You Look Like You Could Use Some REST!

You Look Like You
Could Use Some REST!

Ben Ramsey ■ php|works PyWorks ■ 13 November 2008

Roatan Beach - Perfect Day, by Janusz Leszczynski

REST

Is it about
pretty URLs?

Tom Coates, by Patrick Lauke

#webdevgangsign

How about XML
over HTTP?
Web Developer Gang Sign, by Josh Lewis

Any web service that’s
not SOAP?

A Bar of Ivory Soap, by iirraa

Representational
State TransferRestful Summer, by Clear Inner Vision

Public Domain, from Wikimedia Commons

Theory
of REST

REST defines a style by
which a resource’s state
may be transferred using
a representation of that
resource.

Resources

Back on the Log Train, by Claire L. Evans

Addressable

Address:1304, by Grant Hutchinson

Uniform
Interface
used to interface, by Tom Hensel

Client-server
Stateless
Cacheable
Layered
Separated, by Hansol Lee

RESTful Benefits

Improved response time & reduced
server load
Improves server scalability
Requires less client-side software
Depends less on vendor software
No need for resource discovery
Better long-term compatibility &
evolvability than RPC
Sand Banks Sunset, by Clear Inner Vision

A Real-World
Analogy
Money!, by Tracy Olson

RESTful
Practice

Public Domain, from Wikimedia Commons

“[REST] is intended to evoke an image
of how a well-designed Web
application behaves: a network of web
pages (a virtual state-machine), where
the user progresses through an
application by selecting links (state
transitions), resulting in the next page
(representing the next state of the
application) being transferred to the
user and rendered for their use.”
— Roy Fielding

Drip Drops and the Spider Web, by Mike Bitzenhofer

Hypertext
Transfer
Protocol
URIs provide unique addresses
Constrained interface with methods
and content types
Transactions are atomic
Built-in support for layering
Provides for cache control
#110 Hypertext Transfer Protocol, by maako

HTTP Interface

Methods Cut & Paste

GET Copy
PUT Paste Over
POST Paste After
DELETE Cut


HTTP Interface
GET

Transfers (copies) a representation of a
resource from server to client
Body must contain enough information
for the client to usefully operate on the
data
Considered safe
Has the property of idempotence

HTTP Interface
PUT

Transfers the state from client to the
server (equivalent to paste over)
The body must contain enough
information for the server to operate
on the data
May also create a new resource at the
requested URI

HTTP Interface
POST

Has the same meaning as paste after
May create or update resources,
depending on context
Is not idempotent


HTTP Interface
DELETE

Acts like cut
Requests that the resource identified
be destroyed or removed from public
web


Idempotence

Not a sexual dysfunction
The side-effects of N > 0 identical
requests is the same as for a single
request
That is: every time you make the
request, as long as it is an identical
request, exactly the same action
occurs

Content Types

HTTP supports content types through
the Content-Type header
A single resource can be transferred in
various content types
Content negotiation used to tell the
server what type to return to the client
REST community doesn’t care for
content negotiation

Lifecycle of a Resource

1

POST /content HTTP/1.1
Host: example.org
Content-Type: application/xml

2

HTTP/1.x 201 Created
Date: Thu, 13 November 2008 16:43:56 GMT
Location: /content/1234



3

GET /content/1234 HTTP/1.1
Host: example.org

4

HTTP/1.x 200 OK



5

PUT /content/1234 HTTP/1.1
Host: example.org

6

HTTP/1.x 200 OK



7

DELETE /content/1234 HTTP/1.1
Host: example.org

8

HTTP/1.x 204 No Content


Resource-oriented
Architecture
1. Represent itself to the client
2. Transition from one state to the next
3. Destroy itself

Additionally, the system knows how to
create a resource.

Where I Teach, by Todd Ehlers

Resource-oriented
Architecture
Resources are addressable
Resources have no state
Resources are connected
Resources share the same interface


Resource-oriented
Architecture
Query string parameters appropriate
in some cases
Pragmatic use of URIs instead of
using HTTP headers
RPC-style APIs are avoided
Representation should have links
URI templates specify URI families

Resource-oriented
Architecture
Should expose many URIs
Session cookies are not RESTful
Combined resources are RESTful only
if represented as a URI
URIs should facilitate “cut & paste”


Atom
A resource-oriented protocol for
publishing documents that sits on top
of HTTP

Molecule display, by Christian Guthier

Atom
Entry Document
application/atom+xml;type=entry
Feed (Collection) Document
application/atom+xml;type=feed
Category Document
application/atomcat+xml
Service Document
application/atomsvc+xml


Atom Resource Lifecycle

1

GET /index.atom HTTP/1.1
Host: example.org

2

HTTP/1.x 200 OK
Content-Type: application/atomsvc+xml



3

GET /archives.atom HTTP/1.1
Host: example.org

4

HTTP/1.x 200 OK
Content-Type: application/atom+xml;type=feed



5

GET /categories.atom HTTP/1.1
Host: example.org

6

HTTP/1.x 200 OK
Content-Type: application/atomcat+xml



7

POST /archives.atom HTTP/1.1
Host: example.org
Content-Type: application/atom+xml;type=entry

8

HTTP/1.x 201 Created
Location: /archives/1234.atom



9

GET /archives/1234.atom HTTP/1.1
Host: example.org

10

HTTP/1.x 200 OK



11

PUT /archives/1234.atom HTTP/1.1
Host: example.org

12

HTTP/1.x 200 OK



13

DELETE /archives/1234.atom HTTP/1.1
Host: example.org

14

HTTP/1.x 204 No Content


RESTful
Design
1. Determine your resources

User Content
/users /content
/users/{username} /content/{ID}

Before we had CAD, we had Lead!, by Wendell

RESTful
Design
2. Decide the methods for each
resource

/users /users/{username} /content /content/{ID}
GET GET GET GET
POST PUT POST PUT
DELETE DELETE


RESTful
Design
3. Connect your resources


RESTful
Design
4. Determine your data schemas


RESTful
Design
5. Choose your content type(s)


In Conclusion...

It’s all about resources.

Conclusion, by Mark Cummins

There’s More To Learn

Authentication
Digital signing
Encryption
WSDL 2.0 & WADL

You Look Like You Could Use Some REST!

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