code: protected void doHandleTargetedRequest(final Request request) {
  
  		// Check for file id
  		String fileId = request.getParameter(FILE_UPLOAD_ID_KEY);
  		if (fileId == null) {
  			throw new SystemException("No file id provided for content request.");
  		}
  
  		// Check valid file id
  		FileWidgetUpload file = getFile(fileId);
  		if (file == null) {
  			throw new SystemException("Invalid file id [" + fileId + "].");
  		}
  
  		// Check if thumb nail requested
  		boolean thumbNail = request.getParameter(FILE_UPLOAD_THUMB_NAIL_KEY) != null;
  		if (thumbNail) {
  			doHandleThumbnailRequest(file);
  		} else {
  			doHandleFileContentRequest(file);
  		}
  	}
docs: Handle a targeted request. Can be a file upload, thumbnail request or file content request.
  
  
  @param request the request being processed