使用mongodb中已有的字段作为objectId来创建带有节点和express的REST api？

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => console.log('MongoDB Connected'))
  .catch(err => console.log(err));

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const mySchema = new Schema({
  objectId: {
    type: String,
    required: true
  },
  // 其他字段...
});

const MyModel = mongoose.model('MyModel', mySchema);

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

app.use(express.json());

// 定义路由
app.get('/api/mydata', (req, res) => {
  MyModel.find()
    .then(data => res.json(data))
    .catch(err => res.status(500).json({ error: err.message }));
});

// 其他路由...

// 启动服务器
const port = 3000;
app.listen(port, () => console.log(`Server started on port ${port}`));