code: @Override
      public int doEndTag() throws JspException {
          SQLExecutionTag parent = (SQLExecutionTag)
  	    findAncestorWithClass(this, SQLExecutionTag.class);
  	if (parent == null) {
  	    throw new JspTagException(
                  Resources.getMessage("SQL_PARAM_OUTSIDE_PARENT"));
  	}
  
  	Object paramValue = null;
  	if (value != null) {
  	    paramValue = value;
          } else if (bodyContent != null) {
  	    paramValue = bodyContent.getString().trim();
  	    if (((String) paramValue).trim().length() == 0) {
  		paramValue = null;
  	    }
  	}
  
  	parent.addSQLParameter(paramValue);
  	return EVAL_PAGE;
      }
docs: Tag logic