AJAX and REST - Web Programming - Lecture Slides, Slides of Computer Programming

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AJAX and REST

What is AJAX?

 It’s an acronym for Asynchronous JavaScript and XML  Although requests need not be asynchronous  It’s not really a single technology but several  HTML / CSS / DOM / XML  It’s used to dynamically update Web pages  or at least parts of them

AJAX (model)

From W3Schools.com

AJAX Frameworks

 Most vendors have their own AJAX abstraction layers  ASP has a script manager and an AJAX toolkit  It’s a layer on top of AJAX  There are several for PHP  Phery, CJAX, Quicknet  There are frameworks for Python, Perl, Ruby and others

RestFull APIS

 Google has a number of APIs  These use JSON typically  JSON is an alternative to moving the responses around as XML

AJAX (The Mechanics)

 The XMLHttpRequest object is used to create a request  The request gets configured with the open method  The request gets sent with the send method  The responseText and responseXML properties store the returned information  Use the onreadystatechange event for async requests

AJAX XMLHttpRequest

(Example)

 Create open and send a synchronous request

AJAX Response (Synchronous)

 When the request completes, we get at the response through the following properties of the XMLHttpRequest object  responseText – gets the response data as a string  responseXML gets the response data as XML, which we can then parse using the DOM  This is the same DOM we talked about

AJAX Response

(Asynchronous)

 The onreadystatechanged event fires as the request progresses  Initialize  Loading  Loaded  Interactive  Completed  Status and status contain the result status information  404 – not found / 200 success docsity.com

AJAX Response

(Asynchronous)

A Few Words about XML

 It’s the extensible markup language  Data is frequently stored and transported as XML  It looks like XHTML 5  Tags, attributes and elements  Nesting concepts are the same  However the tag and attribute names can be any valid name  .NET knows about them

A Few Words about XML

 Sample XML document

REST

 For read requests we  Send all data to the server via a URL and GET request  URLs are a logical location, rather than a physical resource  Data is typically returned as XML  It’s not a standard but a way of doing things  An architecture of style  YQL is restful

A Few Words about YQL

 Yahoo Query Language  Implemented as a Web service, they maintain a number of tables  Finance  Geography and many more

http://developer.yahoo.com/yql/guide/yql- opentables-chapter.html#