和传统的JSP一样，在flex中，有的时候也需要实现文件上传和下载的功能，但是在flex里文件的上传和下载的实现相对来说比较复杂，如何实现，请看下面。
??? 由于flex是一个比较新的技术，在研究的时候，还是按着JSP的方式去尝试，在开始之初，主要有以下几种思路：
????A、利用ftp的方式进行文件的上传和下载，需要利用flex的socket接口。
????B、利用webService的方式来进行文件的上传和下载
????C、利用flex+sevlet+fileupload组件实现文件的上传和下载
??? 在通过比较后，最后选择了第三种，用Flex+sevlet的方式来完成文件上传和下载的功能，理由如下（与上面的思路相对应）：
????A、涉及到了流的操作，实现起来比较复杂，出现错误的几率比较高
????B、关于flex端的可参考的资料比较少，并且还需要启动webservice服务
????C、这个技术比较成熟，从flex2.0开始，在flex端已经可以引用FileReference类了，并且在java端有成熟的组件可以使用，所以最后考虑使用该种方法来处理。
一、文件的上传
????1、Flex端
????????A、使用到的类介绍：
????????????FileReference 类提供了在用户计算机和服务器之间上载和下载文件的方法。 操作系统对话框会提示用户选择要上载的文件或用于下载的位置。它主要能实现一个文件的上传。
????????????FileReferenceList 类提供了让用户选择一个或多个要上载的文件的方法。 FileReferenceList 对象将用户磁盘上的一组本地文件（一个或多个文件）表示为 FileReference 对象的数组。
????????B、使用 FileReferenceList 类 实现多文件上传：
????????????1) 将该类实例化：var myFileRef = new FileReferenceList();?
????????????2) 调用 FileReferenceList.browse() 方法，该方法将打开一个对话框，让用户选择一个或多个要上载的文件：myFileRef.browse();?
????????????3) 在成功调用 browse() 方法之后，使用 FileReference 对象数组来填充 FileReferenceList 对象的 fileList 属性。?
????????????????对 fileList 数组中的每个元素调用 FileReference.upload()
????????代码如下：
????
/**?*/
/**
?????*?执行上传操作
?????*?*/
????
????
private
?function?upLoadFiles():
void
????
{
????????try
????????
{
????????????selectFileList.browse(new?Array(imageFilter,?textFilter));
????????????selectFileList.addEventListener(Event.SELECT,?selectHandler1);
????????}
????????catch?(error:Error)?
????????
{
????????????Alert.show("文件选择出现错误，请选择正确的文件");
????????}
????}
????
/**?*/
/**
?????*?如果文件被选中,则执行该方法
?????*?*/
????function?selectHandler1(event:Event):
void
????
{
????????var?request:URLRequest?=?new?URLRequest("FileUploadServlet");
????????var?upLoadFile:FileReference;?
????????var?upLoadFileList:FileReferenceList?=?FileReferenceList(event.target);
????????var?selectedFileArray:Array?=?upLoadFileList.fileList;
????????login?=(testPress)(PopUpManager.createPopUp(?this,?testPress?,?true));
????????for?(var?i:uint?=?0;?i?<?selectedFileArray.length;?i++)
????????
{?
????????????upLoadFile?=?FileReference(selectedFileArray[i]);
????????????upLoadFile.addEventListener(Event.COMPLETE,?UpLoadcompleteHandler);
????????????upLoadFile.addEventListener(ProgressEvent.PROGRESS,?progressHandler);?
????????????try
????????????
{
????????????????upLoadFile.upload(request);
????????????}
????????????catch?(error:Error)
????????????
{
????????????????Alert.show(error.message.toString());
????????????}
????????}
????}
????function?UpLoadcompleteHandler(event:Event):
void
????
{
?????????var?upLoadFiles:FileReference?=?FileReference(event.target);
?????????var?fileNames?=?upLoadFiles.name;
?????????//Alert.show('文件'+fileNames+'上传成功')
?????????login.myLabels.text?=?'文件'+fileNames+'上传成功';
????}
?????
private
?function?progressHandler(e:ProgressEvent):
void
??
{?
????var?proc:?uint?=?e.bytesLoaded?/?e.bytesTotal?*?100;??
????login.bar.setProgress(proc,?100);??
????login.bar.label=?"当前进度:?"?+?"?"?+?proc?+?"%";??
?}
?
testPress.mxml
<?
xml?version="1.0"?encoding="utf-8"
?>
<
mx:TitleWindow?
xmlns:mx
="http://www.adobe.com/2006/mxml"
?layout
="absolute"
?width
="528"
?height
="236"
>
<
mx:Script
>
????
<![CDATA[
????????import?mx.managers.PopUpManager;
????????public?function?clickMe():void?{
????????????PopUpManager.removePopUp(this);
????????}
????
]]>
</
mx:Script
>
????
<
mx:ProgressBar?
id
="bar"
?labelPlacement
="bottom"
?themeColor
="#F20D7A"
??
minimum
="0"
?visible
="true"
?maximum
="100"
?label
="当前进度:?0%"
??
direction
="right"
?mode
="manual"
?width
="200"
?x
="154"
?y
="84"
/>
??
????
<
mx:Button?
x
="221"
?y
="135"
?label
="关闭"
?click?
=?"clickMe();"
/>
????
<
mx:Label?
x
="173"
?y
="27"
?id
="myLabels"
?width
="157"
/>
</
mx:TitleWindow
>
????2、JAVA端
?????接受Flex端的请求，在JAVA端利用apache的fileupload类库实现上传功能。代码如下：
import
?java.io.File;
import
?java.io.FileInputStream;
import
?java.io.IOException;
import
?java.io.InputStream;
import
?java.util.Iterator;
import
?java.util.List;
import
?java.util.Properties;
import
?javax.servlet.ServletContext;
import
?javax.servlet.ServletException;
import
?javax.servlet.http.HttpServlet;
import
?javax.servlet.http.HttpServletRequest;
import
?javax.servlet.http.HttpServletResponse;
import
?org.apache.commons.fileupload.FileItem;
import
?org.apache.commons.fileupload.FileUploadException;
import
?org.apache.commons.fileupload.disk.DiskFileItemFactory;
import
?org.apache.commons.fileupload.servlet.ServletFileUpload;
public
?
class
?FileUploadServlet?
extends
?HttpServlet
{
????//?private?String?uploadPath?=?"D:upload";
????private?String?path?=?"file_path.properties";
????private?String?skStr?=?"";
????private?String?uploadPath?=?"";
????private?int?maxPostSize?=?1000?*?1024?*?1024;
????public?void?doPost(HttpServletRequest?req,?HttpServletResponse?res)?throws?ServletException,
????????????IOException
????
{
????????String?filePathaa?=?this.getServletConfig().getServletContext().getRealPath("/");
????????Properties?p?=?loadProperties(path);
????????uploadPath?=?p.getProperty("filepath");
????????res.setContentType("text/html;charset=UTF-8");
????????req.setCharacterEncoding("UTF-8");
????????DiskFileItemFactory?factory?=?new?DiskFileItemFactory();
????????factory.setSizeThreshold(1024*20);
????????ServletFileUpload?upload?=?new?ServletFileUpload(factory);
????????upload.setSizeMax(maxPostSize);
????????try
????????
{
????????????List?fileItems?=?upload.parseRequest(req);
????????????Iterator?iter?=?fileItems.iterator();
????????????while?(iter.hasNext())
????????????
{
????????????????FileItem?item?=?(FileItem)?iter.next();
????????????????if?(!item.isFormField())
????????????????
{
????????????????????String?name?=?item.getName();
????????????????????try
????????????????????
{
????????????????????????File?skFile?=?new?File(uploadPath?+?name);
????????????????????????if?(skFile.exists())
????????????????????????
{
????????????????????????????skFile.delete();
????????????????????????????item.write(new?File(uploadPath?+?name));
????????????????????????}
????????????????????????else
????????????????????????
{
????????????????????????????item.write(new?File(uploadPath?+?name));
????????????????????????}
????????????????????}?catch?(Exception?e)
????????????????????
{
????????????????????????e.printStackTrace();
????????????????????}
????????????????}
????????????}
????????}?catch?(FileUploadException?e)
????????
{
????????????e.printStackTrace();
????????}
????}
????public?Properties?loadProperties(String?path)?throws?IOException
????
{
????????InputStream?in?=?this.getClass().getResourceAsStream(path);
????????//
????????Properties?p?=?new?Properties();
????????p.load(in);
????????in.close();
????????return?p;
????}
}
还要修正web.xml，添加如下内容
<!--
?For?file?uploaded?
-->
???
<
servlet
>
????????
<
servlet-name
>
FileUploadServlet
</
servlet-name
>
????????
<
servlet-class
>
FileUploadServlet
</
servlet-class
>
????
</
servlet
>
????
<
servlet-mapping
>
????????
<
servlet-name
>
FileUploadServlet
</
servlet-name
>
????????
<
url-pattern
>
/FileUploadServlet
</
url-pattern
>
????
</
servlet-mapping
>
二、文件的下载
????
????调用的方法：private function downLoadFiles(urlAdd:String):void
????参数urlAdd就是用户的ip地址，如果使用本地的localhost就会产生安全沙箱问题，因此让用户自己输入自己的ip地址。这样就避免了安全沙箱的问题。如果是本机启动服务，访问地址，需要输入IP，不能用localhost来代替本机的IP地址，否则，还是会出现安全沙箱问题。
?????FileReference.download() 方法提示用户提供文件的保存位置并开始从远程 URL 进行下载。直接加载请求路径下载，不需要后台的支持。代码如下：
import
?com.systex.flex.util.testPress;
import
?flash.net.FileReferenceList;
import
?mx.controls.Alert;
import
?mx.managers.PopUpManager;
????var?imageFilter:FileFilter?
=
?
new
?FileFilter(
"
Image?Files?(*.jpg,?*.jpeg,?*.gif,?*.png)
"
,?
"
*.jpg;?*.jpeg;?*.gif;?*.png
"
);
????var?textFilter:FileFilter?
=
?
new
?FileFilter(
"
Text?Files?(*.txt,?*.rtf,?*.zip)
"
,?
"
*.txt;?*.rtf;?*.zip
"
);
????var?selectFileList:FileReferenceList?
=
?
new
?FileReferenceList();
????var?selectedFileArray:Array?
=
?
new
?Array();
????var?login:testPress?
=
?
new
?testPress();
????var?downloadURL:URLRequest;
????var?DownLoadfile:FileReference;?
//
这是要主要的地方
????
//
http://
XX.XX.XX.XX:8080/upload/main.zip
????
private
?function?downLoadFiles(urlAdd:String):
void
????
{
????????downloadURL?=?new?URLRequest(urlAdd);
????????DownLoadfile?=?new?FileReference();
????????configureListeners(DownLoadfile);
????????DownLoadfile.download(downloadURL);
????}
?????
private
?function?configureListeners(dispatcher:IEventDispatcher):
void
?
{
????????dispatcher.addEventListener(Event.COMPLETE,?completeHandler);
????}
????
????
private
?function?completeHandler(event:Event):
void
?
{
????mx.controls.Alert.show("文件下载成功");
????}
这里的是上面上传代码的上部分
附上测试的MXML
<?
xml?version="1.0"?encoding="utf-8"
?>
<
mx:Application?
xmlns:mx
="http://www.adobe.com/2006/mxml"
?layout
="absolute"
????
>
<
mx:Script?
source
="UpDownLoadFiles.as"
/>
????
<
mx:Canvas?
width
="100%"
?height
="100%"
?x
="10"
?y
="170"
?fontSize
="15"
>
????
<
mx:VBox?
width
="100%"
?horizontalAlign
="center"
>
????
<
mx:TextInput?
id
="mytextInput"
/>
????
<
mx:Button?
label
="文件下载"
?click
="downLoadFiles('http://'+mytextInput.text+':8080/downLoading/2MSN.rar');"
/>
????
<
mx:Button?
label
="上传文件"
?click
="upLoadFiles();"
/>
????
</
mx:VBox
>
????
</
mx:Canvas
>
</
mx:Application
>
fileupload下载地址
