REST and AJAX Reconciled

Slideshow Transcript

1. Slide 1: REST and AJAX reconciled Lars Trieloff at AJAX World East 2008
2. Slide 2: What is REST?
3. Slide 3: What is REST? • Buzzword
4. Slide 4: What is REST? • Buzzword • Alternative to SOAP
5. Slide 5: What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer
6. Slide 6: What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer • Architecture of the World Wide Web
7. Slide 7: What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer • Architecture of the World Wide Web • Architecture for Scalable Network Applications
8. Slide 8: How do we start? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
9. Slide 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. Slide 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. Slide 11: Resources have Representations Representation Resource Representation URI Representations can have different formats (HTML, XML, JSON) or show different aspects of a resource.
12. Slide 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. Slide 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. Slide 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. Slide 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. Slide 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. Slide 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. Slide 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. Slide 19: How do we go on? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
20. Slide 20: What are REST Clients • Libwww • Microsoft Internet Explorer • Apache Commons HTTPClient • Mozilla Firefox • Python httplib • Apple Safari • Ruby Net::HTTP • Opera
21. Slide 21: HTTP Client Libraries + Full HTTP Support + Desktop Applications +Server-side mashups - Not in the web browser
22. Slide 22: Web Browsers as HTTP Clients + No client needed +Everywhere installed - Weak HTTP Support - Web Forms 1.0 - Browser Bugs
23. Slide 23: Web Forms 1.0 <form action=\"/blog\" method=\"POST\" > enctype=\"application/x-www-form-urlencoded\" label> <label for=\"title\">Title</ > <input type=\"text\" name=\"title\" <label for=\"text\">Entry</label> <textarea name=\"text\"> </textarea> <input type=\"submit\"> </form>
24. Slide 24: Web Forms 1.0 w do I e But ho chang <foally icrmction=g/bt og\" dynam ioan (tar\" e l the act me) hofdthPe ST\"ication/x-www-form-urlencoded\"> t =\" O rcee coype=\"appl resou n t? foabm for=\"title\">Title</label> <l r el > <input type=\"text\" name=\"title\" <label for=\"text\">Entry</label> <textarea name=\"text\"> </textarea> <input type=\"submit\"> </form>
25. Slide 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 og\" dynam ioan (tar\" e l and P ethods DELET the act me) hofdthPe ST\"ication/x-www-formEuarencoUeda>nd t =\" O oype=\"appl T\" sourcee ct ignore - rle d re n d? fo rm? \"title\">Title</label> <label for= > <input type=\"text\" name=\"title\" <label for=\"text\">Entry</label> <textarea name=\"text\"> </textarea> <input type=\"submit\"> </form>
26. Slide 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 og\" dynam ioan (tar\" e l and P ethods DELET the act me) hofdthPe ST\"ication/x-www-formEuarencoUeda>nd t =\" O oype=\"appl T\" sourcee ct ignore - rle d re n d? fo rm? \"title\">Title</label> <label for= > type=\"text\" name=\"title\" <input <label How do I specify a for=\"text\">Entry</label> different <textarea name=\"text\"> </textarea> encoding, for <input type=\"submit\"> </form> example XML or JSON?
27. Slide 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. Slide 28: Solution for now: making browsers better HTTP clients using AJAX
29. Slide 29: Where are we now? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
30. Slide 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. Slide 31: Getting alternate Representations <head> tle> <title>REST and AJAX</ti =\"text/json\"> <link rel=\"alterna te\" href=\"this.json\" type cript\"> <script type=\"text/javas function initRest() { TagName(\"link\"); var links = document.getElementsBy ntries\"); var entries = do cument.getElementById(\"e for (link in links) { nate\") { if (links[link].rel==\"alter list of entries //pull data and populate entries with a } } } </script> </head> \"> <body onload=\"initRest() <ul id=\"entries\"> </ul> </body>
32. Slide 32: Overloading Forms \" <form a ction=\"/blog method=\"PUT\" enctype= \"text/json\" urn false;\"> orm(this);ret ons ubmit=\"RESTF Title</title> <label for=\"title\"> it le</label> <label f or=\"title\">T n ame=\"title\"> <input type=\"text\" > > Entry</label <labe l for=\"text\" <textarea name=\"text\"> </textarea> <input typ e=\"submit\"> </form>
33. Slide 33: Data-only requests function RESTForm(fo rm) { var json = \"{\" + \"title: \" + form.tit le.value +\", \" + \"text: \" + form.text .value + \"}\"; var xmlhttp = (windo w.XMLHttpRequest) ? new XMLHttpRequest() : ActiveXObject(\"Micro soft.XMLHTTP\"); xmlhttp.open(form.me thod, form.action); xmlhttp.send(json); }
34. Slide 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. Slide 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. Slide 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. Slide 37: What is next? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
38. Slide 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. Slide 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. Slide 40: How do we go on? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
41. Slide 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. Slide 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. Slide 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. Slide 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. Slide 45: Never leave without screenshots resource or http://l iented urls integration dojo widget ocalhost :7402/my data/ent ries.lis t.html
46. Slide 46: Never leave without screenshots dojo widget integration
47. Slide 47: What we heard today • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX
48. Slide 48: Thank you very much lars.trieloff@day.com For more information, see my weblog at http://weblogs.goshaky.com/weblog/lars