Use InputStream multiple times

Question

I have a view, from which the user can first generate a PDF depending on some parameters, and then download and/or send it via mail.

Now, the method for generating the PDF file returns an InputStream, which I then store as field of the class, like this:

public class PDFWindow extends VerticalLayout { ... private InputStream pdfInputStream; ... private void createPDF() { this.pdfInputStream = pdfCreator.createPDF(); }

My problem is, that the pdfInputStream is closed after it is consumed by the FileDownloader:

Button download = new Button("Download"); final FileDownloader fileDownloader = new FileDownloader( new StreamResource(() -> this.pdfInputStream, this.pdfFileName)); fileDownloader.extend(download);

or the SpringEmailService I wrote:

SpringEmailService.send( "[email protected]", recipients, this.subject.getValue(), this.message.getValue(),this.pdfInputStream,"test.pdf", "application/pdf");

Is there any way, to stop the InputStream from being closed and then closing it manual, or should I look for a completely different way?

Just don't store an InputStream as a field. Ask the creator to create the stream every time you need one. If it's too expensive, then store the generated bytes in memory, or in a file, or in your database, or wherever you want. — JB Nizet
– JB Nizet, Commented Jul 6, 2018 at 8:51
Thanks a lot! I changed it so, that I store the byte Array as a field instead, and it works perfectly. Could you post an answer, so that I can accept it? — Niby
– Niby, Commented Jul 6, 2018 at 9:11

JB Nizet · Accepted Answer · 2018-07-06 09:12:51Z

Just don't store an InputStream as a field.

Ask the creator to create the stream every time you need one.

If it's too expensive, then store the generated bytes in memory, or in a file, or in your database, or wherever you want, and create a stream over these bytes/file whenever you need one.

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