REST-style web services use HTTP method verbs to designate the
basic action and URL variables to specify the action details. For
example, a request to get data for an item could use the GET verb
and URL variables to specify a method name and item ID. The resulting
URL string might look like:
http://service.example.com/?method=getItem&id=d3452
To access a REST-style web service with ActionScript, you can
use the URLRequest, URLVariables, and URLLoader classes. In JavaScript
code within an AIR application, you can also use an XMLHttpRequest.
Programming a REST-style web service call in ActionScript, typically
involves the following steps:
-
Create a URLRequest object.
-
Set the service URL and HTTP method verb on the request object.
-
Create a URLVariables object.
-
Set the service call parameters as dynamic properties of
the variables object.
-
Assign the variables object to the data property of the request
object.
-
Send the call to the service with a URLLoader object.
-
Handle the
complete
event dispatched by
the URLLoader that indicates that the service call is complete.
It is also wise to listen for the various error events that can
be dispatched by a URLLoader object.
For example, consider a web service that exposes a test method
that echoes the call parameters back to the requestor. The following
ActionScript code could be used to call the service:
import flash.events.Event;
import flash.events.ErrorEvent;
import flash.events.IOErrorEvent;
import flash.events.SecurityErrorEvent;
import flash.net.URLLoader;
import flash.net.URLRequest;
import flash.net.URLRequestMethod;
import flash.net.URLVariables;
private var requestor:URLLoader = new URLLoader();
public function restServiceCall():void
{
//Create the HTTP request object
var request:URLRequest = new URLRequest( "http://service.example.com/" );
request.method = URLRequestMethod.GET;
//Add the URL variables
var variables:URLVariables = new URLVariables();
variables.method = "test.echo";
variables.api_key = "123456ABC";
variables.message = "Able was I, ere I saw Elba.";
request.data = variables;
//Initiate the transaction
requestor = new URLLoader();
requestor.addEventListener( Event.COMPLETE, httpRequestComplete );
requestor.addEventListener( IOErrorEvent.IOERROR, httpRequestError );
requestor.addEventListener( SecurityErrorEvent.SECURITY_ERROR, httpRequestError );
requestor.load( request );
}
private function httpRequestComplete( event:Event ):void
{
trace( event.target.data );
}
private function httpRequestError( error:ErrorEvent ):void{
trace( "An error occured: " + error.message );
}
In JavaScript within an AIR application, you can make the same
request using the XMLHttpRequest object:
<html>
<head><title>RESTful web service request</title>
<script type="text/javascript">
function makeRequest()
{
var requestDisplay = document.getElementById( "request" );
var resultDisplay = document.getElementById( "result" );
//Create a conveninece object to hold the call properties
var request = {};
request.URL = "http://service.example.com/";
request.method = "test.echo";
request.HTTPmethod = "GET";
request.parameters = {};
request.parameters.api_key = "ABCDEF123";
request.parameters.message = "Able was I ere I saw Elba.";
var requestURL = makeURL( request );
xmlhttp = new XMLHttpRequest();
xmlhttp.open( request.HTTPmethod, requestURL, true);
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {
resultDisplay.innerHTML = xmlhttp.responseText;
}
}
xmlhttp.send(null);
requestDisplay.innerHTML = requestURL;
}
//Convert the request object into a properly formatted URL
function makeURL( request )
{
var url = request.URL + "?method=" + escape( request.method );
for( var property in request.parameters )
{
url += "&" + property + "=" + escape( request.parameters[property] );
}
return url;
}
</script>
</head>
<body onload="makeRequest()">
<h1>Request:</h1>
<div id="request"></div>
<h1>Result:</h1>
<div id="result"></div>
</body>
</html>
