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