Building RESTful Services using WCF

Jon Flandershttp://www.rest-ful.net/INT303

About Me Jon Flanders –

http://www.rest-ful.net/

Independent consultant/trainer

BizTalk MVP

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Storytime: Once upon time…

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REST

Representational State Transferintroduced by Roy Fielding

Architectural styleA set of constraints distilled from the architecture of the Web

URIs represent resourcesClients interact via with resources via a uniform interface (GET, POST, PUT, DELETE)Services are stateless

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Why should you care?

Microsoft Live Services .NET Services

ADO.NET Data Services

EVERYBODY that isn’t Microsoft (Twitter,Google,

Yahoo, Facebook, MySpace)

More to come from Microsoft and others – but why let them have all the

fun (and rewards)?

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REST Advantages

GET responses can be cachedUsing URIs build on experience using the WebUniform interface simplifies building and using servicesStatelessness constraint eases scalabilityGET is safe, can be called N times without causing changePUT and DELETE are idempotent (same effect no matter how many times called)

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Building a RESTful service

Design your resource(s)Determine the URI for each resourceDetermine what part of the uniform interface each resource should implement

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Uniform Interface

•Retrieves a resource

•Guaranteed not to cause side-effects (SAFE)

•Results are cacheable

GET

•Creates a new resource

•Unsafe: effect of this verb isn’t defined by HTTP

POST

•Updates an existing resource

•Used for resource creation when client knows URI

•Can call N times, same thing will always happen (idempotent)

PUT

•Removes a resource

•Can call N times, same thing will always happen (idempotent)

DELETE

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Windows Communication Foundation (WCF)

Framework for building applications that communicate

Client-ServerMessage orientedService oriented

WCF abstracts away network complexities, developer concentrates on codeMost of WCF is highly geared toward SOAPREST support added in 3.5 and improved in 3.5 sp1

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WCF Messages to Methods

In WCF developers write methods in classes that respond to network messagesSOAP support in 3.0/3.5 routes messages to methods based on SOAP Action

URI always the sameAlways uses POST

Done by the default dispatcher

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WCF 3.5 Web Programming

Messages are routed to methods based on:URIHTTP Verb

Same programming model as “SOAP”ServiceContract, OperationContract, DataContract

New dispatcher that maps URIs/Verbs to methods

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WCF 3.5 REST infrastructureUriTemplate & UriTemplateTable

URI parsing WebGet & WebInvoke attributes

UriTemplate defines URI WebGet + UriTemplate maps GET requests to methodsWebInvoke + UriTemplate maps remainder of uniform interface to methods , Method property determines verb (POST is default)

WebHttpBinding/WebServiceHost/WebServiceHostFactory

Eases use and configuration

WCF Dispatching

Network

Message

Transport Channel

Message Encoder

Protocol Channel (1-N)

Your Code

Dispatcher(Action)

Dispatcher(URI + VERB)

Transport Channel(HTTP)

Message Encoder(Text + No SOAP)

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AJAX Support

Many RESTful clients are JavaScript based AJAX clientsJavaScript Object Notation (JSON) is the preferred resource representation

Smaller footprint than XMLNo parsing necessary

WCF has support for AJAX applications at two levels

JSONDataContractSerializer for JSON parsing and generationJavaScript “proxy” build on ASP.NET AJAX

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Web Feeds

Web Feeds are endpoints that expose machine consumable resource representations

Commonly used for web logs (blogs), news etc.Expansion into enterprise data is happening

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WCF support for Feeds

Built on top of WCF REST support (WebGet/UriTemplate)Feed specific feature is feed-format neutral object model

Transform your data into the WCF OMOM serialized to either RSS or Atom (or other future formats – extensible formatting capabilities)OM is closer to Atom model (Atom is richer than RSS)

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Know the rules, bend when necessary

“…REST isn’t an all or nothing proposition. One can get significant value from partial adoption. “ Sam Ruby - Author RESTFul Web Services

Don’t underestimate the power of GET!

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Summary

REST is an architectural style that encourages interoperable, scalable web servicesBuilds on the existing architecture of the webWCF 3.5 adds support for this architecture

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© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS,

IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.