code: @Override
      public void refresh() {
          String url = mockupTypes.getUrl(mockupType);
          
          if (mockupId == null || url == null) {
              iframe.setSrc(null);
              return;
          }
          
          iframe.setSrc(String.format(url, mockupId, System.currentTimeMillis()));
      }
docs: Refreshes the iframe content.