Java SWT Browser opens download dialog when viewing PDF on Linux

I have following code which works well on Windows:

private void showSelectedPdf() {
    File selected = getSelectedPdf();

    if(selected != null) {
        String path = selected.getAbsolutePath();
        browser.setUrl(path);
    }
}

But on Linux it only shows download dialog. It is very strange, because my default browser is Firefox and when i type

$ firefox blabla.pdf

it opens normal Firefox window with displayed PDF.

Is there any easy way to display PDF with SWT Browser on Windows and Linux?

Thanks in advance

Copyright Notice：Content Author:「Firzen」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/20220910/java-swt-browser-opens-download-dialog-when-viewing-pdf-on-linux