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REST and AJAX Reconciled

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Information about REST and AJAX Reconciled

Published on March 19, 2008

Author: lars3loff

Source: slideshare.net

Description

Lars Trieloff's presentation on REST and AJAX held at AJAX World East 2008 in New York.
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REST and AJAX reconciled Lars Trieloff at AJAX World East 2008

What is REST?

What is REST? • Buzzword

What is REST? • Buzzword • Alternative to SOAP

What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer

What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer • Architecture of the World Wide Web

What is REST? • Buzzword • Alternative to SOAP • Representational State Transfer • Architecture of the World Wide Web • Architecture for Scalable Network Applications

How do we start? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX

Things are Resources Resource Resources can be items of information (a blog entry) or or informational descriptions of real things (a blog author)

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

Resources have Representations Representation Resource Representation URI Representations can have different formats (HTML, XML, JSON) or show different aspects of a resource.

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

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

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.

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.

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.

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.

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.

How do we go on? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX

What are REST Clients • Libwww • Microsoft Internet Explorer • Apache Commons HTTPClient • Mozilla Firefox • Python httplib • Apple Safari • Ruby Net::HTTP • Opera

HTTP Client Libraries + Full HTTP Support + Desktop Applications +Server-side mashups - Not in the web browser

Web Browsers as HTTP Clients + No client needed +Everywhere installed - Weak HTTP Support - Web Forms 1.0 - Browser Bugs

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>

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>

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>

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?

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/

Solution for now: making browsers better HTTP clients using AJAX

Where are we now? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX

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

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>

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>

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); }

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

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

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

What is next? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX

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

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

How do we go on? • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX

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

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

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

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

Never leave without screenshots resource or http://l iented urls integration dojo widget ocalhost :7402/my data/ent ries.lis t.html

Never leave without screenshots dojo widget integration

What we heard today • Introduction • Core Concepts • REST Clients • AJAX REST Clients • REST Frameworks • REST Frameworks for AJAX

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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