1. REST
Assured
Yaniv Rodenski
Senior Consultant, Sela Group
http://blogs.microsoft.co.il/blogs/roadan
Twitter: @YRodenski

2. A brief history of The Web API
March 2012
ASP.NET is
Open Source
6 Preview Versions
Fab 2012
ASP.NET Web
API (Beta)
October 2010
WCF Web API
on Code Plex

4. State of the web
• Today the web faces new challenges:
– Internet scale applications
– Cloud operating systems

5. State of the web
• Today the web faces new challenges:
– Even more complex integrations

6. State of the web
• Today the web faces new challenges:
– Broader reach of clients

7. Agenda
• Basic terminology
• REST via the ASP.NET Web API
– Richardson maturity model
– Hypermedia Patterns
– Media types
• Caching

8. SOAP
• Promise to add “object access”-like semantics to the
web
– Operation centric
– Uses a large message format
• Extensible
– Over the years a large amount of extending standards
were created (AKA WS-*)
– By extension, adds stateful semantics over the web
• Promotes the use of the proxy pattern
• Not web natural
• Supported by major development environments

9. SOAP Service calls
• Request
• Response

10. HTTP
• Promise to transfer hypertext
• The primal and most native protocol of the
web
• Stateless
• Supported by almost any device on the face of
the earth

11. HTTP Service calls
• Request
• Response

12. SOA
• SOA is an architectural approach for
distributed systems
• SOA defines four tenets focusing on service
autonomy and boundaries
• SOA is a fully mature architecture with well-
known patterns and solutions for complex
communication and integration scenarios

13. REST
• The term Representational State Transfer
(REST) was coined by Roy Fielding in his Ph.D.
thesis in 2000
• An architectural style that embraces HTTP and
the World Wide Web
• Web friendly

14. Richardson maturity model
• Leonard Richardson’s maturity model
describes four levels of service maturity
Hypermedia
Http
Resources

15. RMM – Level zero services
• Level zero services do not use HTTP as an application
protocol.
• Use HTTP as a transport for other remote interaction
mechanism
Hypermedia
Http
Resources

16. RMM – Level one services
• Level one services acknowledge resources
• Resources are accessed via a unique address (formatted as a
Universal Resource Identifier)
• When accessed, a resource returns a representation
http://myfooty.com/players/henrique
http://myfooty.com/players/neymar
Hypermedia
Http
Resources

17. Level one service

18. Web neutrality
• In his famous 2001 bath-tub talk Don Box
drew the line between web pages and web
services by defining their consuming life
forms:
Carbon based Silicon based
Web Pages Web Services

19. RMM – Level two services
• Level two services use HTTP mechanisms
properly:
– Verbs
– Status codes
– Headers
Hypermedia
Http
Resources

20. HTTP verbs
• HTTP defines different methods (sometimes
called verbs) to indicate a desired action to be
performed on a resource
• These verbs define a common terminology
that is accepted by users, developers and the
infrastructure of the World Wide Web

21. Using HTTP verbs for CRUD

22. HTTP status codes
• In addition to a response message, HTTP uses
status codes to communicate to the clients the
resultant status of the operation
• The first digit of the status code specifies one of
five classes of response:
– 1xx Informational
– 2xx Success
– 3xx Redirection
– 4xx Client Error
– 5xx Server Error

23. HTTP headers
• HTTP uses headers to transfer metadata
regarding the message’s content and transport
• HTTP headers are one of HTTP’s main
extensibility points

24. Level Two Service

25. RMM – Level three services
• Level one and two services deal with
resources which represent entities
• Level three services introduce flow
management via hypermedia controls (For
example: links)
Hypermedia
Http
Resources

26. RMM – Level three services
• Hypermedia is used as a logical extension of
the term hypertext in which graphics, audio,
video, plain text and hyperlinks intertwine to
create a generally non-linear medium of
information.
http://en.wikipedia.org/wiki/Hypermedia
Hypermedia
Http
Resources

27. Hypermedia Application

28. Hypermedia Patterns
• Hypermedia can be used to express different
behaviors in an application:
– Control flow management (State machine)
– Discoverability and versioning
– Properties management
– Aspect management
– Paging

29. OData paging

30. Media types (MIME)
• HTTP media types are used to describe the
format of the message body
• In REST media types are used describe
representations, hypermedia controls, and
processing rules
• By creating a media type we can define the
application’s domain

31. Using Media Formatters

32. Cache the REST
• HTTP caches can store copies of the responses
along the request response path to reduce
network traffic
• HTTP caches reduces call latency
• Caches are a main factor for scalability on the
web

33. Types of Cache
• Browser Cache
Stores representations locally on the computer’s hard drive
• Proxy Cache
Corporates and ISPs provide shared proxies providing shared cache
on their network
• Gateway (Reverse Proxy) Cache
Stores representations on behalf of the server. Content Delivery
Networks (CDNs) use gateway cache distributed around the web

34. Controlling Cache
• HTTP headers can be used to control cache
behaviors
• HTTP provides method the avoid staleness of
cached data
– Expiration
– Validation

35. Controlling Cache Behavior

36. Summary
• HTTP is a powerful application level protocol
• Built to serve the worlds largest information
system
• REST provides an architecture that enables
better use of the inherent scaling capabilities of
the web
• Hypermedia enables us to scale and grow our
application

38. My Blog ASP.NET Web APIs
http://bit.ly/roadan http://www.asp.net/web-api/
(best viewed from multiple ip addresses)
Architectural Styles and the Design of HTTP/1.1 Specifications
http://www.w3.org/Protocols/
Network-based Software Architectures
Roy Fielding
http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm
REST in practice (Book)
http://restinpractice.com/default.aspx
Debugging the web with Fiddler
Ido Flatow
http://scc.sela.co.il/SCC/Pages/ShowLecture/ShowLecture.aspx?lectureId=642