/* 上傳檔案至Server的方法 */
  private void uploadFile() {
    String end = "\r\n";
    String twoHyphens = "--";
    String boundary = "*****";
    String newName = "image.jpg";
    String uploadFile = "storage/sdcard1/bagPictures/102.jpg";
    ;
    String actionUrl = "http://192.168.1.123:8080/upload/servlet/UploadServlet"
 
;
    try {
      URL url = new URL(actionUrl);
      HttpURLConnection con = (HttpURLConnection) url.openConnection();
      /* 允許Input、Output，不使用Cache */
      con.setDoInput(true);
      con.setDoOutput(true);
      con.setUseCaches(false);
      /* 設定傳送的method=POST */
      con.setRequestMethod("POST"
 
);
      /* setRequestProperty */
      con.setRequestProperty("Connection", "Keep-Alive");
      con.setRequestProperty("Charset", "UTF-8");
      con.setRequestProperty("Content-Type",
          "multipart/form-data;boundary=" + boundary);
      /* 設定DataOutputStream */
      DataOutputStream ds = new DataOutputStream(con.getOutputStream());
      ds.writeBytes(twoHyphens + boundary + end);
      ds.writeBytes("Content-Disposition: form-data; "
 

          + "name=\"file1\";filename=\"" + newName + "\"" + end);
      ds.writeBytes(end);
      /* 取得檔案的FileInputStream */
      FileInputStream fStream = new FileInputStream(uploadFile);
      /* 設定每次寫入1024bytes */
      int bufferSize = 1024;
      byte[] buffer = new byte[bufferSize];
      int length = -1;
      /* 從檔案讀取資料至緩衝區 */
      while ((length = fStream.read(buffer)) != -1) {
        /* 將資料寫入DataOutputStream中 */
        ds.write(buffer, 0, length);
      }
      ds.writeBytes(end);
      ds.writeBytes(twoHyphens + boundary + twoHyphens + end);
      /* close streams */
      fStream.close();
      ds.flush();
      /* 取得Response內容 */
      InputStream is = con.getInputStream();
      int ch;
      StringBuffer b = new StringBuffer();
      while ((ch = is.read()) != -1) {
        b.append((char) ch);
      }
      /* 將Response顯示於Dialog */
      showDialog("上傳成功" + b.toString().trim());
      /* 關閉DataOutputStream */
      ds.close();
    } catch (Exception e) {
      showDialog("上傳失敗" + e);
    }
  }

伺服器端接收部分

public class UploadServlet extends HttpServlet {

  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    try {
      System.out.println("IP:" + request.getRemoteAddr());
      // 1、建立工廠類：DiskFileItemFactory
      DiskFileItemFactory facotry = new DiskFileItemFactory();
      String tempDir = getServletContext().getRealPath("/WEB-INF/temp");
      facotry.setRepository(new File(tempDir));//設定臨時檔案存放目錄
      // 2、建立核心解析類：ServletFileUpload
      ServletFileUpload upload = new ServletFileUpload(facotry);
      upload.setHeaderEncoding("UTF-8");// 解決上傳的檔名亂碼
      upload.setFileSizeMax(1024 * 1024 * 1024);// 單個檔案上傳最大值是1M
      upload.setSizeMax(2048 * 1024 * 1024);//檔案上傳的總大小限制

      // 3、判斷使用者的表單提交方式是不是multipart/form-data
      boolean bb = upload.isMultipartContent(request);
      if (!bb) {
        return;
      }
      // 4、是：解析request物件的正文內容List<FileItem>
      List<FileItem> items = upload.parseRequest(request);
      String storePath = getServletContext().getRealPath(
          "/WEB-INF/upload");// 上傳的檔案的存放目錄
      for (FileItem item : items) {
        if (item.isFormField()) {
          // 5、判斷是否是普通表單：列印看看
          String fieldName = item.getFieldName();// 請求引數名
          String fieldValue = item.getString("UTF-8");// 請求引數值
          System.out.println(fieldName + "=" + fieldValue);
        } else {
          // 6、上傳表單：得到輸入流，處理上傳：儲存到伺服器的某個目錄中，儲存時的檔名是啥？
          String fileName = item.getName();// 得到上傳檔案的名稱 C:\Documents
                            // and
                            // Settings\shc\桌面\a.txt
                            // a.txt
          //解決使用者沒有選擇檔案上傳的情況
          if(fileName==null||fileName.trim().equals("")){
            continue;
          }
          fileName = fileName
              .substring(fileName.lastIndexOf("\\") + 1);
          String newFileName = UUIDUtil.getUUID() + "_" + fileName;
          System.out.println("上傳的檔名是：" + fileName);
          InputStream in = item.getInputStream();
          String savePath = makeDir(storePath, fileName) + "\\"
              + newFileName;
          OutputStream out = new FileOutputStream(savePath);
          byte b[] = new byte[1024];
          int len = -1;
          while ((len = in.read(b)) != -1) {
            out.write(b, 0, len);
          }
          in.close();
          out.close();
          item.delete();//刪除臨時檔案
        }
      }
    }catch(FileUploadBase.FileSizeLimitExceededException e){
      request.setAttribute("message", "單個檔案大小不能超出5M");
      request.getRequestDispatcher("/message.jsp").forward(request,
          response);
    }catch(FileUploadBase.SizeLimitExceededException e){
      request.setAttribute("message", "總檔案大小不能超出7M");
      request.getRequestDispatcher("/message.jsp").forward(request,
          response);
  }catch (Exception e) {
      e.printStackTrace();
      request.setAttribute("message", "上傳失敗");
      request.getRequestDispatcher("/message.jsp").forward(request,
          response);
    }
  }

  // WEB-INF/upload/1/3 打散儲存目錄
  private String makeDir(String storePath, String fileName) {
    int hashCode = fileName.hashCode();// 得到檔名的hashcode碼
    int dir1 = hashCode & 0xf;// 取hashCode的低4位 0~15
    int dir2 = (hashCode & 0xf0) >> 4;// 取hashCode的高4位 0~15
    String path = storePath + "\\" + dir1 + "\\" + dir2;
    File file = new File(path);
    if (!file.exists())
      file.mkdirs();
    System.out.println("儲存路徑是"+path);
    return path;
  }

  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
    doGet(request, response);
  }

}