Loading images to Ajaxswing web application

I would like to convert my desktop app to web app using Ajaxswing and as instructions say, I did all the same: http://ift.tt/2jCKj0a

The thing is that web app starts, but it doesn't load images. I put images to ajax images folder, but server still shows exception:

javax.imageio.IIOException: Can't read input file! at javax.imageio.ImageIO.read(ImageIO.java:1301)

Here is my code:

try {
                img = ImageIO.read(new File("resources/images/blackStone.png"));
                img = img.getScaledInstance(this.pixelSize, this.pixelSize, Image.SCALE_DEFAULT);
                icon = new ImageIcon(img);
                this.setOpaque(true);
                this.setContentAreaFilled(true);
                this.setIcon(icon);
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

Where img is Image,icon is ImageIcon and this is JButton. What should be path to blackStone.png. Any help would be appreciated :)