multipartFile转file修改文件名，再转回multipartFile

//临时文件地址
String[] filename = multipartFile.getOriginalFilename().split("\.");
String folderPath = System.getProperty("java.io.tmpdir") + File.separator + "ottc-ilp" + File.separator;
File folder = new File(folderPath);
folder.mkdirs();
String path = folderPath + File.separator + filename[0] + System.currentTimeMillis() + "." + filename[1];
File file = new File(path);
//转成file
FileUtils.copyInputStreamToFile(multipartFile.getInputStream(), file);
FileInputStream fileInputStream = new FileInputStream(file);
//转回multipartFile
MockMultipartFile file1 = new MockMultipartFile("file", file.getName(), null, fileInputStream);