Where is the downloaded file?

Question

I'm using the Upload component in a Vaadin8 project to get a file up on the server, as shown in the source code on this page:

https://demo.vaadin.com/sampler/#ui/data-input/other/upload

After I choose the file on my pc and click upload, the window opens up just like in the sampler, and the progress bar goes all the way to the end, but the file is nowhere to be found in the project file system. Is there another step I'm supposed to be doing? How to I configure the destination folder for the uploaded files?

Answer 1

Taken from official documentation here Receiving upload:

The uploaded files are typically stored as files in a file system, in a database, or as temporary objects in memory. The upload component writes the received data to an java.io.OutputStream so you have plenty of freedom in how you can process the upload content.

So in your case, an uploaded file is stored as a temporary object. In V8 documentation example is cut-off, but it's presented in V7: Receiving Upload Data

 public OutputStream receiveUpload(String filename,
                                      String mimeType) {
        // Create upload stream
        FileOutputStream fos = null; // Stream to write to
        try {
            // Open the file for writing.
            file = new File("/tmp/uploads/" + filename);
            fos = new FileOutputStream(file);
        } catch (final java.io.FileNotFoundException e) {
            new Notification("Could not open file<br/>",
                             e.getMessage(),
                             Notification.Type.ERROR_MESSAGE)
                .show(Page.getCurrent());
            return null;
        }
        return fos; // Return the output stream to write to
    }
 public void uploadSucceeded(SucceededEvent event) {
        // Show the uploaded file in the image viewer
        image.setVisible(true);
        image.setSource(new FileResource(file));
    }

So the idea is that you could create a file yourself, once upload has succeed.