code: public MediaType getContentType() {
  		String value = getFirst(CONTENT_TYPE);
  		return (StringUtils.hasLength(value) ? MediaType.parseMediaType(value) : null);
  	}
docs: Return the {@linkplain MediaType media type} of the body, as specified
  by the {@code Content-Type} header.
  <p>Returns {@code null} when the content-type is unknown.