如何解决在express js中无法读取未定义的属性'name‘？

const express = require('express');
const app = express();

// 解析 application/json
app.use(express.json());

// 解析 application/x-www-form-urlencoded
app.use(express.urlencoded({ extended: true }));

app.post('/example', (req, res) => {
    console.log(req.body.name); // 现在这应该可以工作了
    res.send('Data received');
});

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

app.post('/example', (req, res) => {
    const name = req.body?.name || 'Default Name';
    console.log(name);
    res.send(`Name is: ${name}`);
});

app.use((err, req, res, next) => {
    console.error(err.stack);
    res.status(500).send('Something broke!');
});

const { body, validationResult } = require('express-validator');

app.post('/example', [
    body('name').isString().notEmpty()
], (req, res) => {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
        return res.status(400).json({ errors: errors.array() });
    }
    console.log(req.body.name);
    res.send('Data received');
});