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>