在Node JS服务器上接收来自Dart的POST请求时，JSON字符串的值为空

const express = require('express');
const bodyParser = require('body-parser');
const app = express();

app.use(bodyParser.json());

app.post('/api/endpoint', (req, res) => {
  const jsonData = req.body;
  // 处理jsonData
});

app.listen(3000, () => {
  console.log('Server started on port 3000');
});

import 'dart:convert';
import 'package:http/http.dart' as http;

void main() async {
  final url = 'http://your-node-server/api/endpoint';
  
  final data = {'key': 'value'};
  final headers = {'Content-Type': 'application/json'};
  
  final response = await http.post(
    Uri.parse(url),
    headers: headers,
    body: jsonEncode(data),
  );
  
  // 处理响应
}