I have an application that provides a feature to export part of the scene as an image. I'm using FileSaveService to do that..something like that:


        exportWorkflowButton.setOnAction(new EventHandler<ActionEvent>() {
            public void handle(ActionEvent event) {
                try {
                    if(fileSaveService == null)//lazy init
                        fileSaveService = (FileSaveService) ServiceManager.lookup("javax.jnlp.FileSaveService");

                    
                    Object renderToImage = canvas.renderToImage(null, 1.5f);
                    Image sceneImage = Image.impl_fromPlatformImage(renderToImage);
                    
                    ByteArrayOutputStream os = new ByteArrayOutputStream();
                    ImageIO.write(ImageConverter.convertToAwtImage(sceneImage), "png", os);
                    InputStream imageInputStream = new ByteArrayInputStream(os.toByteArray());
                    
                    //Save the image using the JNLP FileSaveService
                    fileSaveService.saveFileDialog(null, supportedImageExportExtensions, imageInputStream, workSession.getWorkflow().getId()+".png");
                    
                    
                } catch(Exception e) { //Can't locate JNLP service or can't write to filesystem
                    logger.warning("Can't export canvas to image, due to: " + formatStackTrace(e));
                    DialogManager.showErrorDialog(ImperiaResourceBundle.getBundle().getString("gui.error.exportToImage"));
                }
            }
        });


When the user clicks on the Export button: there's a File Chooser Dialog(swing-based ?!)... then the user needs to input a filename.
If the user selects an existing file and clicks 'Save' the applet crashes. Otherwise if there's no an existing file the image is saved correctly