code: public static void addError(final HttpServletRequest request, final String message) {
  		StringBuilder sb = (StringBuilder) request.getAttribute(ERROR_KEY);
  		if (sb == null) {
  			sb = new StringBuilder();
  			request.setAttribute(ERROR_KEY, sb);
  		}
  		sb.append(message);
  	}
docs: 附加错误内容。
  
  @param request
  请求
  @param message
  错误内容