如何将字符串、字节数组转为输入流

String str = "budaye";
ByteArrayInputStream in = new ByteArrayInputStream(str.getBytes("UTF-8"));

InputStream inputStream = fileClient.downloadFile(tenantId, HivpBaseConstants.FileUpload.BUCKET_NAME_CAN, l.getUrl());
                                byte[] imgByte = StreamUtils.copyToByteArray(inputStream);

  public static byte[] readInputStream(InputStream is) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int length = 0;
        try {
            while ((length = is.read(buffer)) != -1) {
                baos.write(buffer, 0, length);
            }
            baos.flush();
        } catch (IOException e) {
            logger.error("IOException", e);
        }
        byte[] data = baos.toByteArray();
        try {
            is.close();
            baos.close();
        } catch (IOException e) {
            logger.error("IOException", e);
        }
        return data;
    }

imageFile = Base64Utils.encodeToString(data);

  //数据流转MultipartFile文件
                                MultipartFile multipartFile = new MockMultipartFile("file", "file" +"."+ fileType, fileType, inputStream);
                                ResponseEntity<ResponseCommonDTO> recognizeResult = hcanRemoteService.originalCheck(tenantId, companyCode, employeeNumber, multipartFile);

String path = "C:\\Users\\mai\\Desktop\\发票测试集合\\aaaaaaaaaa.pdf";
File file = new File(path);
InputStream ins = new FileInputStream(file);