Vaadin upload not working for same filename

Question

I am trying to upload.xlsx file using Vaadin Upload, When I am upload the same file again nothing is happening, it does not fire any events too. For first time I can upload file, and it works very fine, but after that when I am trying to upload the same file again, nothing happens. I could not figure out the issue.

uploader = new Upload(null, this);
uploader.setImmediate(true);
uploader.setButtonCaption("Upload Template");

uploader.addStartedListener(this);
uploader.addFinishedListener(this);

@Override
public OutputStream receiveUpload(String filename, String mimeType) {
    uploadedFilename = filename;
    FileOutputStream fos = null; // Stream to write to
    try {

        String filepath = attachmentsTmpFolderLoc + File.separator + "Uploads";
        File folder = new File(filepath);
        if (!folder.exists()) {
            folder.mkdirs();
        }
        uploadFile = new File(filepath + File.separatorChar + filename);
        fos = new FileOutputStream(uploadFile);

    } catch (Exception e) {
        e.printStackTrace();
        return new NullOutputStream();
    }
    return fos;
}

@Override
public void uploadStarted(StartedEvent event) {
    uploader.setVisible(false);
}

@Override
public void uploadFinished(FinishedEvent event) {
    uploader.setVisible(true);
    getFinishedFile();


}

private void getFinishedFile() {
    String loginUserId = activeUserObject.getLoginId();
    String fileName = loginUserId + "_" + this.jobPkey + ".xlsx";

    if (!validatFileName(loginUserId, this.jobPkey)) {
        new IMCNotification().showError("Adressing - Wrong Template Name", "Please Upload file with Name : '" + fileName + "'.<BR> The uploaded file name should be the same as the downloaded file name.<BR> Please correct the file name and try again.");
        uploader.interruptUpload();

    } else {
        prepareCustomValidations();
    }

}

Answer 1

This is happening because value of target input is not getting changed, hence not firing the change event. Its a bug seen in Chrome/Chromium.

There is a fix in Vaadin 8.3 and newer versions to overcome this problem (see https://github.com/vaadin/framework/issues/9635 ).

If you are using older version of the framework, use below function to manually reset the target HTML file input field:

private void manuallyResetFileInput(String name) {
    final String js = String.format("for (let x of document.getElementsByName('%s')) if (x.type == 'file') x.value = '';", name);
    if (getUI() != null && getUI().getSession() != null) {
        getUI().access(() -> {
            Page.getCurrent().getJavaScript().execute(js);
        });
    } else {
        Page.getCurrent().getJavaScript().execute(js);
    }
}

You may have to add import com.vaadin.server.Page; to your imports.

Now call this function by passing name property of HTML file input field which you want to reset. You can find this via Inspect Element tool.