docs: public static String generateChooseWXPayJson(String prepay_id,String appId,String key){
  		String json = PayUtil.generateMchPayJsRequestJson(prepay_id, appId, key);
  		json = json.replaceAll("\"timeStamp\"","\"timestamp\"")
  				   .replaceAll(",?\"appId\":\"[^\"]*\",?","");
  		return json;
  	}