code: public void addApp(String serviceId, String address) {
          if (hasGroup()) {
              JSONObject map = JSON.parseObject(this.fields.get(TracingConstants.APP_MAP));
              if (map.containsKey(serviceId)) {
                  return;
              }
              map.put(serviceId, address);
              this.fields.put(TracingConstants.APP_MAP, JSON.toJSONString(map));
              return;
          }
          raiseNonGroupException();
      }
docs: 添加App
  
  @param serviceId serviceId
  @param address   address