private MainError checkUploadFile(RopRequestContext rrctx) {
        ServiceMethodHandler serviceMethodHandler = rrctx.getServiceMethodHandler();
        if (serviceMethodHandler != null && serviceMethodHandler.hasUploadFiles()) {
            List<String> fileFieldNames = serviceMethodHandler.getUploadFileFieldNames();
            for (String fileFieldName : fileFieldNames) {
                String paramValue = rrctx.getParamValue(fileFieldName);
                if (paramValue != null) {
                    if (paramValue.indexOf("@") < 0) {
                        return MainErrors.getError(MainErrorType.UPLOAD_FAIL, rrctx.getLocale());
                    } else {
                        String fileType = UploadFileUtils.getFileType(paramValue);
                        if (!fileUploadController.isAllowFileType(fileType)) {//不支持的文件类型
                            return MainErrors.getError(MainErrorType.UPLOAD_FAIL, rrctx.getLocale());
                        }
                        byte[] fileContent = UploadFileUtils.decode(paramValue);
                        if (fileUploadController.isExceedMaxSize(fileContent.length)) {//大小超出限制
                            return MainErrors.getError(MainErrorType.UPLOAD_FAIL, rrctx.getLocale());
                        }
                    }
                }
            }
        }
        return null;
    }