在java里实现文件上传的组件好多，如jspSmartUpload、commons-fileupload，但是jspSmartUpload差不多淘汰了。在网上找了下 apache的commons-fileupload相关的使用，调通了程序，放在这里以后好直接使用。。用到的jar包：（到www.apache.org下载即可）commons-fileupload-1.2.1.jarcommons-io-1.4.jar网上还有更详细的用法：http://www.cnblogs.com/yyw84/archive/2007/06/27/797652.html由于代码太多，如果大家有兴趣，可以自己去参考参考。这是我自己机器上通过的简单的代码，放在下面：web.xml<?xml version="1.0" encoding="UTF-8"?><web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"><servlet><servlet-name>FileUpload</servlet-name><servlet-class>FileUpload.FileUploadServlet</servlet-class></servlet><servlet-mapping><servlet-name>FileUpload</servlet-name><url-pattern>/servlet/FileUploadServlet</url-pattern></servlet-mapping> <welcome-file-list><welcome-file>fileUpload.jsp</welcome-file></welcome-file-list></web-app>FileUpload.javapackage FileUpload;import java.io.File;import java.io.IOException;import java.io.PrintWriter;import java.util.Iterator;import java.util.List;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.FileUploadBase.SizeLimitExceededException;import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload;public class FileUploadServlet extends HttpServlet {public FileUploadServlet() { super();}public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { final String appRealPath = this.getServletContext().getRealPath("/"); //获取web app的物理路径 final long MAX_SIZE = 3 * 1024 * 1024;// 设置上传文件最大为 3M final String[] allowedExt = new String[] { "jpg", "jpeg", "gif", "txt","doc", "docx", "mp3", "wma", "m4a" }; // 允许上传的文件格式的列表 response.setContentType("text/html"); response.setCharacterEncoding("UTF-8"); // 设置字符编码为UTF-8, 这样支持汉字显示 // 实例化一个硬盘文件工厂,用来配置上传组件ServletFileUpload DiskFileItemFactory dfif = new DiskFileItemFactory(); dfif.setSizeThreshold(4096);// 设置上传文件时用于临时存放文件的内存大小,这里是4K.多于的部分将临时存在硬盘 dfif.setRepository(new File(appRealPath + "ImagesUploadTemp\\")); // 设置存放临时文件的目录,web根目录下的ImagesUploadTemp目录 // 用以上工厂实例化上传组件 ServletFileUpload sfu = new ServletFileUpload(dfif); sfu.setSizeMax(MAX_SIZE);// 设置最大上传尺寸 PrintWriter out = response.getWriter(); // 从request得到 所有 上传域的列表 List fileList = null; try {fileList = sfu.parseRequest(request); } catch (FileUploadException e) {// 处理文件尺寸过大异常if (e instanceof SizeLimitExceededException) { out.println("文件尺寸超过规定大小:" + MAX_SIZE + "字节<p />"); out.println("<a href=\" " + request.getContextPath() + "/fileUpload.jsp" + " \" target=\"_top\">返回</a>"); return;}e.printStackTrace(); } // 没有文件上传 if (fileList == null || fileList.size() == 0) {out.println("请选择上传文件<p />");out.println("<a href=\" " + request.getContextPath() + "/fileUpload.jsp" + " \" target=\"_top\">返回</a>");return; } // 得到所有上传的文件 Iterator fileItr = fileList.iterator(); // 循环处理所有文件 while (fileItr.hasNext()) {FileItem fileItem = null;String path = null;long size = 0;// 得到当前文件fileItem = (FileItem) fileItr.next();// 忽略简单form字段而不是上传域的文件域(<input type="text" />等)if (fileItem == null || fileItem.isFormField()) { continue;}// 得到文件的完整路径path = fileItem.getName();// 得到文件的大小size = fileItem.getSize();if ("".equals(path) || size == 0) { out.println("请选择上传文件<p />"); out.println("<a href=\" " + request.getContextPath() + "/fileUpload.jsp" + " \" target=\"_top\">返回</a>"); return;}// 得到去除路径的文件名String t_name = path.substring(path.lastIndexOf("\\") + 1);// 得到文件的扩展名(无扩展名时将得到全名)String t_ext = t_name.substring(t_name.lastIndexOf(".") + 1);// 拒绝接受规定文件格式之外的文件类型int allowFlag = 0;int allowedExtCount = allowedExt.length;for (; allowFlag < allowedExtCount; allowFlag++) { if (allowedExt[allowFlag].equals(t_ext))break;}if (allowFlag == allowedExtCount) { out.println("请上传以下类型的文件<p />"); for (allowFlag = 0; allowFlag < allowedExtCount; allowFlag++)out.println("*." + allowedExt[allowFlag]+ " "); out .println("<a href=\" " + request.getContextPath() + "/fileUpload.jsp" + " \" target=\"_top\">返回</a>"); return;}long now = System.currentTimeMillis();// 根据系统时间生成上传后保存的文件名String prefix = String.valueOf(now);// 保存的最终文件完整路径,保存在web根目录下的ImagesUploaded目录下String u_name = appRealPath + "ImagesUploaded\\"+ prefix + "." + t_ext;try { // 保存文件 fileItem.write(new File(u_name)); out.println("文件上传成功. 已保存为: " + prefix + "." + t_ext + " 文件大小: " + size + "字节<p />"); out.println("<a href=\" " + request.getContextPath() + "/fileUpload.jsp" + " \" target=\"_top\">继续上传</a>");} catch (Exception e) { e.printStackTrace();} }}public void init() throws ServletException { // Put your code here}}fileUpload.jsp<%@ page language="java" import="java.util.*" pageEncoding="GB18030"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head> <title>My JSP 'fileUpload.jsp' starting page</title></head><body><form action="<%= request.getContextPath() %>/servlet/FileUploadServlet" method="post" enctype="multipart/form-data" ><input type="file" name="fileUpload" /><input type="submit" value="upload" /></form></body></html>记得在上传的form里指明enctype="multipart/form-data"，具体的读一下FileUpload.java就清楚了。
相关资源：commons-fileupload-1.2.1.jar