code: protected void filter(String value, AbstractRenderAppender writer, boolean markupHTMLSpaceReturn)
      {
          if (value.equals(" ")) {
              writer.append("&nbsp;");
              return;
          }
  
          HtmlUtils.filter(value, writer, markupHTMLSpaceReturn);
      }
docs: Filter the specified string for characters that are senstive to
  HTML interpreters, returning the string with these characters replaced
  by the corresponding character entities.
  @param value                 The string to be filtered and returned
  @param markupHTMLSpaceReturn convert space characters and return characters
  to &amp;nbsp; and &lt;br /&gt; marketup for html.