private void checkImageCache(final String aID, final String aLevel, final String aScale, final String aRegion,
final float aRotation, final HttpServletRequest aRequest, final HttpServletResponse aResponse)
throws IOException, ServletException {
final PairtreeRoot cacheDir = new PairtreeRoot(new File(myCache));
final PairtreeObject cacheObject = cacheDir.getObject(aID);
final String fileName = CacheUtils.getFileName(aLevel, aScale, aRegion, aRotation);
final File imageFile = new File(cacheObject, fileName);
if (imageFile.exists()) {
final ServletOutputStream outStream = aResponse.getOutputStream();