flex---->HttpService

Flex中如何利用HTTPService的send()，将参数传递给HTTPService

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
				layout="vertical"
				verticalAlign="middle"
				backgroundColor="white" viewSourceURL="srcview/index.html">
	
	<mx:Script>
		<![CDATA[
			import mx.controls.Alert;
			import mx.events.ValidationResultEvent;
			import mx.utils.StringUtil;
			
			private function submit_click(evt:MouseEvent):void {
				var result:ValidationResultEvent = stringValidator.validate();
				var params:Object = {};
				
				lbl.text = "";
				
				switch (result.type) {
					case ValidationResultEvent.INVALID:
						Alert.show(result.message, result.type);
						break;
					case ValidationResultEvent.VALID:
						params["name"] = StringUtil.trim(firstName.text);
						httpServ.send(params);
						break;
				}
			}
		]]>
	</mx:Script>
	
	<mx:StringValidator id="stringValidator"
						source="{firstName}"
						property="text"
						minLength="2"
						maxLength="{firstName.maxChars}" />
	
	<mx:HTTPService id="httpServ">
		<mx:resultFormat>flashvars</mx:resultFormat>
		<mx:url>http://www.flash-mx.com/mm/greeting.cfm</mx:url>
		<mx:result>lbl.text = httpServ.lastResult.welcomeMessage;</mx:result>
		<mx:fault>Alert.show(event.toString(), event.type);</mx:fault>
	</mx:HTTPService>
	
	<mx:ApplicationControlBar dock="true">
		<mx:Form>
			<mx:FormItem label="Name:" required="true"
						 direction="horizontal">
				<mx:TextInput id="firstName"
							  maxChars="20" />
				<mx:Button label="Submit"
						   click="submit_click(event);" />
			</mx:FormItem>
		</mx:Form>
	</mx:ApplicationControlBar>
	
	<mx:Label id="lbl" fontSize="32" />
	
</mx:Application>