Vaadin上传不适用于相同的文件名

Question

我正在尝试使用Vaadin上传上传.xlsx文件，当我再次上传同一个文件时，没有任何事情发生，它也不会触发任何事件。我第一次可以上传文件，它工作得很好，但在那之后，当我尝试再次上传同一个文件时，没有任何反应。我无法弄清楚这个问题。

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();
    }

}