使用struts2实现一个文件上传功能并显示进度条

@Override public void parse(HttpServletRequest request, String saveDir)   throws IOException {  setLocale(request);　　　 　//规定了File文件的格式（如文件名必须是xxFileName，文件类型xxContentType），并定义了File的保存路径　　　　             DiskFileItemFactory factory = new DiskFileItemFactory();   ServletFileUpload upload = new ServletFileUpload(factory);//处理文件上传的servlet  upload.setProgressListener(new FileUploadProgressListener(request)); //为文件上传添加监听  factory.setSizeThreshold(0); //if (saveDir != null   factory.setRepository(new File(saveDir));//临时路径  }  try {   upload.setSizeMax(maxSize);   List items = upload.parseRequest(createRequestContext(request)); //获取所有请求   for (Object obItem : items) {    FileItem item = (FileItem) obItem; //获取每个请求的文件    if (LOG.isDebugEnabled()) {     LOG.debug("Found item" + item.getFieldName());    }    if (item.isFormField()) { //普通表单提交     LOG.debug("Item is a normal form field");     List<String> values;     if (params.get(item.getFieldName()) != null) {      values = params.get(item.getFieldName());     } else {      values = new ArrayList<String>();     }     String charset = request.getCharacterEncoding();     if (charset != null) {      values.add(item.getString(charset));     } else {      values.add(item.getString());     }     params.put(item.getFieldName(), values);    } else { //文件上传请求     LOG.debug("Item is a file upload");     if (item.getName() == null       || item.getName().trim().length() <= 0) {      LOG.debug("No file has been uploded for the filed:"        + item.getFieldName());      continue;     }     List<FileItem> values;     if (files.get(item.getFieldName()) != null) {      values = files.get(item.getFieldName());     } else {      values = new ArrayList<FileItem>();     }     values.add(item);     files.put(item.getFieldName(), values);    }   }  } catch (FileUploadBase.SizeLimitExceededException e) {   System.out.println("错误1：" + e);   if (LOG.isWarnEnabled()) {    LOG.warn("Request exceeded size limit!", e);   }   String errorMessage = buildErrorMessage(e, new Object[]{e.getPermittedSize(), e.getActualSize()});   if (!errors.contains(errorMessage)) {    errors.add(errorMessage);   }  } catch (Exception e) {   System.out.println("错误1：" + e);   if (LOG.isWarnEnabled()) {    LOG.warn("Unable to parse request", e);   }   String errorMessage = buildErrorMessage(e, new Object[]{});   if (!errors.contains(errorMessage)) {    errors.add(errorMessage);   }  } }