code: public void setLongdesc(String longdesc) {
          _imageState.registerAttribute(AbstractHtmlState.ATTR_GENERAL, HtmlConstants.LONGDESC, longdesc);
      }
docs: Sets the longdesc attribute for the HTML image tag.
  
  @param longdesc the longdesc attribute
  @jsptagref.attributedescription The longdesc attribute for the HTML image tag.
  @jsptagref.attributesyntaxvalue <i>string_alt</i>
  @netui:attribute required="false" rtexprvalue="true"
  description="the longdesc for the HTML image tag."