tomcat HttpServletRequest getParameter 偶尔不能获取到值，什么原因？

getQueryString 可以获取到的话,就自己取出queryString自己解析

Map<String, Object> params = new HashMap<String, Object>();
        if (StringUtils.isNotEmpty(queryString)) {
 
            Pattern ptn = Pattern.compile("([^=]+)=([^&]+)&?");
            Matcher mtc = ptn.matcher(queryString);
            while (mtc.find()) {
                String key = mtc.group(1);
                String value = mtc.group(2);
                try {
                    value = URLDecoder.decode(value, "UTF-8");
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                }
                params.put(key, value);
            }
        }