code: private void writeHiddenParam(String paramName, String paramValue, AbstractRenderAppender results,
                                    ServletRequest req, boolean newLine)
      {
          // put each hidden on a new line
          if (newLine)
              results.append("\n");
  
          // create the state
          _hiddenState.clear();
          _hiddenState.name = paramName;
          _hiddenState.value = paramValue;
  
          TagRenderingBase hiddenTag = TagRenderingBase.Factory.getRendering(TagRenderingBase.INPUT_HIDDEN_TAG, req);
          hiddenTag.doStartTag(results, _hiddenState);
          hiddenTag.doEndTag(results);
      }
docs: Write a hidden field for a paramter
  @param paramName  The name of the parameter
  @param paramValue The value of the paramter
  @param results    The InternalStringBuilder to append the result to
  @param req        THe servlet request