最近在帮同学做大作业，用到了文件上传，在网上搜了一下，看到了高手写的很好的代码，学习了....
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 long MAX_SIZE = 3 * 1024 * 1024;// 设置上传文件最大为 3M // 允许上传的文件格式的列表 final String[] allowedExt = new String[] { "jpg", "jpeg", "gif", "txt", "doc", "docx", "mp3", "wma", "m4a" }; response.setContentType("text/html"); // 设置字符编码为UTF-8, 这样支持汉字显示 response.setCharacterEncoding("UTF-8"); // 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(request.getRealPath("/") + "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); // 设置最大上传尺寸 sfu.setSizeMax(MAX_SIZE); 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=\"upload.html\" 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=\"upload.html\" 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=\"upload.html\" 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("<p /><a href=\"upload.html\" 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 = request.getRealPath("/") + "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=\"upload.html\" target=\"_top\">继续上传</a>"); } catch (Exception e) { e.printStackTrace(); } } } public void init() throws ServletException { // Put your code here }}
至于其他的代码，我想大家应该都会，就不在这卖弄了。 :wink:
相关资源：servlet实现文件上传下载
