首先，建议将编码设置为GB2312，并在WEB-INFlib里导入：commons-fileupload-1.3.jar和commons-io-2.4.jar，可百度下下载，然后你编码完成后，上传时可能会遇到"servlet Bad version number in .class file"错误。
解决：
1.Window --> Preferences -->Java --> compiler中的compiler compliance level对应的下拉菜单中选择JDK版本.
2.Window --> Preferences -->MyEclipse --> Servers-->Tomcat --> Tomcat n.x -->JDK中的Tomcat JDKname下的下拉菜单中选择自己电脑上安装的JDK版本(必须与步骤1中的JDK版本一致).
如果还是没有解决,不用着急,因为有些MyEclipse版本自带有JDK版本,所以也要将它改过来.
3.Window --> Preferences -->Java -->Installed JRES,然后在右边选择与步骤1和2版本一致的JDK版本,如果没有,可以自己添加.然后选中就可以了.
4、.Window --> Preferences -->MyEclipse --> Servers-Resin 3-Resin 3.x-JDK-Resin jdk name：选择jdk1.6.0_03
接下来，我们来编码，实现多个文件上传
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="GB2312"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<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 style="margin:50px">
<form action="servlet/UploadServlet" method="post" enctype="multipart/form-data">
<p>上传文件：</p>
文件1：<input type="file" name="file1" /><br/>
描述：<input type="text" name="description1" /><br/>
文件2：<input type="file" name="file2" /><br/>
描述：<input type="text" name="description2" /><br/>
<input type="submit" value=" 上 传 " />
</form>
</body>
</html>
com.xieyuan.ServletUpload.java
package com.xieyuan;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.sound.sampled.AudioFormat.Encoding;
import org.apache.commons.fileupload.DiskFileUpload;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class UploadServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public UploadServlet() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @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 doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("GB2312");
response.getWriter().println("<script>alert('请用POST方式上传文件！')</script>");
}
/**
* 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 request, HttpServletResponse response)
throws ServletException, IOException {
File file=null;
String description=null;
String uploadPath=this.getServletContext().getRealPath("upload");
String uploadTemp=this.getServletContext().getRealPath("upload/temp");
//设置响应格式（不设置请求格式，因为文件是二进制的，不能使用UTF-8格式化）
response.setContentType("text/html;charset=gb2312");
PrintWriter out=response.getWriter();
out.println("<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">");
out.println("<HTML>");
out.println("<HEAD><TITLE>文件上传</TITLE></HEAD>");
out.println("<BODY style='margin:50px'>");
out.println("上传日志：<BR/>");
//创建基于磁盘的工厂，针对大文件，临时文件将存储在磁盘
DiskFileItemFactory factory=new DiskFileItemFactory();
//设置缓冲区大小,超出该文件直接写入到磁盘的大小设置门槛。
factory.setSizeThreshold(10240); //这里默认10KB
//设置用于大于配置的大小阈值设置的临时存储文件目录。
factory.setRepository(new File(uploadTemp));
//创建一个文件上传的句柄
ServletFileUpload upload=new ServletFileUpload(factory);
//设置最大文件尺寸 ，这里是4MB
upload.setSizeMax(4194304);
upload.setHeaderEncoding("GB2312");
try {
//将解析结果放在LIST中
List<FileItem> list =upload.parseRequest(request);
out.println("遍历所有的 FileItem ... <br/>");
// 遍历 list 中所有的 FileItem
for(FileItem item:list)
{
// 如果是 文本域
if(item.isFormField())
{
if(item.getFieldName().equals("description1")||item.getFieldName().equals("description2"))
{
description = item.getString("GB2312");
out.println("遍历到 "+item.getFieldName()+" ... <br/>"+description+"<BR/>");
}
}
else
{
//否则为文件域,当getName为Null说明没有选则文件
if((item.getFieldName().equals("file1")||item.getFieldName().equals("file2"))
&&item.getName()!=null&&!item.getName().equals(""))
{
try
{
File remoteFile=new File(item.getName());
out.println("遍历到 file ... <br/>");
out.println("客户端文件位置: " + remoteFile.getAbsolutePath() + "<br/>");
// 服务器端文件，放在 upload 文件夹下
file=new File(uploadPath,remoteFile.getName());
if(!file.getParentFile().exists())
file.getParentFile().mkdirs();
if(!file.exists())
file.createNewFile();
item.write(file);
} catch (Exception e) {
}
finally //总是立即删除保存表单字段内容的临时文件
{
item.delete();
}
}
}
}
out.println("Request 解析完毕,文件上传完毕！");
} catch (Exception e) {
out.println("Request 解析异常！"+e.getMessage());
}
out.flush();
out.close();
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>UploadServlet</servlet-name>
<servlet-class>com.xieyuan.UploadServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>UploadServlet</servlet-name>
<url-pattern>/servlet/UploadServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
这样上传文件不会乱码。深入参看，剖析Commons-fileupload.jar上传原理，解决中文乱码原因，请看：
http://download.csdn.net/detail/ab6326795/6219065
张孝祥写的