在通过使用FileUpload组件上传的过程中，通过自己的调试，总结如下：
1）使用之前的准备，我用的是commons-fileupload-1.1-dev.jar和commons-io-1.1-dev.jar。
解释一下：尽管有的资料解释是commons-fileupload-1.0-beta.jar和commons-beanutils.jar，通过调试的结果
显示并不是需要commons-beanutils.jar文件，而是由于在parseRequest(request)的类有关继承于DiskFileItem
类。而他有private org.apache.commons.io.output.DeferredFileOutputStream dfos。这样的就必须使用到commons-io-1.1-dev.jar。因此需要导入该包。否则就出classNotFound：.DeferredFileOutputStream的错误。
2）由于涉及文件，就涉及到文件系统。然而在java或应用服务器中对于文件系统的访问，就有一定的安全策略。
需要将下列权限添加到您应用程序服务器的安全策略文件中：
permission java.io.FilePermission "<<ALL FILES>>", "read,write,delete";
具体是添加到..\bea\weblogic81\server\lib\weblogic.policy中的.
否则会可能出如下异常错误：
org.apache.commons.fileupload.FileUploadException:
java.lang.reflect.InvocationTargetException
at
org.apache.commons.fileupload.FileUpload.createItem(FileUpload.java:615)
at
org.apache.commons.fileupload.FileUpload.parseRequest(FileUpload.java:474)
at
org.apache.commons.fileupload.FileUpload.parseRequest(FileUpload.java:355)
....
3）对于不同的服务器，在调试的过程中会出各种不一样的结果。这个与具体的服务器有关。
4）由于FileUpload在不断的更新版本，它的很多方法已经不推荐使用了（这与该组件的不断的改进有关）。通过对最新的帮助文档和网上的资料写了一个标准的程序如下：
fileUpload文件：
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.*;
import java.util.*;
import java.util.regex.*;
import java.io.*;
import org.apache.commons.fileupload.servlet.*;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
/*
* 创建日期 2005-4-10
*
* TODO 要更改此生成的文件的模板，请转至
* 窗口 － 首选项 － Java － 代码样式 － 代码模板
*/
/**
* @author gaolong1
*
* TODO 要更改此生成的类型注释的模板，请转至
* 窗口 － 首选项 － Java － 代码样式 － 代码模板
*/
public class FileUpload extends HttpServlet {
/**
* Destruction of the servlet. <br>
*/
private String uploadPath = "D:\\addnetFile\\"; // 用于存放上传文件的目录
private File tempPath =new File("D:\\addnetFile\\tmp\\"); // 用于存放临时文件的目录
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException{
res.setContentType( "text/html; charset=GB2312");
PrintWriter out=res.getWriter();
System.out.println(req.getContentLength());
System.out.println(req.getContentType());
DiskFileItemFactory factory = new DiskFileItemFactory();
// maximum size that will be stored in memory
factory.setSizeThreshold(4096);
// the location for saving data that is larger than getSizeThreshold()
factory.setRepository(new File("d:\\File\\addnetFile\\temp"));
ServletFileUpload upload = new ServletFileUpload(factory);
// maximum size before a FileUploadException will be thrown
upload.setSizeMax(1000000);
try{
List fileItems = upload.parseRequest(req);
// assume we know there are two files. The first file is a small
// text file, the second is unknown and is written to a file on
// the server
Iterator iter = fileItems.iterator();
// 正则匹配，过滤路径取文件名
String regExp=".+\\\\(.+)$";
// 过滤掉的文件类型
String[] errorType={".exe",".com",".cgi",".asp"};
Pattern p = Pattern.compile(regExp);
while (iter.hasNext()) {
FileItem item = (FileItem)iter.next();
//忽略其他不是文件域的所有表单信息
if (!item.isFormField()) {
String name = item.getName();
long size = item.getSize();
if((name==null||name.equals("")) && size==0)
continue;
Matcher m = p.matcher(name);
boolean result = m.find();
if (result){
for (int temp=0;temp<errorType.length;temp++){
if (m.group(1).endsWith(errorType[temp])){
throw new IOException(name+": wrong type");
}
}
try{
// 保存上传的文件到指定的目录
// 在下文中上传文件至数据库时，将对这里改写
item.write(new File("d:\\" + m.group(1)));
out.print(name+" "+size+"<br>");
}
catch(Exception e){
out.println(e);
}
}
else
{
throw new IOException("fail to upload");
}
}
}
}
catch (IOException e){
out.println(e);
}
catch (FileUploadException e){
out.println(e);
}
// 保存上传的文件到指定的目录
// 在下文中上传文件至数据库时，将对这里改写
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occure
*/
public void init() throws ServletException {
// Put your code here
}
}
对应的请求文件：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>index.html</title>
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="this is my page">
<!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
</head>
<body>
<form action="./servlet/FileUpload" method="post" enctype="multipart/form-data" name="form1">
<input type="file" name="file">
<input type="submit" name="Submit" value="upload">
</form>
<form action="./servlet/HelloWord" method="post">
<input type="submit"/>
</form>
<form name="uploadform" method="POST" action="./servlet/FileUpload" ENCTYPE="multipart/form-data">
<table border="1" width="450" cellpadding="4" cellspacing="2" bordercolor="#9BD7FF">
<tr><td width="100%" colspan="2">
文件1：<input name="x" size="40" type="file">
</td></tr>
<tr><td width="100%" colspan="2">
文件2：<input name="y" size="40" type="file">
</td></tr>
<tr><td width="100%" colspan="2">
文件3：<input name="z" size="40" type="file">
</td></tr>
</table>
<br/><br/>
<table>
<tr><td align="center"><input name="upload" type="submit" value="开始上传"/></td></tr>
</table>
</form>
</body>
</html>
注：该代码由部分来自网上！