code: public File write(File destination) throws IOException {
  		assertValid();
  		
  		if (destination.isDirectory() == true) {
  			destination = new File(destination, this.header.getFileName());
  		}
  		if (data != null) {
  			FileUtil.writeBytes(data, destination);
  			data = null;
  		} else {
  			if (tempFile != null) {
  				FileUtil.move(tempFile, destination, true);
  			}
  		}
  		return destination;
  	}
docs: 将上传的文件写入目标文件<br>
  写入后原临时文件会被删除
  
  @return 目标文件