React-获取请求不在正文中发送内容

我没有从body对象中获取数据 fetch 在我的服务器端请求。我已经尝试了其他的解决方法,但到目前为止,我的情况还没有任何效果。我在后端使用Node express,在前端使用React。

组件中:

addCity = _ => {
    const { city } = this.state;
    fetch('http://localhost:3003/city_create', {
      method: "POST",
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        create_name: city.name,
        create_district: city.district,
        create_population: city.population
      })
    })
      .then(res => {
        console.log(res);
        this.getCities;
      })
      .catch(err => console.log(err))

  }

服务器路由:

router.post('/city_create', (req, res) => {
    console.log("Trying to create new city...")
    const { create_name, create_district, create_population } = req.body;
    //debugger
    const queryString = "INSERT INTO city (Name, District, Population, CountryCode) VALUES (?,?,?,'PAK')";

    getConnection().query(queryString, [create_name, create_district, create_population], (err, rows, fields) => {
        console.log(create_name, create_district, create_population);
        if (err) {
            console.log('A db error occurred:' + err);
            res.sendStatus(500);
            return;
            //throw err;
        }
        console.log("Inserted a new City with Id: ", rows.insertId);
    });

    res.end();
});

尝试使用 FormData accept 标题中也有属性,但没有运气。