code: public int doStartTag() throws JspException {
          oldParameters = new HashMap<String, Object>();
          parameterNames = new ArrayList<String>();
  
          return EVAL_BODY_INCLUDE;
      }
docs: This is the method called when the JSP interpreter first hits the tag
  associated with this class.  This method will firstly determine whether
  the page referenced by the {@code page} attribute exists.  If the
  page doesn't exist, this method will throw a {@code JspException}.
  If the page does exist, this method will hand control over to that JSP
  page.
  
  @exception JspException