code: protected void doResponseHeaders(final HttpServletResponse response, final String mimeType) {
          if (mimeType != null) {
              response.setContentType(mimeType);
          }
      }
docs: Set the response headers. This method is called to set the response
  headers such as content type and content length. May be extended to add
  additional headers.
  
  @param response
  @param resource
  @param mimeType