REST and Web API

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REST and Web API

Roman Kalita
kalita.roman@gmail.com
@rkregfor
Skype: kalita_roman

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Why we need REST?
Why speak about it?

From web sites to web Apis
From mobile to data

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

Richardson Maturity Model
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Level3: Hypermedia
controls

Level2: HTTP Verbs

Level1: Resources

Level0: POX, Single URI

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

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

Level2
HTTP Verbs

 The system relies on more HTTP verbs and
HTTP response codes on each resource.

doctors/eberwein
GET ?date=…&open=1 Doctor
s
200 OK TimeSlotsList
Client
POST slots/15092012
Slots
204 CREATED ReservationResult

Level3
Hypermedia

 Introduces discoverability, providing a way of making
a protocol more self-documenting.
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

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

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)).)*$" }
);

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) {}
}

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();
}

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

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

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

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

REST and Web API

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