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June 10, 2009

Flex with Ajax

The Flex Ajax Bridge (FABridge) is a small code library that you can insert into an Flex application, a Flex component, or an empty SWF file to expose it to scripting in the browser.

Rather than having to define new, simplified APIs to expose a graph of ActionScript objects to JavaScript, with FABridge you can make your ActionScript classes available to JavaScript without any additional coding. After you insert the library, essentially anything you can do with ActionScript, you can do with JavaScript.

Adobe Flash Player has the native ability, through the External API (the ExternalInterface class), to call JavaScript from ActionScript, and vice versa. But ExternalInterface has some limitations:

  • The ExternalInterface class requires you, the developer, to write a library of extra code in both ActionScript and JavaScript, to expose the functionality of your Flex application to JavaScript, and vice versa.
  • The ExternalInterface class also limits what you can pass across the gap - primitive types, arrays, and simple objects are legal, but user-defined classes, with associated properties and methods, are off-limits.
  • The ExternalInterface class lets you define an interface so your JavaScript can call your ActionScript. FABridge lets you write JavaScript instead of ActionScript.

When to use the Flex Ajax Bridge

The FABridge library is useful in the following situations:

  • You want to use a rich Flex component in an Ajax application but do not want to write a lot of Flex code. If you wrap the component in a FABridge-enabled stub application, you can script it entirely from JavaScript, including using JavaScript generated remotely by the server.
  • You have only one or two people on your team who know Flex. The FABridge library lets everyone on your team use the work produced by one or two Flex specialists.
  • You are building an integrated rich Internet application (RIA) with Flex and Ajax portions.Although you could build the integration yourself using ExternalInterface, you might find it faster to start with the FABridge.

Requirements for using the Ajax Bridge

To use the FABridge library and samples, you must have the following:

  • Flex Ajax Bridge, which is included in the following directory of the Flex 3 SDK installation:


  • Adobe Flex SDK
  • Adobe® Flash® Player 9 or Adobe® AIR™
  • Microsoft Internet Explorer, Mozilla Firefox, or Opera with JavaScript enabled
  • Any HTTP server to run the samples

To run the samples:

  1. Browse to the files found within the installation_dir\frameworks\javascript\fabridge
  2. Place the src and samples folders side by side on any HTTP server.
  3. Open a web browser to http://yourwebserver/samples/FABridgeSample.html and samples/SimpleSample.html and follow the instructions there. Make sure you access the samples through http:// URLs and not file:// URLs. The Flash Player security sandbox prevents them from working correctly when they are accessed as local files.

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