get method in Express-mongodb“传入的参数必须是12个字节的单个字符串或24个十六进制字符的字符串”

const express = require('express');
const app = express();
const mongodb = require('mongodb');
const MongoClient = mongodb.MongoClient;

// 连接数据库
const url = 'mongodb://localhost:27017';
const dbName = 'mydb';

app.get('/users/:id', (req, res) => {
  const id = req.params.id;

  // 检查参数是否符合要求
  if (id.length !== 12 && id.length !== 24) {
    return res.status(400).json({ error: 'Invalid parameter' });
  }

  // 连接数据库并查询数据
  MongoClient.connect(url, (err, client) => {
    if (err) {
      return res.status(500).json({ error: 'Database connection error' });
    }

    const db = client.db(dbName);
    const collection = db.collection('users');

    collection.findOne({ _id: new mongodb.ObjectID(id) }, (err, result) => {
      if (err) {
        return res.status(500).json({ error: 'Database query error' });
      }

      if (!result) {
        return res.status(404).json({ error: 'User not found' });
      }

      res.json(result);
    });
  });
});

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