Flex与服务器交互之一（URLRequest +URLLoader应用） .

  由于Flex只是一种客户端技术其本身并不能直接同数据库交互，在实际的应用开发过程中Flex提供了如URLRequest、HTTPService、RemoteObject、WebService等类以实现同服务器的通讯和数据交互，下面做一些介绍和实例解析:
   1、使用URLRequest向服务器发送请求，使用URLLoader接收服务器返回的数据:
    URLRequest类可捕获单个 HTTP 请求中的所有信息，可以将 URLRequest 对象传递给 Loader、URLStream 和 URLLoader 类以及其他加载操作的 load() 方法以启动 URL 下载;默认情况下，传递给 url 参数的 URL 必须与执行调用的 SWF 文件在完全相同的域，包括子域。如果要从其它域中加载数据，请在承载数据的服务器上放置一个跨域策略文件。有关URLRequest详细可参看http://help.adobe.com/zh_CN/AIR/1.1/jslr/flash/net/URLRequest.html
   URLVariables类主要用来在应用程序和服务器之间传输参数变量;详细查看:http://livedocs.adobe.com/flex/3_cn/langref/flash/net/URLVariables.html
   URLLoader 类以文本、XML、二进制数据或 URL 编码变量的形式从 URL 返回请求的数据详细请参看:http://livedocs.adobe.com/flex/3_cn/langref/flash/net/URLLoader.html

    完成以下示例要引用到的Flex包:

import mx.rpc.events.FaultEvent;
import mx.collections.XMLListCollection;
import flash.net.URLLoader;
import flash.net.URLRequest;
import flash.net.URLVariables;
import flash.net.URLRequestMethod;
import flash.events.Event;
import mx.utils.URLUtil;
import mx.collections.ArrayCollection;
import mx.rpc.events.ResultEvent;
import com.adobe.serialization.json.JSON;

    import mx.rpc.events.FaultEvent;
    import mx.collections.XMLListCollection;
    import flash.net.URLLoader;
    import flash.net.URLRequest;
    import flash.net.URLVariables;
    import flash.net.URLRequestMethod;
    import flash.events.Event;
    import mx.utils.URLUtil;
    import mx.collections.ArrayCollection;
    import mx.rpc.events.ResultEvent;
    import com.adobe.serialization.json.JSON;

   2、应用示例一：通过URLRequest和URLVariables向服务器发送参数请求并返回服务器文本数据（以下服务器端都采用asp.net编写）
   服务器端代码:

protected void Page_Load(object sender, EventArgs e)
{
        //获取URLResuest请求回的参数 返回数据用；分隔以方便Flex对数据进行序列化
        string rs = String.Format("name={0};age={1};address={2}",Request.QueryString["name"],
                                                                 Request.QueryString["age"],
                                                                 Request.QueryString["address"]);
        Response.ClearContent();
        Response.ContentType = "text/plain";
        Response.Write(rs); //以文本形式返回数据
        Response.End();
}

    protected void Page_Load(object sender, EventArgs e)
    {
            //获取URLResuest请求回的参数 返回数据用；分隔以方便Flex对数据进行序列化
            string rs = String.Format("name={0};age={1};address={2}",Request.QueryString["name"],
                                                                     Request.QueryString["age"],
                                                                     Request.QueryString["address"]);
            Response.ClearContent();
            Response.ContentType = "text/plain";
            Response.Write(rs); //以文本形式返回数据
            Response.End();
    }

   FLEX中发送请求：

private function getText():void
{
    var v:URLVariables = new URLVariables("name=jacky&age=35&address=HongKong China");
    var r:URLRequest = new URLRequest();
    r.url = "http://localhost:2222/FlexService/TextFrm.aspx";
    r.method = URLRequestMethod.GET;
    r.data = v;

    var l:URLLoader = new URLLoader();
    l.load(r);
    l.addEventListener(Event.COMPLETE,txtCompleteHandler); //注册请求完成后 响应获取数据事件方法
    labMsg.alpha = 1;
}

    private function getText():void
    {
        var v:URLVariables = new URLVariables("name=jacky&age=35&address=HongKong China");
        var r:URLRequest = new URLRequest();
        r.url = "http://localhost:2222/FlexService/TextFrm.aspx";
        r.method = URLRequestMethod.GET;
        r.data = v;
       
        var l:URLLoader = new URLLoader();
        l.load(r);
        l.addEventListener(Event.COMPLETE,txtCompleteHandler); //注册请求完成后 响应获取数据事件方法
        labMsg.alpha = 1;
    }

   Flex中接收返回数据

   private function txtCompleteHandler(e:Event):void
{
    var l:URLLoader = URLLoader(e.target);
    var o:Object = URLUtil.stringToObject(String(l.data)); //使用URLUtil对将数据进行反序列化以方便使用
    txtName.text = o.name;
    txtAge.text = o.age;
    txtAddress.text = o.address;
    labMsg.alpha = 0;
}

       private function txtCompleteHandler(e:Event):void
    {
        var l:URLLoader = URLLoader(e.target);
        var o:Object = URLUtil.stringToObject(String(l.data)); //使用URLUtil对将数据进行反序列化以方便使用
        txtName.text = o.name;
        txtAge.text = o.age;
        txtAddress.text = o.address;
        labMsg.alpha = 0;
    }

   3、应用示例二：返回JSON格式数据：
   服务器端代码:
    

public partial class JsonFrm : System.Web.UI.Page
    {
        Person person;
        protected void Page_Load(object sender, EventArgs e)
        {
            person = new Person();
            person.Name = "YAO MING";
            person.Age = 29;
            person.Address = "ShangHai China";
            HttpContext.Current.Response.ClearContent();
            HttpContext.Current.Response.ContentType = "text/plain";
            System.Runtime.Serialization.Json.DataContractJsonSerializer dcjs = new System.Runtime.Serialization.Json.DataContractJsonSerializer(person.GetType());
            dcjs.WriteObject(HttpContext.Current.Response.OutputStream,person);
            HttpContext.Current.Response.End();
        }
    }
    [System.Runtime.Serialization.DataContract]
    public class Person
    {
        [System.Runtime.Serialization.DataMember]
        public String Name{get;set;}
        [System.Runtime.Serialization.DataMember]
        public int Age { get; set; }
        [System.Runtime.Serialization.DataMember]
        public String Address { get; set; }
    }

public partial class JsonFrm : System.Web.UI.Page
    {
        Person person;
        protected void Page_Load(object sender, EventArgs e)
        {
            person = new Person();
            person.Name = "YAO MING";
            person.Age = 29;
            person.Address = "ShangHai China";
            HttpContext.Current.Response.ClearContent();
            HttpContext.Current.Response.ContentType = "text/plain";
            System.Runtime.Serialization.Json.DataContractJsonSerializer dcjs = new System.Runtime.Serialization.Json.DataContractJsonSerializer(person.GetType());
            dcjs.WriteObject(HttpContext.Current.Response.OutputStream,person);
            HttpContext.Current.Response.End();
        }
    }
    [System.Runtime.Serialization.DataContract]
    public class Person
    {
        [System.Runtime.Serialization.DataMember]
        public String Name{get;set;}
        [System.Runtime.Serialization.DataMember]
        public int Age { get; set; }
        [System.Runtime.Serialization.DataMember]
        public String Address { get; set; }
    }

   FLEX中发送请求：
   

private function getJson():void
    {
        var v:URLVariables = new URLVariables();
        var r:URLRequest = new URLRequest();
        r.url = "http://localhost:2222/FlexService/JsonFrm.aspx";
        r.method = URLRequestMethod.GET;
        r.data = v;

        var l:URLLoader = new URLLoader();
        l.load(r);
        l.addEventListener(Event.COMPLETE,jsonCompleteHandler);
        labMsg.alpha = 1;
    }

private function getJson():void
    {
        var v:URLVariables = new URLVariables();
        var r:URLRequest = new URLRequest();
        r.url = "http://localhost:2222/FlexService/JsonFrm.aspx";
        r.method = URLRequestMethod.GET;
        r.data = v;
       
        var l:URLLoader = new URLLoader();
        l.load(r);
        l.addEventListener(Event.COMPLETE,jsonCompleteHandler);
        labMsg.alpha = 1;
    }

   Flex中接收返回数据
  

public function jsonCompleteHandler(e:Event):void
  {
      var l:URLLoader = e.target as URLLoader;
      var o:* = JSON.decode(l.data);

      txtName.text = o.Name;
      txtAge.text = o.Age;
      txtAddress.text = o.Address;
      labMsg.alpha = 0;
  }

  public function jsonCompleteHandler(e:Event):void
    {
        var l:URLLoader = e.target as URLLoader;
        var o:* = JSON.decode(l.data);
       
        txtName.text = o.Name;
        txtAge.text = o.Age;
        txtAddress.text = o.Address;
        labMsg.alpha = 0;
    }

  4、应用示例三：返回XML格式数据：
  服务器端代码:

protected void Page_Load(object sender, EventArgs e)
  {
      String s = @"<?xml version=""1.0"" encoding=""utf-8""?>
                      <EV_ChartData_Scatter xmlns=""http://www.byd.com/ChartData/XML"">
                        <ScatterItem id=""0"">
                          <CAN_ITEM_ID>561</CAN_ITEM_ID>
                          <CAN_ITEM_NAME>主控ECU通讯状况</CAN_ITEM_NAME>
                          <ITEM_VALUE>0</ITEM_VALUE>
                          <MATCH_VALUE>正常</MATCH_VALUE>
                         </ScatterItem>
                        <ScatterItem  id=""1"">
                          <CAN_ITEM_ID>561</CAN_ITEM_ID>
                          <CAN_ITEM_NAME>主控ECU通讯状况</CAN_ITEM_NAME>
                          <ITEM_VALUE>1</ITEM_VALUE>
                          <MATCH_VALUE>丢包</MATCH_VALUE>
                        </ScatterItem>
                      </EV_ChartData_Scatter>";
      Response.ClearContent();
      Response.ContentType = "text/xml";
      Response.Write(s);
      Response.End();
  }

      protected void Page_Load(object sender, EventArgs e)
        {
            String s = @"<?xml version=""1.0"" encoding=""utf-8""?>
                            <EV_ChartData_Scatter xmlns=""http://www.byd.com/ChartData/XML"">
                              <ScatterItem id=""0"">
                                <CAN_ITEM_ID>561</CAN_ITEM_ID>
                                <CAN_ITEM_NAME>主控ECU通讯状况</CAN_ITEM_NAME>
                                <ITEM_VALUE>0</ITEM_VALUE>
                                <MATCH_VALUE>正常</MATCH_VALUE>
                               </ScatterItem>
                              <ScatterItem  id=""1"">
                                <CAN_ITEM_ID>561</CAN_ITEM_ID>
                                <CAN_ITEM_NAME>主控ECU通讯状况</CAN_ITEM_NAME>
                                <ITEM_VALUE>1</ITEM_VALUE>
                                <MATCH_VALUE>丢包</MATCH_VALUE>
                              </ScatterItem>
                            </EV_ChartData_Scatter>";
            Response.ClearContent();
            Response.ContentType = "text/xml";
            Response.Write(s);
            Response.End();
        }

   FLEX中发送请求：
   

private function getXML():void
    {
        var v:URLVariables = new URLVariables();
        var r:URLRequest = new URLRequest();
        r.url = "http://localhost:2222/FlexService/XMLFrm.aspx";
        r.method = URLRequestMethod.GET;
        r.data = v;

        var l:URLLoader = new URLLoader();
        l.load(r);
        l.addEventListener(Event.COMPLETE,xmlCompleteHandler);
    }

private function getXML():void
    {
        var v:URLVariables = new URLVariables();
        var r:URLRequest = new URLRequest();
        r.url = "http://localhost:2222/FlexService/XMLFrm.aspx";
        r.method = URLRequestMethod.GET;
        r.data = v;
       
        var l:URLLoader = new URLLoader();
        l.load(r);
        l.addEventListener(Event.COMPLETE,xmlCompleteHandler);
    }

   Flex中接收返回数据

[Bindable]
        private var xml:XML;
        private function xmlCompleteHandler(e:Event):void
        {
            var l:URLLoader = e.target as URLLoader;
            xml= new XML(l.data);
            for each(var v in xml.ScatterItem)
            {

            }
            labMsg.alpha = 0;
        }