利用flex+sevlet+fileupload组件实现文件的上传和下载

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()

/** *//**
* 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>