（节点：16448）UnhandledPromiseRejectionWarning：MongoExpiredSessionError：无法使用已结束的会话

Question

我尝试从 Node 连接到 MongoDB，但出现此错误：

（使用node --trace-warnings ... 显示警告的创建位置） （节点：16448）UnhandledPromiseRejectionWarning：未处理的承诺拒绝。此错误源于在没有 catch 块的情况下抛出异步函数内部，或拒绝未使用 .catch() 处理的承诺。要在未处理的 Promise 拒绝时终止节点进程，请使用 CLI 标志 --unhandled-rejections=strict（请参阅 https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode）。 （拒绝编号：1） （节点：16448）[DEP0018] DeprecationWarning：不推荐使用未处理的承诺拒绝。将来，未处理的 Promise 拒绝将使用非零退出代码终止 Node.js 进程。

这是我的文件。当然不用用户名和密码也没关系。

app.js

const express = require('express');
const bodyParser = require('body-parser')
const mongoPractice =require('./mongo')

const app = express();

app.use(bodyParser.json());

app.post('/products',mongoPractice.createProduct);

app.get('/products');

app.listen(3000);

mongo.js

const MongoClient = require("mongodb").MongoClient;

const url ='xxxxxx'

const createProduct = async (req, res, next) => {
    const newProduct = {
      name: req.body.name,
      price: req.body.price
    };
    const client = new MongoClient(url);
  
    try {
      await client.connect();
      const db = client.db();
      const result = db.collection('products').insertOne(newProduct);
    } catch (error) {
      return res.json({message: 'Could not store data.'});
    };
    client.close();
  
    res.json(newProduct);
  };
  
  const getProducts = async (req, res, next) => {
    const client = new MongoClient(url);
  
    let products;
  
    try {
      await client.connect();
      const db = client.db();
      products = await db.collection('products').find().toArray();
    } catch (error) {
      return res.json({message: 'Could not retrieve products.'});
    };
    client.close();
  
    res.json(products);
  };
  
  exports.createProduct = createProduct;
  exports.getProducts = getProducts;

package.json

{
  "name": "refresh-start",
  "version": "1.0.0",
  "description": "",
  "main": "app.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon app.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.19.0",
    "express": "^4.17.1",
    "mongodb": "^4.1.3",
    "nodemon": "^1.19.4"
  }
}

如果我尝试这个 package.json 就可以了，但它已被弃用：

{
  "name": "refresh-start",
  "version": "1.0.0",
  "description": "",
  "main": "app.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "nodemon app.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.19.0",
    "express": "^4.17.1",
    "mongodb": "^3.3.4",
    "nodemon": "^1.19.4"
  }
}

Answer 1

缺少数据库插入的等待前端：

    try {
      await client.connect();
      const db = client.db();
      const result = await db.collection('products').insertOne(newProduct);
    } catch (error) {
      return res.json({message: 'Could not store data.'});
    };
    client.close();
  
    res.json(newProduct);
  };