Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)
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Transcript of Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)
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David Zuelke
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David Zülke
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http://en.wikipedia.org/wiki/File:München_Panorama.JPG
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Founder
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Lead Developer
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THE OLDEN DAYSBefore REST was En Vogue
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http://www.acme.com/index.php?action=zomg&page=lol
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along came
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dis is srs SEO bsns
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and said
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NEIN NEIN NEIN NEIN
DAS IST VERBOTEN
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at least if they were
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so we had to make URLs "SEO friendly"
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http://www.acme.com/zomg/lol
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and then things got out of control
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because nobody really had a clue
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http://acme.com/videos/latest/hamburgers
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http://acme.com/search/lolcats/pictures/yes/1/200
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oh dear…
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THE RISE OF WEB SERVICESOhai, I'm ur CEO, I canhaz SOAP API plz, today, kthx?
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POST /soapendpoint.php HTTP/1.1Host: localhostContent-‐Type: text/xml; charset=utf-‐8
<?xml version="1.0" encoding="UTF-‐8"?><SOAP-‐ENV:Envelope xmlns:SOAP-‐ENV="http://schemas.xmlsoap.org/soap/envelope/"> <SOAP-‐ENV:Body> <ns1:getProduct xmlns:ns1="http://agavi.org/sampleapp"> <id>123456</id> </ns1:getProduct> </SOAP-‐ENV:Body></SOAP-‐ENV:Envelope>
HTTP/1.1 200 OKContent-‐Type: text/xml; charset=utf-‐8
<?xml version="1.0" encoding="UTF-‐8"?><SOAP-‐ENV:Envelope xmlns:SOAP-‐ENV="http://schemas.xmlsoap.org/soap/envelope/"> <SOAP-‐ENV:Body> <ns1:getProductResponse xmlns:ns1="http://agavi.org/sampleapp"> <product> <id>123456</id> <name>Red Stapler</name> <price>3.14</price> </product> </ns1:getProductResponse> </SOAP-‐ENV:Body></SOAP-‐ENV:Envelope>
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POST /soapendpoint.php HTTP/1.1Host: localhostContent-‐Type: text/xml; charset=utf-‐8
<?xml version="1.0" encoding="UTF-‐8"?><SOAP-‐ENV:Envelope xmlns:SOAP-‐ENV="http://schemas.xmlsoap.org/soap/envelope/"> <SOAP-‐ENV:Body> <ns1:getProduct xmlns:ns1="http://agavi.org/sampleapp"> <id>987654</id> </ns1:getProduct> </SOAP-‐ENV:Body></SOAP-‐ENV:Envelope>
HTTP/1.1 500 Internal Service ErrorContent-‐Type: text/xml; charset=utf-‐8
<?xml version="1.0" encoding="UTF-‐8"?><SOAP-‐ENV:Envelope xmlns:SOAP-‐ENV="http://schemas.xmlsoap.org/soap/envelope/"> <SOAP-‐ENV:Body> <SOAP-‐ENV:Fault> <faultcode>SOAP-‐ENV:Server</faultcode> <faultstring>Unknown Product </faultstring> </SOAP-‐ENV:Fault> </SOAP-‐ENV:Body></SOAP-‐ENV:Envelope>
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SOAP sucks, said everyone
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let's build APIs without the clutter, they said
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POST /api/talk HTTP/1.1Host: joind.inContent-‐Type: text/xml; charset=utf-‐8
<?xml version="1.0" encoding="UTF-‐8"?><request> <auth> <user>Chuck Norris</user> <pass>roundhousekick</pass> </auth> <action type="getdetail"> <talk_id>42</talk_id> </action></request>
HTTP/1.1 200 OKContent-‐Type: text/xml; charset=utf-‐8
<?xml version="1.0" encoding="UTF-‐8"?><response> <item> <talk_title>My Test Talk</talk_title> <talk_desc>This is a sample talk description</talk_desc> <ID>42</ID> </item></response>
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PROBLEMS WITH THIS API
• Always a POST
•Doesn't use HTTP Authentication
•Operation information is enclosed in the request ("getdetail")
•Nothing there is cacheable
• Everything through one endpoint (/api/talks for talks)
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Level 0 in the Richardson Maturity Model:Plain old XML over the wire in an RPC fashion
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Room for improvement: use one URI for each resource.
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That would be Level 1 in Richardson's Maturity Model
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Level 0 and Level 1 are a bag of hurt.Do not use them.
Ever.
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ALONG CAME ROY FIELDINGAnd Gave Us REST
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that was awesome
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because everyone could say
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I haz REST nao
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when in fact
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they bloody didn’t
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RESTWhat Does That Even Mean?
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REpresentational State Transfer
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Roy Thomas Fielding: Architectural styles andthe design of network based software architectures.
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• Client-Server
• Stateless
• Cacheable
• Layered System
• Code on Demand (optional)
• Uniform Interface
REST CONSTRAINTS
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Simple explaination of the Uniform Interface
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• A URL identifies a Resource
•Methods perform operations on resources
• The operation is implicit and not part of the URL
• A hypermedia format is used to represent the data
• Link relations are used to navigate a service
UNIFORM INTERFACE
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a web page is not a resource
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it is a (complete) representation of a resource
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GET /products/ HTTP/1.1Host: acme.comAccept: application/json
HTTP/1.1 200 OKContent-‐Type: application/json; charset=utf-‐8Allow: GET, POST
[ { id: 1234, name: "Red Stapler", price: 3.14, location: "http://acme.com/products/1234" }]
GETTING JSON BACK
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GET /products/ HTTP/1.1Host: acme.comAccept: application/xml
HTTP/1.1 200 OKContent-‐Type: application/xml; charset=utf-‐8Allow: GET, POST
<?xml version="1.0" encoding="utf-‐8"?><products xmlns="urn:com.acme.products" xmlns:xl="http://www.w3.org/1999/xlink"> <product id="1234" xl:type="simple" xl:href="http://acme.com/products/1234"> <name>Red Stapler</name> <price currency="EUR">3.14</price> </product></products>
GETTING XML BACK
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no hypermedia formats yet in those examples!
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I will show that in a few minutes
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GET /products/ HTTP/1.1Host: acme.comAccept: application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,*/*;q=0.5User-‐Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_8; en-‐us) AppleWebKit…
HTTP/1.1 200 OKContent-‐Type: text/html; charset=utf-‐8Allow: GET, POST
<html lang="en"> <head> <meta http-‐equiv="Content-‐Type" content="text/html; charset=UTF-‐8"></meta> <title>ACME Inc. Products</title> </head> <body> <h1>Our Incredible Products</h1> <ul id="products"> <li><a href="http://acme.com/products/1234">Red Stapler</a> (€3.14)</li> </ul> </body></html>
AND FINALLY, HTML
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VOLUME ONEDesigning an HTTP Interface
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FIRST: DEFINE RESOURCESA Good Approach: Structure Your URLs
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BAD URLS
• http://www.acme.com/product/
• http://www.acme.com/product/filter/cats/desc
• http://www.acme.com/product/1234
• http://www.acme.com/photos/product/1234
• http://www.acme.com/photos/product/1234/new
• http://www.acme.com/photos/product/1234/5678
WTF?
sausage ID?
new what?
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GOOD URLS
• http://www.acme.com/products/
• http://www.acme.com/products/?filter=cats&sort=desc
• http://www.acme.com/products/1234
• http://www.acme.com/products/1234/photos/
• http://www.acme.com/products/1234/photos/?sort=latest
• http://www.acme.com/products/1234/photos/5678
a list of productsfiltering is a query
a single productall photos
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now here's the ironic part
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URLs don't matter once you have a fully RESTful interface
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but it’s helpful to think in terms of resources
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SECOND: USE RESOURCESCRUD, but not really
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COLLECTION OPERATIONS
• http://www.acme.com/products/
• GET to retrieve a list of products
• POST to create a new product
• returns
• 201 Created
• Location: http://www.acme.com/products/1235
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ITEM OPERATIONS
• http://www.acme.com/products/1234
• GET to retrieve
• PUT to update
•DELETE to, you guessed it, delete
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and remember
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don't let the server maintain client state (e.g. cookies)
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Now we are at Level 2 in RMM
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RMM LEVEL 2
• Use HTTP verbs
• GET (safe and idempotent)
• POST (unsafe, not idempotent)
• PUT & DELETE (unsafe, idempotent)
• Use HTTP status codes to indicate result success
• e.g. HTTP/1.1 409 Conflict
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THE TWITTER APINot RESTful, And Not Even Getting HTTP Right :(
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mind you we're not even inspecting the RESTfulness
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we're just looking at Twitter's API from an HTTP perspective
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• GET http://api.twitter.com/1/statuses/show/12345.json
• Problems:
•Operation (“show”) included in the URL
• Status ID not a child of the “statuses” collection
• Better : GET http://twitter.com/statuses/12345 with Accept header
STATUSES/SHOW
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• POST http://api.twitter.com/1/statuses/update.json
• Problems:
•Operation (“update”) included in the URL
• Uses the authenticated user implicitly
• Better : POST http://twitter.com/users/CaseySoftware/statuses/
STATUSES/UPDATE
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• POST http://api.twitter.com/1/statuses/destroy/12345.json
• Problems:
•Operation (“destroy”) included in the URL like it’s 1997
•Odd, illogical hierarchy again
• Allows both “POST” and “DELETE” as verbs
• Better : DELETE http://twitter.com/statuses/12345
STATUSES/DESTROY
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• GET http://api.twitter.com/1/statuses/retweets/12345.json
• Problems:
• Hierarchy is wrong
• Better : GET http://twitter.com/statuses/12345/retweets/
STATUSES/RETWEETS
![Page 78: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/78.jpg)
• PUT http://api.twitter.com/1/statuses/retweet/12345.format
• Problems:
• “retweets” collection exists, but is not used here
• As usual, the action is in the URL (“make retweet” is RPC-y)
• Allows both “PUT” and “POST” as verbs
• Better : POST http://twitter.com/statuses/12345/retweets/
STATUSES/RETWEET
![Page 79: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/79.jpg)
SUMMARY
• http://twitter.com/statuses/
• POST to create a new tweet
• http://twitter.com/statuses/12345
•DELETE deletes (PUT could be used for updates)
• http://twitter.com/statuses/12345/retweets/
• POST creates a new retweet
![Page 80: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/80.jpg)
ANGRY GERMAN SUMMARY
• Twitter's "REST" API sucks, hates HTTP and kills baby kittens.
![Page 81: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/81.jpg)
INTERMISSIONWhat's the Biggest Reason for the Success of the Web?
![Page 82: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/82.jpg)
WWW
![Page 83: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/83.jpg)
first data exchange system
![Page 84: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/84.jpg)
planetary scale
![Page 85: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/85.jpg)
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![Page 87: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/87.jpg)
why is that possible?
![Page 88: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/88.jpg)
Hyperlinks!
![Page 89: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/89.jpg)
no tight coupling!
![Page 90: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/90.jpg)
loosely coupled by design
![Page 91: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/91.jpg)
no notification infrastructure
![Page 92: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/92.jpg)
HTTP/1.1 404 Not Found
![Page 93: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/93.jpg)
embraces failure
![Page 94: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/94.jpg)
more information != more friction
![Page 95: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/95.jpg)
no limits to scalability
![Page 96: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/96.jpg)
WWW is protocol-centric
![Page 97: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/97.jpg)
VOLUME TWORESTful Services with Hypermedia
![Page 98: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/98.jpg)
THE UNIFORM INTERFACE
• Identification of Resources (e.g. through URIs)
• Representations are conceptually separate!
•Manipulation Through Representations (i.e. they are complete)
• Self-Descriptive Messages (containing all information)
• Hypermedia As The Engine Of Application State ("HATEOAS")
magic awesomesauce essential to REST
![Page 99: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/99.jpg)
HATEOASThe Missing Piece in the Puzzle
![Page 100: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/100.jpg)
ONE LAST PIECE IS MISSING
• How does a client know what to do with representations?
• How do you go to the “next” operation?
•What are the URLs for creating subordinate resources?
•Where is the contract for the service?
![Page 101: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/101.jpg)
HYPERMEDIA AS THE ENGINE OF APPLICATION STATE
• Use links to allow clients to discover locations and operations
• Link relations are used to express the possible options
• Clients do not need to know URLs, so they can change
• The entire application workflow is abstracted, thus changeable
• The hypermedia type itself could be versioned if necessary
•No breaking of clients if the implementation is updated!
![Page 102: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/102.jpg)
(X)HTML and Atom are Hypermedia formats
![Page 103: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/103.jpg)
Or you roll your own...
![Page 104: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/104.jpg)
GET /products/1234 HTTP/1.1Host: acme.comAccept: application/vnd.com.acme.shop+xml
HTTP/1.1 200 OKContent-‐Type: application/vnd.come.acme.shop+xml; charset=utf-‐8Allow: GET, PUT, DELETE
<?xml version="1.0" encoding="utf-‐8"?><product xmlns="urn:com.acme.prods" xmlns:atom="http://www.w3.org/2005/Atom"> <id>1234</id> <name>Red Stapler</name> <price currency="EUR">3.14</price> <atom:link rel="payment" type="application/vnd.com.acme.shop+xml" href="http://acme.com/products/1234/payment"/></product>
re-use Atom forlink relations
meaning defined in IANA Link Relations list
A CUSTOM MEDIA TYPE
Remind clients ofUniform Interface :)
![Page 105: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/105.jpg)
boom, RMM Level 3
![Page 106: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/106.jpg)
XML is really good for hypermedia formats
![Page 107: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/107.jpg)
(hyperlinks, namespaced attributes, re-use of formats, …)
![Page 108: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/108.jpg)
JSON is more difficult
![Page 109: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/109.jpg)
(no hyperlinks, no namespaces, no element attributes)
![Page 110: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/110.jpg)
<?xml version="1.0" encoding="utf-‐8"?><product xmlns="urn:com.acme.prods" xmlns:atom="http://www.w3.org/2005/xlink"> <id>1234</id> <name>Red Stapler</name> <price currency="EUR">3.14</price> <atom:link rel="payment" type="application/com.acme.shop+xml" href="http://acme.com/products/1234/payment"/></product>
{ id: 1234, name: "Red Stapler", price: { amount: 3.14, currency: "EUR" }, links: [ { rel: "payment", type: "application/vnd.com.acme.shop+json", href: "http://acme.com/products/1234/payment" } ]}
XML VERSUS JSON
![Page 111: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/111.jpg)
also, JSON is hard to evolve without breaking clients
![Page 112: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/112.jpg)
<?xml version="1.0" encoding="utf-‐8"?><products xmlns="http://acme.com/shop/products"> <product id="123"> <name>Bacon</name> <price>5.99</price> </product></products>
![Page 113: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/113.jpg)
<?xml version="1.0" encoding="utf-‐8"?><products xmlns="http://acme.com/shop/products"> <product id="123"> <name>Bacon</name> <price>5.99</price> OMNOMNOM Bacon </product></products>
![Page 114: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/114.jpg)
<?xml version="1.0" encoding="utf-‐8"?><products xmlns="http://acme.com/shop/products"> <product id="123"> <name>Bacon</name> <price>5.99</price> <price currency="EUR">4.49</price> </product></products>
![Page 115: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/115.jpg)
<?xml version="1.0" encoding="utf-‐8"?><products xmlns="http://acme.com/shop/products"> <product id="123"> <name xml:lang="en">Bacon</name> <name xml:lang="de">Speck</name> <price>5.99</price> </product></products>
![Page 116: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/116.jpg)
<?xml version="1.0" encoding="utf-‐8"?><products xmlns="http://acme.com/shop/products"> <product id="123"> <name xml:lang="en">Bacon</name> <name xml:lang="de">Speck</name> <price>5.99</price> <link rel="category" href="..." /> </product></products>
![Page 117: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/117.jpg)
and hey
![Page 118: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/118.jpg)
without hypermedia, your HTTP interface is not RESTful
![Page 119: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/119.jpg)
that’s totally fineand sometimes even the only way to do it
![Page 120: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/120.jpg)
(e.g. CouchDB or S3 are never going to be RESTful)
![Page 121: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/121.jpg)
just avoid calling it a "REST API" :)
![Page 122: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/122.jpg)
good hypermedia format example: the Lovefilm API
![Page 123: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/123.jpg)
<?xml version="1.0" encoding="utf-‐8" standalone="yes"?><search> <total_results>6</total_results> <items_per_page>1</items_per_page> <start_index>1</start_index> <link href="http://openapi.lovefilm.com/catalog/games?start_index=1&items_per_page=1&term=old" rel="self" title="self"/> <link href="http://openapi.lovefilm.com/catalog/games?start_index=2&items_per_page=1&term=old" rel="next" title="next"/> <link href="http://openapi.lovefilm.com/catalog/games?start_index=6&items_per_page=1&term=old" rel="last" title="last"/> <catalog_title> <can_rent>true</can_rent> <release_date>2003-‐09-‐12</release_date> <title full="Star Wars: Knights of the Old Republic" clean="Star Wars: Knights of the Old Republic"/> <id>http://openapi.lovefilm.com/catalog/title/59643</id> <adult>false</adult> <number_of_ratings>574</number_of_ratings> <rating>4</rating> <category scheme="http://openapi.lovefilm.com/categories/catalog" term="games"/> <category scheme="http://openapi.lovefilm.com/categories/format" term="Xbox"/> <category scheme="http://openapi.lovefilm.com/categories/genres" term="Adventure"/> <category scheme="http://openapi.lovefilm.com/categories/genres" term="Role-‐playing"/> <category scheme="http://openapi.lovefilm.com/categories/certificates/bbfc" term="TBC"/> <link href="http://openapi.lovefilm.com/catalog/title/59643/synopsis" rel="http://schemas.lovefilm.com/synopsis" title="synopsis"/> <link href="http://openapi.lovefilm.com/catalog/title/59643/reviews" rel="http://schemas.lovefilm.com/reviews" title="reviews"/> <link href="http://www.lovefilm.com/product/59643-‐Star-‐Wars-‐Knights-‐of-‐the-‐Old-‐Republic.html?cid=LFAPI" rel="alternate" title="web page"/> </catalog_title></search>
![Page 124: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/124.jpg)
ROOM FOR IMPROVEMENT IN THE LOVEFILM API
• Uses application/xml instead of a custom media type
•Once that is fixed, all the link elements could also have a “type” attribute indicating the media type
• Should use XML namespaces on the root element, with one namespace per type (e.g. “urn:com.lovefilm.api.item”, “urn:com.lovefilm.api.searchresult” and so on)
• That way, clients can determine the resource type easily
![Page 125: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/125.jpg)
another great RESTful API: Huddle
![Page 126: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/126.jpg)
<document xmlns="http://schema.huddle.net/2011/02/" title="TPS report May 2010" description="relentlessly mundane and enervating."> <link rel="self" href="..." /> <link rel="parent" href="..." title="..."/> <link rel="edit" href="..." /> <link rel="delete" href="..." /> <link rel="content" href="..." title="..." type="..." /> <link rel="thumb" href="..." /> <link rel="version-‐history" href="..." /> <link rel="create-‐version" href="..." /> <link rel="comments" href="..." /> <actor name="Peter Gibson" rel="owner"> <link rel="self" href="..." /> <link rel="avatar" href="..." type="image/jpg" /> <link rel="alternate" href="..." type="text/html" /> </actor> <actor name="Barry Potter" rel="updated-‐by"> <link rel="self" href="..." /> <link rel="avatar" href="..." type="image/jpg" /> <link rel="alternate" href="..." type="text/html" /> </actor> <size>19475</size> <version>98</version> <created>2007-‐10-‐10T09:02:17Z</created> <updated>2011-‐10-‐10T09:02:17Z</updated> <processingStatus>Complete</processingStatus> <views>9</views></document>
![Page 127: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/127.jpg)
ROOM FOR IMPROVEMENT IN THE HUDDLE API
• Uses custom rels like “thumb” or “avatar” not defined in the IANA registry (http://www.iana.org/assignments/link-relations)
• Risk of collisions and ambiguity; should use something like “http://rels.huddle.net/thumb” instead.
• Uses one global XML schema and namespace for all entities
• Clients cannot detect entity type based on namespace
•Difficult to evolve schema versions independently
![Page 128: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/128.jpg)
API VERSIONINGMedia Types To The Rescue!
![Page 129: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/129.jpg)
why not api.myservice.com/v1/foo/bar?and then api.myservice.com/v2/foo/bar?
![Page 130: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/130.jpg)
different URLs means different resources!
![Page 131: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/131.jpg)
also, keep bookmarks (by machines) in mind
![Page 132: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/132.jpg)
GET /products HTTP/1.1Host: acme.comAccept: application/vnd.com.myservice+xml
HTTP/1.1 200 OKContent-‐Type: application/vnd.com.myservice+xml; charset=utf-‐8Allow: GET, POST
<?xml version="1.0" encoding="utf-‐8"?><products xmlns="urn:com.acme.products" xmlns:xl="http://www.w3.org/1999/xlink"> <product id="1234" xl:type="simple" xl:href="http://acme.com/products/1234"> <name>Red Stapler</name> <price currency="EUR">3.14</price> </product></products>
API VERSION 1
![Page 133: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/133.jpg)
(some years pass...)
![Page 134: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/134.jpg)
GET /products HTTP/1.1Host: acme.comAccept: application/vnd.com.myservice.v2+xml
HTTP/1.1 200 OKContent-‐Type: application/vnd.com.myservice.v2+xml; charset=utf-‐8Allow: GET, POST
<?xml version="1.0" encoding="utf-‐8"?><products xmlns="urn:com.acme.products" xmlns:xl="http://www.w3.org/1999/xlink"> <product id="1234" xl:type="simple" xl:href="http://acme.com/products/1234"> <name>Red Stapler</name> <price currency="EUR">3.14</price> <availability>false</availability> </product></products>
API VERSION 2
![Page 135: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/135.jpg)
clients can’t upgrade protocol for known URLs!
![Page 136: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/136.jpg)
Also, imagine every install of phpBB or TYPO3 had an API
![Page 137: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/137.jpg)
If the version is in the URL, clients need to regex those
![Page 138: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/138.jpg)
http://sharksforum.org/community/api/v1/threads/102152
![Page 139: Designing HTTP Interfaces and RESTful Web Services (PHPDAY2012 2012-05-20)](https://reader031.fdocuments.us/reader031/viewer/2022013011/54b7a76e4a7959b0218b45c8/html5/thumbnails/139.jpg)
http://forum.sharksforum.org/api/v1/threads/102152
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that would be fail
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or what if another forum software wants the same API?
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also would have to use “/v1/” in their URLs
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URI based versioning kills interoperability
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YOU MIGHT BE WONDERINGWhy Exactly Is This Awesome?
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THE MERITS OF REST
• Easy to evolve: add new features or elements without breaking BC
• Easy to learn: developers can "browse" service via link rels
• Easy to scale up: grows well with number of features, users and servers
• Easy to implement: build it on top of HTTP, and profit!
• Authentication & TLS
• Caching & Load Balancing
• Conditional Requests
• Content Negotiation
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but...
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hold on, you say
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a plain HTTP-loving service does the job, you say
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surely, there is a merit to REST beyond extensibility, you ask
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nope
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"REST is software design on the scale of decades: every detail is intended to promote software longevity and independent evolution. Many of the constraints are directly opposed to short-term efficiency. Unfortunately, people are fairly good at short-term design, and usually awful at long-term design."
Roy Fielding
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"Most of REST's constraints are focused on preserving independent evolvability over time, which is only measurable on the scale of years. Most developers simply don't care what happens to their product years after it is deployed, or at least they expect to be around to rewrite it when such change occurs."
Roy Fielding
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FURTHER READING
• Ryan TomaykoHow I Explained REST to my Wifehttp://tomayko.com/writings/rest-to-my-wife
• Jim Webber, Savas Parastatidis & Ian RobinsonHow to GET a Cup of Coffeehttp://www.infoq.com/articles/webber-rest-workflow
• Roy Thomas FieldingArchitectural Styles and the Design of Network-based Software Architectureshttp://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm
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BOOKS ON REST
• Jim Webber, Savas Parastatidis, Ian RobinsonREST in PracticeISBN: 978-0596805821
• Subbu AllamarajuRESTful Web Services CookbookISBN: 978-0596801687
• Leonard Richardson, Sam RubyRESTful Web ServicesISBN: 978-0596529260
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!e End
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Questions?