Flex HTTPService如何给后台传参数

最近看一些文档,总结了一些<mx:HTTPService>给后台传递参数的方法,列举如下:
方法1:采用URLVariables对象

<?xml version=”1.0″ encoding=”utf-8″?>
<mx:Application xmlns:mx=”http://www.adobe.com/2006/mxml”
     layout=”absolute” fontSize=”12″
    >
    <mx:Script>
        <![CDATA[
            import mx.controls.Alert;
            import mx.rpc.events.ResultEvent;
            //对提交给后台的参数进行UTF-8的编码处理
            private function httpEncoding(param:String):String{
                return encodeURIComponent(param);
            }
            private function httpEncoding0(param:String):String{
                return param;//encodeURI(param);
            }
            private function doRequest():void{
                btn_do.enabled=false;
                var url:String = "http://localhost:8600/grid.jsp";
                //以下那样写后台会乱码,不管是否做URI编码转换
                //url += "?user="+httpEncoding0("用户名");
                //url += "&psw="+httpEncoding0("密码");
                //trace(url);
                srv.url = url;
                //srv.send();
                //以下这样写正常
                var params:URLVariables = new URLVariables();
                //这个user,psw就是传入后台的参数user,jsp就用 request.getParameter("user")来取
                params.user = httpEncoding("用户名");
                params.psw = httpEncoding("密码");
                srv.send(params);            
            }
            private function resultHandler(event:ResultEvent):void{
                Alert.show("与后台交互结束,前台开始取得的数据...","提示信息");
                btn_do.enabled=true;
            }
        ]]>
    </mx:Script>
    <mx:HTTPService id=”srv” result=”resultHandler(event);”/>
    <mx:Panel title=”测试与jsp后台交互” layout=”absolute” width=”100%” height=”90%”>
        <mx:Button id=”btn_do” label=”取得数据” click=”doRequest();”/>
        <mx:Spacer height=”1″/>
        <mx:DataGrid dataProvider=”{srv.lastResult.catalog.product}” width=”100%” height=”100%” y=”28″/>     
    </mx:Panel>
</mx:Application>

方法2:采用<mx:request/>,同时也演示了mx:State的用法

<?xml version=”1.0″ encoding=”utf-8″?>
<mx:Application xmlns:mx=”http://www.adobe.com/2006/mxml” layout=”absolute”>
    <mx:states>
        <mx:State name=”Logged In”>
            <mx:SetProperty target=”{panel1}” name=”width” value=”95%”/>
            <mx:SetProperty target=”{panel1}” name=”height” value=”95%”/>
            <mx:RemoveChild target=”{password}”/>
            <mx:RemoveChild target=”{username}”/>
            <mx:RemoveChild target=”{label1}”/>
            <mx:RemoveChild target=”{Submit}”/>
            <mx:RemoveChild target=”{label2}”/>
            <mx:SetProperty target=”{panel1}” name=”title” value=”Members Section”/>
            <mx:AddChild relativeTo=”{panel1}” position=”lastChild”>
                <mx:Label x=”10″ y=”10″ text=”Welcome to the Members Section!”/>
            </mx:AddChild>
            <mx:AddChild relativeTo=”{panel1}” position=”lastChild”>
                <mx:Label x=”10″ y=”36″ text=”Here you can do great things, like join the forums @ Viper Creations!”/>
            </mx:AddChild>
            <mx:AddChild relativeTo=”{panel1}” position=”lastChild”>
                <mx:Label x=”10″ y=”62″ text=”Label”/>
            </mx:AddChild>
        </mx:State>
    </mx:states>
    <mx:Script>
        <![CDATA[
            import mx.rpc.events.ResultEvent;
            
        ]]>
    </mx:Script>
    <mx:Script>
    
<![CDATA[
private function checkLogin(evt:ResultEvent):void
{
    if(evt.result.loginsuccess == "yes")
    {
    currentState = "Logged In";
    }
    if(evt.result.loginsuccess == "no")
    {
        
        mx.controls.Alert.show('Invalid username/password');
    }        
}
]]>
</mx:Script>
    <mx:HTTPService id=”login_user” result=”checkLogin(event)” showBusyCursor=”true” method=”POST” url=”http://www.vipercreations.com/site_admin/login.php” useProxy=”false”>
        <mx:request xmlns=”">
            <username>
                {username.text}
            </username>
            <password>
                {password.text}
            </password>
        </mx:request>
    </mx:HTTPService>
    
    <mx:Panel resizeEffect=”Resize” width=”250″ height=”200″ layout=”absolute” title=”Login System” horizontalCenter=”0″ verticalCenter=”-2″ id=”panel1″>
        <mx:Label x=”10″ y=”10″ text=”Username:” id=”label1″/>
        <mx:TextInput x=”10″ y=”36″ id=”username”/>
        <mx:Label x=”10″ y=”66″ text=”Password:” id=”label2″/>
        <mx:TextInput x=”10″ y=”92″ id=”password” displayAsPassword=”true”/>
       <mx:Button x=”10″ y=”122″ label=”Submit” id=”Submit” click=”login_user.send();”/>
    </mx:Panel>
    
</mx:Application>

本文参考：冰山上的播客
http://xinsync.xju.edu.cn/index.php/archives/1513