WCF 3.5, REST ET AL. HOW TO?Adnan Masood

www.AdnanMasood.com

ABOUT MEAKA. SHAMELESS SELF PROMOTION

• Sr. Software Engineer / Tech Lead for Green Dot Corp. (Financial Institution)

• Design and Develop Connected Systems• Involved with SoCal Dev community, co-founded San Gabriel

Valley .NET Developers Group. Published author and speaker.• MS. Computer Science, MCPD (Enterprise Developer), MCT,

MCSD.NET• Doctoral Student - Areas of Interest: Machine learning, Bayesian

Inference, Data Mining, Collaborative Filtering, Recommender Systems.

• Contact at adnanmasood@acm.org• Read my Blog at www.AdnanMasood.com• Doing a session in IASA 2008 in San Francisco on Aspect Oriented

Programming; for details visit http://www.iasaconnections.com

AGENDA

Overview of SOA, Web Services, Design Patterns

What’s new in WCF 3.5 Discuss what is REST? How to Implement REST using WCF? What are UriTemplates? How to use them in .NET 3.5?

ARCHITECT IQ TEST

What are the four tenants of SOA?

TENANTS OF SOA

1. Boundaries are explicit 2. Services are Autonomous 3. Services share Schema and Contract, not

Class 4. Compatibility is based upon Policy

ABBR./ACRONYMS 101

• REST • SOAP • JSON • POX • RSS• ATOM

• Representational State Transfer

• Simple Object Access Protocol• Javascript Object Notation• Plain Old XML• Really Simple Syndication

WHAT IS REST?

• REST is a term coined by Roy Fielding in his Ph.D dissertation [1] to describe an architecture style of networked systems.

[1] http://www.ebuilt.com/fielding/pubs/dissertation/top.htm

REST

Representational State Transfer

There are REST-Services and “REST-like” services which use XML and HTTP but not the underlying philosophy of REST

REST outlines the philosophy of mapping HTTP verbs to the Create/Retrieve/Update/Delete philosophy of APIs as discussed in a PhD thesis by Roy Fielding

• http://example.com/users/ http://example.com/users/{user} (one for each user) http://example.com/findUserForm http://example.com/locations/ http://example.com/locations/{location} (one for each location) http://example.com/findLocationForm

Examples

WCF SUPPORT TO REST

WebHttpBinding: Sends information directly over HTTP or HTTPS—no SOAP envelope is created. This binding is new with the .NET Framework 3.5 version of WCF, and it’s the right choice for RESTful communication and other situations where SOAP isn’t required. The binding offers three options for representing content: text-based XML encoding, JavaScript Object Notation (JSON) encoding, and opaque binary encoding.

“REPRESENTATION STATE TRANSFER” IS THE IDEA BEHIND RESOURCE ORIENTED ARCHITECTURE

ResourceClienthttp://www.myblog.com/{year}/{month}/{day}

Posts 01012008 – a view and not a physical file

The Client references a Web resource using a URL. A representation of the resource is returned which can be rendered as an HTML.

Blog Posts for the day

MOTIVATION FOR REST

"The motivation for developing REST was to create an architectural model for how the Web should work, such that it could serve as the guiding framework for the Web protocol standards.

REST has been applied to describe the desired Web architecture, help identify existing problems, compare alternative solutions, and ensure that protocol extensions would not violate the core constraints that make the Web successful."

- Roy Fielding

REST VS. SOAP

– Enhanced Caching – Invocation vs. Resource– Bloat vs. Simplicity– Proxy Servers –Web evolution (semantic Web)– Generic Uri based interface via

UriTemplates (versus custom SOAP interface)

– Interoperability

RESTFUL ARCHITECTURE BEST PRACTICES*

1. Prefer HTTP-GET over POST when a information resource URI is exposed.

2. Publish a logical URI for every programmable resource being exposed in the service.

3. Logical URI are preferred over the physical URL. The logical URL (such as : http://www.myblog.com/2008/7/2/) is better than physical URI. (http://www.myblog.com/20080702.html)

4. Create and Follow URI Template rules; this way logical URIs can modify the implementation without impacting client applications.

5. REST services focus on representing resources as "things" and not "actions". The REST Uri’s are the nouns, not verbs.

*Roger L. Costello XML technologies course also discusses some of these points.

RESTFUL ARCHITECTURE BEST PRACTICES (CONT.)

6. Design functional oriented read methods i.e. the GET methods should be side-effect free.

7. Use the extended information links in the responses to allow the consuming application to follow the next steps if further actions are needed.

8. As a corollary to item 6, use the extended information links for workflow actions to allow the atomic unfolding based on the current state.

9. Meaningful Uri templates are more effective than Query strings; for instance http://www.myblog.com/2008/7/2/ is more appropriate REST pattern than http://www.myblog.com/page.aspx?pageid=20080702)

10. The URL delimiter “/” should be used to represent the inheritance or “part of” relationship in the logical hierarchy. For instance http://www.myblog.com/{year}/{month}/{day}/ is more effective than http://www.myblog.com/{day}/{month}/{year}.

QUESTIONS

• HTTP Programming with WCF and the .NET Framework 3.5 - Justin Smithhttp://msdn.microsoft.com/msdnmag/issues/08/01/WCFinOrcas/default.aspx

• What's New for WCF in Visual Studio 2008 – Juval Lowy http://msdn.microsoft.com/msdnmag/issues/08/02/Foundations/default.aspx

• RESTful Web Services By Leonard Richardson, Sam Rubyhttp://www.amazon.com/RESTful-Web-Services-Leonard-Richardson/dp/0596529260

• Mix 2007 Talk by Don Box and Steve Maine “DEV03 - Navigating the Programmable Web” http://sessions.visitmix.com/default.asp?event=1011&session=2012&pid=DEV03&disc=&id=1512&year=2007&search=DEV03

REFERENCES

REFERENCES• Paul Prescod has written several excellent articles on REST:

– Second Generation Web Services• http://www.xml.com/pub/a/2002/02/06/rest.html

– REST and the Real World• http://www.xml.com/pub/a/2002/02/20/rest.html

– SOAP, REST and Interoperability• http://www.prescod.net/rest/standardization.html

– Evaluating XML for Protocol Control Data• http://www.prescod.net/xml/envelopes/

• Wikipedia Entry on REST• http://en.wikipedia.org/wiki/Representational_State_Transfer

• Publishing RSS and ATOM Feeds using WCF 3.5 Syndication Libraries• http://www.codeproject.com/KB/WCF/WCF35RSSATOM.aspx

• Exploring WCF 3.5 Tools - WcfSvcHost and WcfTestClient• http://www.codeproject.com/KB/WCF/WCF35Utils.aspx

• Web Service Studio• http://www.codeplex.com/WebserviceStudio

• JSON • http://en.wikipedia.org/wiki/JSON

CONCLUDING REMARKS

REST is a “new” paradigm for .NET Developers; a new way to think about programming web services but it’s not really new since we have been using it for a long time over the web.

Any Questions / Comments … feel free to contact adnanmasood@gmail.com

Visit www.AdnanMasood.com