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REST and AJAX Reconciled

  1. REST and AJAX reconciled Lars Trieloff at AJAX World East 2008
  2. What is REST?
  3. What is REST? • Buzzword
  4. What is REST? • Buzzword • Alternative to SOAP
  5. What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer
  6. What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer • Architecture of the World Wide Web
  7. What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer • Architecture of the World Wide Web • Architecture for Scalable Network Applications
  8. How do we start? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
  9. Things are Resources Resource Resources can be items of information (a blog entry) or or informational descriptions of real things (a blog author)
  10. Resources have URIs Resource URI Uniform Resource Identifier are unique ids for resources, just like ISBN for a book or a driver’s license for a person
  11. Resources have Representations Representation Resource Representation URI Representations can have different formats (HTML, XML, JSON) or show different aspects of a resource.
  12. Representations have URLs URL URL Representation Resource Representation URI Uniform Resource Locators describe how to get to a representation of a resource, they include protocol, hostname, path and extra information
  13. Clients interact via Verbs GET URL POST PUT URL DELETE Representation Resource Representation URI Uniform Resource Locators describe how to get to a representation of a resource, they include protocol, hostname, path and extra information
  14. GET is for reading GET Representation Representation Resource Resource Before After GET is a “safe” method. There are no side-effects, and the requested resource stays unmodified.
  15. PUT is for replacing PUT Representation Representation Resource Resource Before After PUT is a “idempotent” method. Issuing the same PUT request multiple times yields the same result.
  16. DELETE is for deleting DELETE Representation Resource Before After DELETE is also “idempotent”. Deleting a resource twice yields the same result - the resource is gone.
  17. POST is for action POST Representation Representation Representation Resource Resource Resource Before After POST is neither safe nor idempotent. It is used for updating, creating and executing resources.
  18. So what? • There are unlimited resources • Every resource can be addressed • There are only four verbs • Resources have an uniform interface This makes it easy to write clients for existing REST applications and makes it easy to expose a RESTful interface to an application.
  19. How do we go on? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
  20. What are REST Clients • Libwww • Microsoft Internet Explorer • Apache Commons HTTPClient • Mozilla Firefox • Python httplib • Apple Safari • Ruby Net::HTTP • Opera
  21. HTTP Client Libraries + Full HTTP Support + Desktop Applications +Server-side mashups - Not in the web browser
  22. Web Browsers as HTTP Clients + No client needed +Everywhere installed - Weak HTTP Support - Web Forms 1.0 - Browser Bugs
  23. Web Forms 1.0 <form action=quot;/blogquot; method=quot;POSTquot; > enctype=quot;application/x-www-form-urlencodedquot; label> <label for=quot;titlequot;>Title</ > <input type=quot;textquot; name=quot;titlequot; <label for=quot;textquot;>Entry</label> <textarea name=quot;textquot;> </textarea> <input type=quot;submitquot;> </form>
  24. Web Forms 1.0 w do I e But ho chang <foally icrmction=g/bt ogquot; dynam ioan (tarquot; e l the act me) hofdthPe STquot;ication/x-www-form-urlencodedquot;> t =quot; O rcee coype=quot;appl resou n t? foabm for=quot;titlequot;>Title</label> <l r el > <input type=quot;textquot; name=quot;titlequot; <label for=quot;textquot;>Entry</label> <textarea name=quot;textquot;> </textarea> <input type=quot;submitquot;> </form>
  25. Web Forms 1.0 Why w do I e But ho chang and P do only <foally work OST m GET icrmction=g/bt ogquot; dynam ioan (tarquot; e l and P ethods DELET the act me) hofdthPe STquot;ication/x-www-formEuarencoUeda>nd t =quot; O oype=quot;appl Tquot; sourcee ct ignore - rle d re n d? fo rm? quot;titlequot;>Title</label> <label for= > <input type=quot;textquot; name=quot;titlequot; <label for=quot;textquot;>Entry</label> <textarea name=quot;textquot;> </textarea> <input type=quot;submitquot;> </form>
  26. Web Forms 1.0 Why w do I e But ho chang and P do only <foally work OST m GET icrmction=g/bt ogquot; dynam ioan (tarquot; e l and P ethods DELET the act me) hofdthPe STquot;ication/x-www-formEuarencoUeda>nd t =quot; O oype=quot;appl Tquot; sourcee ct ignore - rle d re n d? fo rm? quot;titlequot;>Title</label> <label for= > type=quot;textquot; name=quot;titlequot; <input <label How do I specify a for=quot;textquot;>Entry</label> different <textarea name=quot;textquot;> </textarea> encoding, for <input type=quot;submitquot;> </form> example XML or JSON?
  27. Solutions: • Changing the action dynamically: URI Templates • Other Methods than POST and GET: Web Forms 2.0 • More advanced encodings: Web Forms 2.0 http://bitworking.org/projects/URI-Templates/ http://www.whatwg.org/specs/web-forms/current-work/
  28. Solution for now: making browsers better HTTP clients using AJAX
  29. Where are we now? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
  30. With AJAX we can • get data-only (JSON) representations of web pages in the background • Overload Web Forms 1.0 behavior, and make them 2.0 • issue data-only (JSON) HTTP requests to these very resources
  31. Getting alternate Representations <head> tle> <title>REST and AJAX</ti =quot;text/jsonquot;> <link rel=quot;alterna tequot; href=quot;this.jsonquot; type criptquot;> <script type=quot;text/javas function initRest() { TagName(quot;linkquot;); var links = document.getElementsBy ntriesquot;); var entries = do cument.getElementById(quot;e for (link in links) { natequot;) { if (links[link].rel==quot;alter list of entries //pull data and populate entries with a } } } </script> </head> quot;> <body onload=quot;initRest() <ul id=quot;entriesquot;> </ul> </body>
  32. Overloading Forms quot; <form a ction=quot;/blog method=quot;PUTquot; enctype= quot;text/jsonquot; urn false;quot;> orm(this);ret ons ubmit=quot;RESTF Title</title> <label for=quot;titlequot;> it le</label> <label f or=quot;titlequot;>T n ame=quot;titlequot;> <input type=quot;textquot; > > Entry</label <labe l for=quot;textquot; <textarea name=quot;textquot;> </textarea> <input typ e=quot;submitquot;> </form>
  33. Data-only requests function RESTForm(fo rm) { var json = quot;{quot; + quot;title: quot; + form.tit le.value +quot;, quot; + quot;text: quot; + form.text .value + quot;}quot;; var xmlhttp = (windo w.XMLHttpRequest) ? new XMLHttpRequest() : ActiveXObject(quot;Micro soft.XMLHTTPquot;); xmlhttp.open(form.me thod, form.action); xmlhttp.send(json); }
  34. Planning RESTful AJAX applications 1. Define the domain model 2. Define Resources, Resource Types and URIs 3. Define Representations for Resources 4. Define POST behavior
  35. Watch out! common pitfalls and how to cope with them • Problem: Some browsers do not support PUT or DELETE requests, even as XHR • Solution: Wrap your PUT or DELETE Request in a POST request and add the X- HTTP-Method-Override Header
  36. Watch out! common pitfalls and how to cope with them • Problem: Some browsers do not handle 301 or 302 response codes for redirects properly • Solution: Define a format for redirection messages that wraps headers such as Location and Status codes in JSON
  37. What is next? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
  38. Framework Checklist frameworks can help getting the job done • Resource-based approach? • having something like /action/view/1 is a warning sign • Acknowledges existence of Representations? • you need multiple representations • Solid engineering, community, support? • without, you can do it on your own
  39. Framework Examples frameworks that can help getting the job done • Apache Cocoon • based on XML pipelines, URL patterns, selectors • RESTlet • Like Servlets for REST. Good for existing models • Apache Sling • based on JCR, a database for resources, with server- side scripting support
  40. How do we go on? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
  41. Sling with µjax • Exposes the complete JCR repository (Resource Database) as JSON tree • API for reading, creating, writing, deleting and moving Resources • Stand-alone Javascript library, plays nicely with your framework • Extra: Dojo Toolkit Integration
  42. µjax Core Principles I browser & ujax.js reading: json & resource GET’s writing: form-POST & GET s s J2EE Web Server 3 2 Browser I 2 UjaxServlet.java translating requests to JCR calls 3 JCR Compliant Content Repository
  43. µjax Core Principles I browser & ujax.js reading: json & resource GET’s writing: form-POST & GET s s J2EE Web Server 3 2 Browser I very simple js A 2 UjaxServlet.java translating requests read content, FoPI to to JCR calls r to write contenms t 3 JCR Compliant Content Repository
  44. µjax Core Principles I browser & ujax.js reading: json & resource GET’s writing: form-POST & GET s s J2EE Web Server 3 2 handles all the h particularly se eavy lifting, curity Browser I 16 t ons very simple js A 2 UjaxServlet.java translating requests read content, FoPI to to JCR calls r to write contenms t 3 JCR Compliant Content Repository
  45. Never leave without screenshots resource or http://l iented urls integration dojo widget ocalhost :7402/my data/ent ries.lis t.html
  46. Never leave without screenshots dojo widget integration
  47. What we heard today • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
  48. Thank you very much lars.trieloff@day.com For more information, see my weblog at http://weblogs.goshaky.com/weblog/lars

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