code: protected void doTag(Writer out) throws JspException, IOException {
  		JspFragment body = getJspBody();
  		if(body!=null) {
  			// Check for JspWriter to avoid a JspWriter wrapping a JspWriter
  			body.invoke(
  				(out instanceof JspWriter)
  				? null
  				: out
  			);
  		}
  	}
docs: Once the out JspWriter has been replaced to output the proper content
  type, this version of invoke is called.
  
  @param  out  the output.  If passed-through, this will be a <code>JspWriter</code>
  
  @implSpec This default implementation invokes the jsp body, if present.
  
  @throws javax.servlet.jsp.JspTagException