mongodb - React Fullstack 应用程序显示 mongodb 连接错误

Question

我使用 MERN 堆栈创建了一个简单的 CRUD 应用程序。该应用程序昨天运行良好，但今天当我对前端进行了一些更改并开始运行该应用程序时，它无法正常工作并引发与 mongodb 连接相关的错误。我也可以提供我所有的前端代码（但在运行前端时它没有显示错误）。这是我在后端项目上执行 npm start 时遇到的错误：

[nodemon] restarting due to changes...
[nodemon] starting `node app.js`
Server is running on Port:  4200
App starting error: MongoError: failed to connect to server [localhost:27017] on first connect [MongoError: connect ECONNREFUSED 127.0.0.1:27017]
    at Pool.<anonymous> (/Users/afzaal/expressbackend/node_modules/mongoose/node_modules/mongodb-core/lib/topologies/server.js:328:35)
    at emitOne (events.js:96:13)
    at Pool.emit (events.js:188:7)
    at Connection.<anonymous> (/Users/afzaal/expressbackend/node_modules/mongoose/node_modules/mongodb-core/lib/connection/pool.js:274:12)
    at Connection.g (events.js:292:16)
    at emitTwo (events.js:106:13)
    at Connection.emit (events.js:191:7)
    at Socket.<anonymous> (/Users/afzaal/expressbackend/node_modules/mongoose/node_modules/mongodb-core/lib/connection/connection.js:177:49)
    at Socket.g (events.js:292:16)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:188:7)
    at emitErrorNT (net.js:1281:8)
    at _combinedTickCallback (internal/process/next_tick.js:80:11)
    at process._tickCallback (internal/process/next_tick.js:104:9)
[nodemon] app crashed - waiting for file changes before starting...

这是我的 app.js 文件

var express = require('express');
var app = express();
var mongoose = require('mongoose');
var bodyParser = require('body-parser');
var port = 4200;
var cors = require('cors');

// Mongoose connection with mongodb
mongoose.Promise = require('bluebird');
mongoose.connect('mongodb://localhost:27017/data')//what should I put for the URI?
    .then(() => { // if all is ok we will be here
      console.log('Start');
    })
    .catch(err => { // if error we will be here
        console.error('App starting error:', err.stack);
        process.exit(1);
    });

// Required application specific custom router module
var itemRouter = require('./src/routes/itemRoutes');

// Use middlewares to set view engine and post json data to the server
app.use(cors());
app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());

app.use('/items', itemRouter);

// Start the server
app.listen(port, function(){
  console.log('Server is running on Port: ',port);
});

我确实安装了mongodb。我对 mongodb 很陌生，所以我不确定这是怎么回事。任何帮助是极大的赞赏。

标签： mongodbreactjs