code: public Object evaluate(TaskRequest req, TaskResponse res) {
  		
  		HttpServletRequest hreq = (HttpServletRequest) source.evaluate(req, res);
  		String parameterName = (String) parameter_name.evaluate(req, res);
  		
  		return hreq.getSession().getServletContext().getInitParameter(parameterName);
  	}
docs: {@inheritDoc}