1. AJAX and REST

2. 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

3. What is AJAX? It uses the HTTPRequest and HTTPResponse objects to
Make a server request from client JavaScript
And process the server-side response

4. AJAX (model)
From W3Schools.com

5. 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

6. RestFull APIs
These are generally available API that accept and execute AJAX requests
Yahoo has YQL
SQL-like queries are built into the URL (GET request)
I’ll show this in class

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

8. 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

9. AJAX XMLHttpRequest The following creates the request
var req = new XMLHttpRequest();
The open method define the type of request
The first argument contains the method to use (GET or POST)
The second argument contains the URL
The third argument contains true (asynchronous) or false (synchronous)
The send method sends the request to the server

10. AJAX XMLHttpRequest (Example)
Create open and send a synchronous request

11. 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

12. AJAX Response (Synchronous)

13. 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

14. AJAX Response (Asynchronous)

15. AJAX (jQuery)
As usual, jQuery makes the process simple

16. 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

17. A Few Words about XML
Sample XML document

18. REST Acronym for Representational State Transfer
REST (restful Web services) is a way of exchanging HTTP requests and responses between client and server
It’s an alternative to Web Services and SOAP
It’s an alternative to Remote Procedure Calls (RPC)

19. 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

20. A Few Words about YQL Yahoo Query Language
Implemented as a Web service, they maintain a number of tables
Finance
Geography and many more

21. AJAX (References) http://w3schools.com/ajax/default.asp

22. HTML 5