常用的上传组件：
Apache 的 Commons FileUpload
jspSmartUpload
JavaZoom的UploadBean
jspSmartUpload 简单易用，但是它好像不是开源的，也不怎么更新了，它上传要把文件放入内存，不适合传大文件，
推荐使用commons-fileupload
开源组件，有更新，可以上传大文件。Struts也是采用它处理上传。
commons-fileupload下载地址：
http://commons.apache.org/fileupload/
下载：commons-fileupload-1.3-bin.zip 得到：commons-fileupload-1.3.jar
http://commons.apache.org/io/
下载：commons-io-2.2-bin.zip 得到：commons-io-2.2.jar
upload.jsp
<%@ page language="java" contentType="text/html; charset=UTF-8"%>
<html>
<head>
<title>using commons Upload to upload file</title>
</head>
<style>
* {
font-family: "宋体";
font-size: 14px
}
</style>
<body>
<p align="center">请您选择需要上传的文件</p>
<form id="form1" name="form1" method="post"
action="servlet/fileServlet" enctype="multipart/form-data">
<table border="0" align="center">
<tr>
<td>上传人：</td>
<td><input name="name" type="text" id="name" size="20"></td>
</tr>
<tr>
<td>上传文件：</td>
<td><input name="file" type="file" size="20"></td>
</tr>
<tr>
<td></td>
<td><input type="submit" name="submit" value="提交"> <input
type="reset" name="reset" value="重置"></td>
</tr>
</table>
</form>
</body>
</html>
FileUploadServlet.java
package com.urt.module.upload;
import java.io.File;
import java.io.IOException;
import java.util.*;
import javax.servlet.ServletConfig;
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;
/**
* 上传Servlet
* @author happyqing
* 2013.10.29
*/
public class FileUploadServlet extends HttpServlet {
private static final long serialVersionUID = -7744625344830285257L;
private ServletContext sc;
private String savePath;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void init(ServletConfig config) {
// 在web.xml中设置的一个初始化参数
savePath = config.getInitParameter("savePath");
sc = config.getServletContext();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("UTF-8");
DiskFileItemFactory factory = new DiskFileItemFactory();
ServletFileUpload upload = new ServletFileUpload(factory);
try {
List items = upload.parseRequest(request);
Iterator itr = items.iterator();
while (itr.hasNext()) {
FileItem item = (FileItem) itr.next();
if (item.isFormField()) {
System.out.println("表单参数名:" + item.getFieldName()
+ "，表单参数值:" + item.getString("UTF-8"));
} else {
if (item.getName() != null && !item.getName().equals("")) {
System.out.println("上传文件的大小:" + item.getSize());
System.out.println("上传文件的类型:" + item.getContentType());
// item.getName()返回上传文件在客户端的完整路径名称
System.out.println("上传文件的名称:" + item.getName());
File tempFile = new File(item.getName());
// 上传文件的保存路径 //运行目录下
File file = new File(sc.getRealPath("/") + savePath,
tempFile.getName());
item.write(file);
request.setAttribute("upload.message", "上传文件成功！");
} else {
request.setAttribute("upload.message", "没有选择上传文件！");
}
}
}
} catch (FileUploadException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
request.setAttribute("upload.message", "上传文件失败！");
}
request.getRequestDispatcher("/uploadResult.jsp").forward(request,
response);
}
}
uploadResult.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>uploadResult</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>
${requestScope['upload.message'] }
<a href="/upload/uploadFile.jsp">上传文件</a>
</body>
</html>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
id="WebApp_ID" version="2.5">
<display-name>redcrossModule</display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
<welcome-file>upload.jsp</welcome-file>
</welcome-file-list>
<servlet>
<description></description>
<display-name>FileUploadServlet</display-name>
<servlet-name>FileUploadServlet</servlet-name>
<servlet-class>com.urt.module.upload.FileUploadServlet</servlet-class>
<!--设置初始化参数 -->
<init-param>
<param-name>savePath</param-name>
<param-value>upload</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>FileUploadServlet</servlet-name>
<url-pattern>/servlet/fileServlet</url-pattern>
</servlet-mapping>
</web-app>
参考：
使用 common-fileupload 实现文件上传
Java 文件上传组件 Apache Commons FileUpload 应用指南
