StreamResource not calling getStream()

Vaadin 6 / 7 / 8
1

Hi,
I have a problem similar to this :https://vaadin.com/old-forum/#!/thread/2789663/2789662

I am trying to check out the sample code for StreamResource from the Book of Vaadin. However in my case the getStream() method is not invoked. Am I missing something ?

2

Code snippet are as follows.
The UI Class:

public class ImagesourceprojectUI extends UI {

    @WebServlet(value = "/*", asyncSupported = true)
    @VaadinServletConfiguration(productionMode = false, ui = ImagesourceprojectUI.class)
    public static class Servlet extends VaadinServlet {
    }

    @Override
    protected void init(VaadinRequest request) {
        final VerticalLayout layout = new VerticalLayout();
        layout.setMargin(true);
        setContent(layout);

        Button button = new Button("Click Me");
        button.addClickListener(new Button.ClickListener() {
            public void buttonClick(ClickEvent event) {
                layout.addComponent(new Label("Thank you for clicking"));
            }
        });
        layout.addComponent(button);
        
        StreamResource.StreamSource imagesource = new ImageSource();
        StreamResource resource =
                new StreamResource(imagesource, "myimage.png");
        layout.addComponent(new Image("Image title", resource));
    }

}

The Class implementing StreamSource

public class ImageSource implements StreamSource {

    ByteArrayOutputStream imagebuffer = null;
    int reloads = 0;
    @Override
    public InputStream getStream() {
        System.out.println("In getStream");
        // TODO Auto-generated method stub
        BufferedImage image = new BufferedImage (200, 200,
                BufferedImage.TYPE_INT_RGB);
                Graphics drawable = image.getGraphics();
                drawable.setColor(Color.lightGray);
                drawable.fillRect(0,0,200,200);
                drawable.setColor(Color.yellow);
                drawable.fillOval(25,25,150,150);
                drawable.setColor(Color.blue);
                drawable.drawRect(0,0,199,199);
                drawable.setColor(Color.black);
                drawable.drawString("Reloads="+reloads, 75, 100);
                reloads++;
                try {
                    /* Write the image to a buffer. */
                    imagebuffer = new ByteArrayOutputStream();
                    ImageIO.write(image, "png", imagebuffer);
                    /* Return a stream from the buffer. */
                    return new ByteArrayInputStream(
                            imagebuffer.toByteArray());
                    } catch (IOException e) {
                        return null;
                    }
    }

}