Designing an API

The glorious REST  Representional State Transfer  Highly Scalable  Uses URI identifiers  No state on server side  Hyperlinked  No uniform standard  NOT A PROTOCOL Copyright © 2013 Twobo Technologies AB. All rights reserved

Resource or service Copyright © 2013 Twobo Technologies AB. All rights reserved http://martinfowler.com/articles/richardsonMaturityModel.html Level 0: The Swamp of POX Level 1: Resource Level 2: HTTP Verbs Level 3: Hypermedia Controls Glory of Rest

Level 0 Swamp of POX Copyright © 2013 Twobo Technologies AB. All rights reserved Copyright © 2013 Twobo Technologies AB. All rights reserved POST <getBook> POST <deleteUser> <book ... <ok ... /api  XML RPC all over again

Level 2 HTTP Verbs  Utilizes the semantics of HTTP Copyright © 2013 Twobo Technologies AB. All rights reserved GET - Read a resource HEAD – Read metadata about resource OPTIONS – Read what operations are available POST – Add a new resource, or run operation PUT – Replace existing resource completely DELETE – Remove resource (PATCH – Update existing resource in place) GET ?pagesize=A4 DELETE 200 OK <book ... 201 No Content /books/2 /users/32

Level 3 The Glory of REST  HATEOAS  Hypermedia As The Engine Of Application State  Or simply: Hypermedia  Let the Media Type tell you what to do  Hyperlink, hyperlink hyperlink Copyright © 2013 Twobo Technologies AB. All rights reserved

Example Copyright © 2013 Twobo Technologies AB. All rights reserved curl –v http://localhost/stuff <stuff xmlns:tt=http://example.com/rest tt:rel=”/stuff"> <more-stuff tt:rel="/stuff/more-stuff"/> <other-stuff tt:=”/stuff/other-stuff"/> <data> <entry>Interesting 1</entry> <entry>Interesting 2</entry> </stuff> curl –v http://localhost/stuff/more-stuff <more-stuff xmlns:tt=http://example.com/rest tt:rel=”/stuff/more-stuff"> <things tt:rel="/stuff/more-stuff/things"/> </more-stuff>

Ring a bell? Copyright © 2013 Twobo Technologies AB. All rights reserved curl –v http://localhost/v2/stuff <html> <div id=“stuff”> <a href=“/stuff/more-stuff”/> <a href=“/stuff/other-stuff/> <ol id=“data”> <li id=“entry1”>Interesting 1</li> <li id=“entry2”>Interesting 2</li> </ol> <form action=“/stuff” > <input type=“text” name=“value” /> </form> </div> </html>

The power of Mashups  Web mashup is easy  API mashup is harder  But the payoff is greater  API aggregation is really hard  And believe me, you’ll need to do it anyway… Copyright © 2013 Twobo Technologies AB. All rights reserved

Why is it hard  Different backend states and protocols  Different authentication methods  Different lookup schemes  Backend versioning Copyright © 2013 Twobo Technologies AB. All rights reserved 1st Original API New ‘Aggregated’ API 2ndOriginal API Operationally interesting

Aggregators  Don’t invent the wheel  Once your API is advanced enough, you’ll have to mash-up  But do you need aggregation?  If so: Identify the “operationally interesting” area  Focus on that  Mashup the rest Copyright © 2013 Twobo Technologies AB. All rights reserved

Designing an API

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