code: protected MediaType getDefaultContentType(T t) throws IOException {
  		List<MediaType> mediaTypes = getSupportedMediaTypes();
  		return (!mediaTypes.isEmpty() ? mediaTypes.get(0) : null);
  	}
docs: Returns the default content type for the given type. Called when {@link #write}
  is invoked without a specified content type parameter.
  <p>By default, this returns the first element of the
  {@link #setSupportedMediaTypes(List) supportedMediaTypes} property, if any.
  Can be overridden in subclasses.
  @param t the type to return the content type for
  @return the content type, or {@code null} if not known