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。
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??? 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：
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??? 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。
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??? B、利用webService的方式来进行文件的上传和下载
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??? C、利用flex+sevlet+fileupload组件实现文件的上传和下载
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??? 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）：
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??? 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
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??? 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
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??? 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。
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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()
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??????? 代码如下：
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??? /** *//**
???? * 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
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<?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"/>
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</mx:TitleWindow>
??? 2、JAVA端
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???? 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;
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import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
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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;
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public class FileUploadServlet extends HttpServlet
{
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??? // private String uploadPath = "D:upload";
??? private String path = "file_path.properties";
??? private String skStr = "";
??? private String uploadPath = "";
??? private int maxPostSize = 1000 * 1024 * 1024;
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??? public void doPost(HttpServletRequest req,HttpServletResponse res) throws ServletException,
??????????? IOException
??? {
??????? String filePathaa = this.getServletConfig().getServletContext().getRealPath("/");
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??????? Properties p = loadProperties(path);
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??????? uploadPath = p.getProperty("filepath");
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??????? res.setContentType("text/html;charset=UTF-8");
??????? req.setCharacterEncoding("UTF-8");
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??????? DiskFileItemFactory factory = new DiskFileItemFactory();
??????? factory.setSizeThreshold(1024*20);
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??????? 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();
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??????????????????? try
??????????????????? {
??????????????????????? File skFile = new File(uploadPath + name);
??????????????????????? if (skFile.exists())
??????????????????????? {
??????????????????????????? skFile.delete();
??????????????????????????? item.write(new File(uploadPath + name));
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??????????????????????? }
??????????????????????? else
??????????????????????? {
??????????????????????????? item.write(new File(uploadPath + name));
??????????????????????? }
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??????????????????? } catch (Exception e)
??????????????????? {
??????????????????????? e.printStackTrace();
??????????????????? }
??????????????? }
??????????? }
??????? } catch (FileUploadException e)
??????? {
??????????? e.printStackTrace();
??????? }
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??? }
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??? public Properties loadProperties(String path) throws IOException
??? {
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??????? InputStream in = this.getClass().getResourceAsStream(path);
??????? //
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??????? Properties p = new Properties();
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??????? p.load(in);
??????? in.close();
??????? return p;
??? }
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}
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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>
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??? <servlet-mapping>
??????? <servlet-name>FileUploadServlet</servlet-name>
??????? <url-pattern>/FileUploadServlet</url-pattern>
??? </servlet-mapping>
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二、文件的下载
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??? 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。
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???? 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;
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import flash.net.FileReferenceList;
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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);
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??? }
???
??? private function completeHandler(event:Event):void {
??? mx.controls.Alert.show("文件下载成功");
??? }
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这里的是上面上传代码的上部分
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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"/>
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??? <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>
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