How to add attachments to email in Java using OutputStream?

I've seen the code for javax.mail library where you add attachments to the email doing this:

MimeBodyPart attachmentPart = new MimeBodyPart();
FileDataSource fds = new FileDataSource("C:/text.txt");
attachmentPart.setDataHandler(new DataHandler(fds));
attachmentPart.setFileName("text.txt");
multipart.addBodyPart(attachmentPart);

But this requires that the file reside somewhere on this disk.

I would like to grab an OutputStream right from the email library and stream file contents into it directly from another place where I write to that OutputStream.

Is this possible?