Web service requests

There are a variety of HTTP-based web services. The main types include:

REST
XML-RPC
SOAP

To use a web service in ActionScript 3, you create a URLRequest object, construct the web service call using either URL variables or an XML document, and send the call to the service using a URLLoader object. The Flex framework contains several classes that make it easier to use web services—especially useful when accessing complex SOAP services. Starting with Flash Professional CS3, you can use the Flex classes in applications developed with Flash Professional as well as in applications developed in Flash Builder.

In HTML-based AIR applications, you can use either the URLRequest and URLLoader classes or the JavaScript XMLHttpRequest class. If desired, you can also create a SWF library that exposes the web service components of the Flex framework to your JavaScript code.

When your application runs in a browser, you can only use web services in the same Internet domain as the calling SWF unless the server hosting the web service also hosts a cross-domain policy file that permits access from other domains. A technique that is often used when a cross-domain policy file is not available is to proxy the requests through your own server. Adobe Blaze DS and Adobe LiveCycle support web service proxying.

In AIR applications, a cross-domain policy file is not required when the web service call originates from the application security sandbox. AIR application content is never served from a remote domain, so it cannot participate in the types of attacks that cross-domain policies prevent. In HTML-based AIR applications, content in the application security sandbox can make cross-domain XMLHttpRequests. You can allow content in other security sandboxes to make cross-domain XMLHttpRequests as long as that content is loaded into an iframe.