Web Services
Chris McClelland
DevDays, Belfast April 2009
chris@ecliptic-design.com

About
Specialising in Mobile Strategy, Development,
Design and Usability.
New and rapidly developing company based in
Belfast, presently 4 people, but more to come!
Established Jan 2009.

Web Services?
WEB APP
“machine”
API iPhone
reques
t
data

Why?
WEB APP
API
Outsource - community
development
Growth
Novel Use of Data

Success Stories
Google Maps
Last.fm
Ebay
Facebook
Twitter

iPhone Developers Why?
free content
large existing user-base
mashups

@stroughtonsmith

REST vs SOAP

SOAP
Simple Object Access Protocol
XML
SOAP
XML to code and to decode data
SOAP to transport it

REST
REpresentational State Transfer
stateless
just HTTP + URIs
HTTP verbs:
GET: Retrieves a resource
POST: Sends data to create a resource
PUT: Sends data to update a resource
DELETE: Destroys a resource

SOAP
POST /InStock HTTP/1.1
Host: www.example.org
Content-Type: application/soap+xml; charset=utf-8
Content-Length: nnn
<?xml version=\"1.0\"?>
<soap:Envelope
xmlns:soap=\"http://www.w3.org/2001/12/soap-envelope\"
soap:encodingStyle=\"http://www.w3.org/2001/12/soap-
encoding\">
<soap:Body xmlns:m=\"http://www.example.org/stock\">
<m:GetStockPrice>
<m:StockName>IBM</m:StockName>
</m:GetStockPrice>
</soap:Body>
</soap:Envelope>
XML (Extensible Markup Language)

REST
GET www.example.org/user/2

methods URI
POST /user/create
GET /user/show/1
NOT RESTful
POST /user/update/1
POST/GET /user/delete/1
POST /user
GET /user/1
RESTful
PUT /user/1
DELETE /user/1

SOAP
HTTP/1.1 200 OK
Content-Type: application/soap+xml; charset=utf-8
Content-Length: nnn
<?xml version=\"1.0\"?>
<soap:Envelope
xmlns:soap=\"http://www.w3.org/2001/12/soap-envelope\"
soap:encodingStyle=\"http://www.w3.org/2001/12/soap-
encoding\">
<soap:Body xmlns:m=\"http://www.example.org/stock\">
<m:GetStockPriceResponse>
<m:Price>34.5</m:Price>
</m:GetStockPriceResponse>
</soap:Body>
</soap:Envelope>

REST
http://api.flickr.com/services/rest/?
request method=flickr.contacts.getList&api_key=XXX&api_sig=XXX
data <contacts page=\"1\" pages=\"1\" perpage=\"1000\" total=\"3\">
<contact nsid=\"12037949629@N01\"
username=\"Eric\" iconserver=\"1\"
realname=\"Eric Costello\"
friend=\"1\" family=\"0\" ignored=\"1\" />
<contact nsid=\"12037949631@N01\"
username=\"neb\" iconserver=\"1\"
realname=\"Ben Cerveny\"
friend=\"0\" family=\"0\" ignored=\"0\" />
<contact nsid=\"41578656547@N01\"
username=\"cal_abc\" iconserver=\"1\"
realname=\"Cal Henderson\"
friend=\"1\" family=\"1\" ignored=\"0\" />
</contacts>

REST - data received
XML
JSON
RSS, Atom
RSS
PDF
Other e.g. PNG, Microformats

SOAP - benefits
WS-*
offers options for Privacy,
Transfer, Eventing, Addressing,
Notification, ReliableMessaging
Mature
Enterprise

REST Authentication
done via HTTPS
to avoid giving the application / developer your
username and password:
OAuth
“An open protocol to allow secure API
authorisation in a simple and standard method
from desktop and web applications.”

http://www.flickr.com/photos/factoryjoe/

http://www.flickr.com/photos/factoryjoe/

http://www.flickr.com/photos/factoryjoe/

REST - benefits
Simple
Popular, very Web 2.0
Better performance & scalability
Can be cached
Allows diverse formats e.g. JSON
Built into many web frameworks
Easier in Objective-C

iPhone Libraries
HTTP - ASIHTTPRequest
XML, Microformats, RSS, Atom -
NSXMLParser, libxml
JSON - json-framework
Rails - ObjectiveResource
SOAP - wsdl2objc
OAuth - MPOAuthConnection

RESTful APIs
All Yahoo: flickr
myspace, virb, facebook
delicious
Amazon Web Services, SimpleDB
vimeo, youtube
ebay
google

Thanks!
@chrismcclelland
chris@ecliptic-design.com
www.ecliptic-design.com