code: public int doStartTag() throws JspException
      {
          // we assume that tagId will over have override id if both are defined.
          if (_state.id != null) {
              _idScript = renderNameAndId((HttpServletRequest) pageContext.getRequest(), _state, null);
          }
  
          // render the header...
          _writer = new WriteRenderAppender(pageContext);
          _br = TagRenderingBase.Factory.getRendering(TagRenderingBase.BODY_TAG, pageContext.getRequest());
          _br.doStartTag(_writer, _state);
  
          return EVAL_BODY_INCLUDE;
      }
docs: Process the start of the Button.
  @throws javax.servlet.jsp.JspException if a JSP exception has occurred