<form action="xxx" method="post" enctype="multipart/form-data">

  用户名；<input type="text" name="username"/><br/>

  照　片：<input type="file" name="zhaoPian"/><br/>

  <input type="submit" value="上传"/>

</form>

public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        request.setCharacterEncoding("utf-8");

        response.setContentType("text/html;charset=utf-8");

        /*

         * 上传三步

         * 1. 得到工厂

         * 2. 通过工厂创建解析器

         * 3. 解析request，得到FileItem集合

         * 4. 遍历FileItem集合，调用其API完成文件的保存

         */

        DiskFileItemFactory factory = new DiskFileItemFactory();

        ServletFileUpload sfu = new ServletFileUpload(factory);

        try {

            List<FileItem> fileItemList = sfu.parseRequest(request);

            FileItem fi1 = fileItemList.get(0);

            FileItem fi2 = fileItemList.get(1);

            System.out.println("普通表单项演示：" + fi1.getFieldName() +

                    "=" + fi1.getString("UTF-8"));

            System.out.println("文件表单项演示：");

            System.out.println("Content-Type: " + fi2.getContentType());

            System.out.println("size: " + fi2.getSize());

            System.out.println("filename: " + fi2.getName());

            // 保存文件

            File destFile = new File("D:/baibing.jpg");

            fi2.write(destFile);

        } catch (FileUploadException e) {

            throw new RuntimeException(e);

        } catch (Exception e) {

            throw new RuntimeException(e);

        }

    }

  String filename = fi2.getName();

    int index = filename.lastIndexOf("\\");

    if(index != -1) {

        filename = filename.substring(index+1);

    }

public class Upload3Servlet extends HttpServlet {

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        DiskFileItemFactory factory = new DiskFileItemFactory();//获取工厂

        ServletFileUpload sfu = new ServletFileUpload(factory);//获取解析器

        try {

            List<FileItem> fileItemList = sfu.parseRequest(request);

            FileItem fi= fileItemList.get(1);

            String root=this.getServletContext().getRealPath("/WEB-INF/files/");

            /*得到文件名，生成哈希值,

             * 转换成16进制

             */

            //处理绝对路径

             String filename=fi.getName();

             int index = filename.lastIndexOf("\\");

             if(index != -1) {

                 filename = filename.substring(index+1);

                }

             //处理文件同名问题

             String savename= CommonUtils.uuid() + "_" +filename;

             //得到哈希值

             int hCode=filename.hashCode();

             String hex=Integer.toHexString(hCode);

             //截取前两位字母，与root链接生成完整路径

             File dirFile = new File(root,hex.charAt(0) + "/" +hex.charAt(1));

               //创建目录链

             dirFile.mkdirs();

             //创建目录

             File destFile = new File(dirFile, savename);

             //保存

             fi.write(destFile);

        }catch (Exception e) {

            throw new RuntimeException(e);

        }

    }

}