spring - Create a Java File object (or equivalent) using a byte array in memory (without a physical file)

Question

I want to create a Java File object in memory (without creating a physical file) and populate its content with a byte array.

Can this be done?

The idea is to pass it to a Spring InputStreamSource. I'm trying the method below, but it returns saying "the byte array does not contain a file name.".

MimeMessage message = mailSender.createMimeMessage();
MimeMessageHelper helper = new MimeMessageHelper(message);      
helper.setFrom("no-reply@example.com", "xyz");
helper.setTo(email);
helper.setText(body,true);
helper.setSubject(subject);
helper.addInline("cImage",
        new InputStreamResource(new ByteArrayInputStream(imageByteArr)));

mailSender.send(message);

Answer 1

Can you paste the full stack trace? There is no such thing as an "in memory" file. Using a ByteArrayInputStream should be sufficient.

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You need to implement Resource#getFilename(). Try the following:

helper.addInline("cImage", new ByteArrayResource(imageByteArr){
            @Override
            public String getFilename() {
                return fileName;
            }
        });