein
GET ?date=…&open=1 Doctor
s
200 OK TimeSlotsList
Client
POST slots/15092012
Slots
204 CREATED ReservationResult

10. Level3
Hypermedia
 Introduces discoverability, providing a way of making
a protocol more self-documenting.
http://klinik.com/
doctors/eberwein
GET ?date=…&open=1 Doctor
200 OK TimeSlotsList
s
<link rel = "/linkrels/slot/book"
Client uri = "/slots/5678"/>
POST slots/15092012 Slots
204 CREATED ReservationResult

11. Cooking REST on .NET –
Web API
 URL Routing to produce clean URLs
 Content Negotiation based on Accept headers
for request and response serialization
 Support for a host of supported output formats
including JSON, XML, ATOM
 Extensible (easy to add new formats, custom handlers,
routing, error handlers)
 Self-hostable in non-Web applications
 Testable using testing concepts similar to MVC

12. Web API Routing
 Routing “à la” ASP.NET MVC
 Register your routs from Application_Start in Global.asax.cs
RouteTable.Routes.MapHttpRoute(
name: "UploadDownlaodOnlyTrhougthTransport",
routeTemplate: "api/transports/{controller}/{id}",
defaults: new { id = RouteParameter.Optional },
constraints: new { controller = "uploads|downloads" }
);
RouteTable.Routes.MapHttpRoute(
name: "AllExceptUploadaDownload",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional },
constraints:
new { controller = @"^((?!(downloads|uploads)).)*$" }
);

13. Web API Controller
 Derived from ApiController
 Actions are mapped to URIs
via naming convention or attributes
 Deep support for more advanced HTTP features
via HttpResponseMessage and HttpRequestMessage.
public class ProductsController : ApiController
{
public IEnumerable<Product> GetAllProducts(){}
public Product GetProduct(int id) {}
public HttpResponseMessage PostProduct(Product item) {}
public void PutProduct(int id, Product contact) {}
[AcceptVerbs("GET", "HEAD")]
public Product FindProduct(id) {}
[HttpGet]
public Product FindProduct(id) {}
}

14. OData support
 Support “in the box” for OData $top, $skip, $filter, $orderby,
advanced support in pre-release
Install-Package Microsoft.AspNet.WebApi.OData -Pre
Till release - as alternative use of WCF Data Services
 Queryable attribute to enable OData queries
http://localhost:38856/api/products?$filter=category+eq+'Toys'
[Queryable]
public IQueryable<Product> GetAllProducts()
{
return repository.GetAll().AsQueryable();
}

15. Web API extensiblity
 Message handlers
to handle request and responses
 Action filters
for custom logic before and after action execution
 Custom formatters
to add custom media type formats
 Dependency resolver
to enable dependency injection for controllers

16. Things that help
HTTP debugging proxies
 Fiddler
fiddler2.com
 Curl, for cmd-line fans
curl.haxx.se
 Httpie, for cmd-line fans
github.com/jkbr/httpie
Debugging
 Wireshark
 Remote debug
Service things
 REST service help page
 Test web client

17. Read more and references
 RFCs ietf.org/rfc/... URI …/rfc3986.txt,
URL …/rfc1738.txt HTTP, …/rfc2616.txt
 Web API bloggers
 webapibloggers.com
 ASP.NET Web API
 asp.net/webapi
 aspnetwebstack.codeplex.com
 Alternatives to Web API
 servicestack.net
 Martin Fowler’s article about Richardson Maturity Model
 martinfowler.com/articles/richardsonMaturityModel.ht
ml

18. http://www.flickr.com/photos/f-oxymoron/5005673112