A quick overview on REST : what it is and what it is not. REST has strict contraints and many internet Apis are not so REST. It’s also very popular today because RESTfull services can be consumed easily by any client or device. Soap is also still valid in a few circomstaces. It has never been so easy to create Rest-like services in .net since asp.net Web Api.

1. LET’S HAVE A REST !
MAXIME LEMAITRE - 11/04/2013
Private and Confidential

2. Agenda
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Introduction
What it is not, what it is
REST constraints
In the web Industry
SOAP Vs REST
REST-style Service in .NET
Conclusion

3. REST
a vastly misunderstood term
• REpresentational State Transfer is not a
– Philosophy essay
– Language
– Protocol
– Standard, RFC
– Framework of MS, Google, Facebook, …
– Technology
–…

4. REST
what REST is
• Introduced in 2000 by Roy Fielding
– principal author of HTTP and creator of Apache Web Server
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REST is an architecture style
– a coordinated set of architectural constraints that restricts the roles and
features of architectural elements, and the allowed relationships between
those elements
• Client–server
• Stateless
• Cacheable
• Layered system
• Uniform interface
• Code on demand (optional)
Conforming to these constraints is referred to as being RESTful

5. REST
Constraints
Client – Server
Stateless
“No restrictions on the nature of the
client, on the number of the clients
and on communication medium /
protocol”
“... each request from client to server
must contain all of the information
necessary to understand the
request, and cannot take advantage
of any stored context on the
server, independent of any requests
that may have preceded it »
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Separate data storage concerns
Improve user interface portability
across multiple platforms
Improve scalability by simplifying
server components
Components evolve independently
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Session state is kept on client
Improved visibility because every
exchange is self descriptive
Easier recoverability from partial
failures
Improved scalability on server

6. REST
Constraints
Cacheability
“... the data within a response to a
request must be implicitly or
explicitly labeled as cacheable or
non-cacheable. If a response is
cacheable, then a client cache is
given the right to reuse that response
data for later, equivalent requests.”
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Reduces client to server interactions
Improves efficiency, scalability and
user perceived performance
Layered System
“The layered system style or also
popularly referred to as n-layer
system allows an architecture to be
composed of hierarchical layers by
constraining component behavior
such that each component cannot
"see" beyond the immediate layer
with which they are interacting.”

7. REST
Constraint : Uniform Interface
Information is transferred in a standardized form
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Considered fundamental to the design of any REST app
Identification of resources
Each resource has a URI and is access through a defined set of HTTP methods
(GET, PUT, POST, DELETE)
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Manipulation of resources through representations
Each resource can have one or more representations. Such as
application/xml, application/json, text/html, etc. Clients and servers negotiate to select
representation.
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Self-descriptive messages
Requests and responses contain not only data but additional headers describing how the
content should be handled. Such as if it should be cached, authentication requirements, etc.
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Hypermedia as the engine of application state (aka HATEOAS)
Clients make state transitions only through actions that are dynamically identified within
hypermedia by the server (e.g., by hyperlinks within hypertext). Except for simple fixed
entry points to the application, a client does not assume that any particular action is
available for any particular resources beyond those described in representations previously
received from the server.

8. REST
big brother
What is the biggest known RESTful
System on planet Earth?
World Wide Web

9. RESTful Web Service
REST for the web
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A RESTful web API (also called a RESTful web service) is a web API implemented
using HTTP and the principles of REST
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URI (Clean ?)
Internet media types
HTTP Headers
HTTP Response Codes
HTTP Methods
• GET
• POST
• PUT
• DELETE
…
RESTful Web Service uses the existing features of the HTTP protocol.
Layered proxy and gateway components perform additional functions on the
network, such as HTTP caching and security enforcement.

10. REST
in the web industry
• Definition of REST lost its way when popular services emerged
calling themselves REST which were not
– Having an HTTP server accept GET requests or POST and responding
with XML, JSON or some other data format
is not automatically RESTful
• Not so many RESTful services, but many REST-like services
and web Api ( loose adherence)
– Client scripts
– Exposed Operations

11. REST
what makes REST-style web services so popular today ?
• Because it’s based on the same constraints that make the
Web successful
– Web was not designed as an Xml Bus with RPC
• Since it uses standard HTTP features, it is much more
simpler, easier, faster and scalable than any other web
technology
• REST-styles permits many different data formats (json, xml, …)
• REST-styles web services can be consumed easily by any
client or device
– Do you know a better way to touch
desktop browsers, mobile, tablets
for any OS or technology ?

12. REST vs SOAP
SOAP web service
REST-style web service
Support multiple transport protocols (HTTP, TCP, UDP, and HTTP only and more suitable for access from various
custom transports)
browsers, mobile devices etc enabling wide reach.
Enables building services that support multiple encodings
(Text, MTOM, and Binary) of the same message type and
allows switching between them.
Enables building Web APIs that support wide variety of
media types including XML, JSON etc.
Supports building services with WS-* standards like
Reliable Messaging, Transactions, Message Security.
Uses basic protocol and formats such as HTTP,
WebSockets, SSL, JQuery, JSON, and XML. There is no
support for higher level protocols such as Reliable
Messaging or Transactions.
Supports Request-Reply, One Way, and Duplex message
exchange patterns.
HTTP is request/response but additional patterns can be
supported through SignalRand WebSockets integration.
WCF SOAP services can be described in WSDL allowing
automated tools to generate client proxies even for
services with complex schemas.
There is a variety of ways to describe a Web API ranging
from auto-generated HTML help page describing snippets
to structured metadata for OData integrated APIs.

13. REST
How to build a REST-style Service in .NET ?
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Using WCF (deprecated)
– Using WebHttpBinding & WebHttpBehavior
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Using Asp.net Web Api
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Not part of .NET, open-source as MVC
Strong Support URL Routing to produce clean URLs using familiar MVC style semantics
Content Negotiation based on Accept headers for request and response serialization
Support for a host of supported output formats including JSON, XML, ATOM
Strong default support for REST semantics but they are optional
Easily extensible Formatter support to add new input/output types
Convention based design that drives you into doing the right thing for HTTP Services
Very extensible, based on MVC like extensibility model of Formatters and Filters
Self-hostable in non-Web applications
Testable using testing concepts similar to MVC
…

14. REST
How to build a REST-style Service in .NET ?
/api/products/2

15. Conclusion
• REST is a vastly misunderstood term
• REST-styles web services are very popular today because they
are simple, easy to use, performant , scalable and can be
consumed by any client
• REST-style Vs SOAP ? Both the REST-style and SOAP have
advantages and disadvantages when it comes to building
services. It’s more related to an architectural Decision.
to rest ...

16. Appendices
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http://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm
http://kellabyte.com/2011/09/04/clarifying-rest/
http://www.asp.net/web-api
http://msdn.microsoft.com/en-us/library/dd203052.aspx
http://msdn.microsoft.com/en-us/magazine/dd942839.aspx
http://rest.elkstein.org/2008/02/what-is-rest.html
http://proceedings.esri.com/library/userconf/devsummit09/papers/keynote_chap
pell.pdf

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