Found a similar issue not long ago. There is a class that does just what you
mentioned, appends a timestamp as a request parameter of the <img> tag's
url. I think the class was NonCachingImage.
Cheers,
Xavier
2010/3/19 Doug Leeper <douglee...@yahoo.com>
> I am trying to create a barcode image from a user entered value. The image
> is to be updated while the user types. Hence I am using Ajax (onChange
> event) on the text field to regenerate the image. However, the image is not
> getting refreshed. It appears that the browser is not recognizing that the
> image has been updated. Is there a way to append a "timestamp" on the image
> url just for this image?
>
> or should I use a different type of resource?
>
> Note: the value entered has not be persisted so I don't believe I can a
> ResourceReference. Please correct me if I am wrong.
>
>
> Thanks
> - Doug
>
>
>
> BTW...Here is my code that I am using to generate the bar code:
>
> barCodeValueContainer = new WebMarkupContainer("barCodeValueContainer") {
> @Override
> public void onBeforeRender() {
> if (coupon.getObject().getBarCodeType() == null) {
> codeContainer.replace(new
> WebMarkupContainer("barCode"));
> } else if (barCodeErrorMessage == null) {
> codeContainer.replace(new BarCodeFragment("barCode",
> this));
> } else {
> codeContainer.replace(new ErrorFragment("barCode", this,
> barCodeErrorMessage));
> }
> super.onBeforeRender();
> }
>
> public boolean isVisible() {
> return coupon.getObject().getBarCodeType() != null;
> }
> };
>
> private class BarCodeFragment extends Fragment {
> public BarCodeFragment(String id, MarkupContainer markupProvider) {
> super(id, "barCodeFragment", markupProvider);
> setRenderBodyOnly(true);
>
> // Create the barcode bean
>
> String barCodeType = coupon.getObject().getBarCodeType();
> String barCodeValue = coupon.getObject().getBarCodeValue();
>
> AbstractBarcodeBean bean = null;
>
> if (barCodeType.equals(BarCodeType.CODE_39.id())) {
> bean = new Code39Bean();
> // bar width exactly one pixel
> ((Code39Bean) bean).setWideFactor(3);
> } else if (barCodeType.equals(BarCodeType.CODE_128.id())) {
> bean = new Code128Bean();
> } else if (barCodeType.equals(BarCodeType.UPC_A.id())) {
> bean = new UPCABean();
> }
>
> if (bean == null || barCodeValue == null) {
> add(new ErrorFragment("barCode", CouponDetailEditPanel.this,
> "Bar code value not set"));
> } else {
> final int dpi = 150;
>
> // Configure the barcode generator
> bean.setModuleWidth(UnitConv.in2mm(1.0f / dpi)); // makes
> the
> // narrow
>
> bean.doQuietZone(false);
>
> // Open output file
> ByteArrayOutputStream out = new ByteArrayOutputStream();
>
> try {
> // Set up the canvas provider for monochrome PNG output
> BitmapCanvasProvider canvas = new
> BitmapCanvasProvider(out,
> "image/png", dpi,
> BufferedImage.TYPE_BYTE_BINARY,
> false, 0);
>
> // Generate the barcode
> bean.generateBarcode(canvas, barCodeValue);
>
> System.out.println("VALUE: " + barCodeValue);
>
> // Signal end of generation
> canvas.finish();
> out.close();
> final byte[] content = out.toByteArray();
> Image img = new Image("barCode", new
> BarCodeImageResource(
> content));
> add(img);
> } catch (Exception e) {
> add(new ErrorFragment("barCode",
> CouponDetailEditPanel.this, e.getMessage()));
> }
> }
>
> }
> }
>
>
> private class BarCodeImageResource extends DynamicImageResource {
> private byte[] content;
>
> public BarCodeImageResource(byte[] content) {
> super("image/png");
> this.content = content;
> this.setLastModifiedTime(Time.now());
> }
>
> @Override
> protected byte[] getImageData() {
> return content;
> }
>
> }
>
