Flex和后台程序通信（HttpService）

<?xml version="1.0" encoding="utf-8"?>
<mx:Application 
    xmlns:mx="http://www.adobe.com/2006/mxml" 
    layout="absolute" initialize="initializeHandler(event)">
    <mx:Script>
        <![CDATA[
            private function initializeHandler(event:Event):void
            {
                countriesService.send();
            }

            private function changeHandler(event:Event):void
            {
                statesService.send();
            }
        ]]>
    </mx:Script>
    <mx:HTTPService id="countriesService" 
        url="http://www.rightactionscript.com/states/xml/countries.xml"/>
    <mx:HTTPService id="statesService" 
        url="http://www.rightactionscript.com/states/xml/states.php">
        <mx:request>
            <country>
                {country.value}
            </country>
        </mx:request>
    </mx:HTTPService>
    <mx:VBox>
        <mx:ComboBox id="country" 
            dataProvider="{countriesService.lastResult.countries.country}"
            change="changeHandler(event)"/>
        <mx:ComboBox 
            dataProvider="{statesService.lastResult.states.state}"/>
    </mx:VBox>
</mx:Application>

来源：http://blog.youkuaiyun.com/loki_wuxi/archive/2008/05/22/2469597.aspx