错误连接 MongoDB：错误：Route.get() 需要回调函数但得到了 [object Undefined]

Question

我一直在尝试使用express 将我的应用程序连接到MongoDB，但没有成功。下面是代码最重要的部分：

app.js：

var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');
var cors = require('cors');

var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');

var mongoose = require('mongoose');
const bodyParser = require('body-parser');
const vesselController = require('./controllers/VesselController');
require('./config/keys');

var app = express();
app.use(cors());
app.options('*', cors());

// DB Config
const db = require('./config/keys').MongoURI;

const options = {
    useNewUrlParser: true,
    reconnectTries: Number.MAX_VALUE,
    poolSize: 10
};

mongoose
    .connect(db, options)
    .then(() => console.log('MongoDB Connection established'))
    .catch((err) => console.log('Error connecting MongoDB database due to: ', err));

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

// Bodyparser
app.use(express.urlencoded({ extended: false }));

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', indexRouter);
app.use('/users', usersRouter);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
    next(createError(404));
});

app.use((req, res, next) => {
    res.header('Access-Control-Allow-Origin', '*');
    next();
});

// error handler
app.use(function(err, req, res, next) {
    // set locals, only providing error in development
    res.locals.message = err.message;
    res.locals.error = req.app.get('env') === 'development' ? err : {};

    // render the error page
    res.status(err.status || 500);
    res.render('error');
});

const PORT = process.env.PORT || 3000;

app.use(bodyParser.urlencoded({ extended: true, limit: '50mb' }));
app.use(bodyParser.json({ limit: '50mb' }));
app.use(cors());

app.route('/vessels/all').get(vesselController.getBaseAll);
app.route('vessels/:id/track').get(vesselController.getCurrent);
app.route('/vessels').get(vesselController.getHistory);

app.listen(PORT, console.log(`Server started on port ${PORT}`));

module.exports = app;

VesselController.js

const Vessels = require('../models/Vessels');
const Positions = require('../models/Positions');
const Compnanies = require('../models/Companies');

exports.getBaseAll = (req, res) => {
    Promise.all([
        Compnanies.find(),
        Vessels.find(),
        Positions.aggregate([
            {
                $sort: {
                    date: -1
                }
            },
            {
                $group: {
                    _id: '$callsign',
                    details: {
                        $push: '$$ROOT'
                    }
                }
            },
            {
                $replaceRoot: {
                    newRoot: {
                        $arrayElemAt: [ '$details', 0 ]
                    }
                }
            }
        ])
    ])
        .then(([ companies, vessels, positions ]) => {
            // apply vessels detail table as join:
            positions.forEach((pos) => {
                vessels.forEach((ves) => {
                    if (pos.callsign == ves.callsign) {
                        p._detail = ves;
                    }
                });
                companies.forEach((com) => {
                    if (p._detail.company == com.number) {
                        p._detail = com;
                    }
                });
            });
            res.status(200).json(positions);
        })
        .catch((err) => {
            return res.status(500).send(err);
        });
};

exports.getHistory = (req, res) => {
    var id = req.param.id;
    Positions.find(
        {
            callsign: id,
            date: {
                $gte: new Date(Date.now() - 1000 * 60 * 60 * 24)
            }
        },
        (err, task) => {
            if (err) {
                return res.status(500).send(err);
            }
            res.status(200).json(task);
        }
    );
};

exports.getCurrent = (req, res) => {
    var currentPos = Positions.find({
        date: {
            $gte: new Date(Date.now() - 1000 * 60 * 60)
        }
    });
    currentPos.exec((err, task) => {
        if (err) {
            return res.status(500).send(err);
        }
        res.status(200).json(task);
    });
};

我不确定问题是否是由于我正在尝试连接到特定数据库。按如下所示连接到我的应用程序并复制/粘贴密钥后：

mongodb+srv://<username>:<password>@vessel-tracker-cluster-x2lpw.mongodb.net/test?retryWrites=true&w=majority

以下是我的集群的组织方式：

访问集合后，您可以看到数据库的结构：

我做了什么来解决这个问题：

我遇到并分析以解决问题的帖子是：

1) This 很有用，但我无法解决问题。

2) 我使用了this other source，但问题仍然存在。

3) This one 也很有用，但我的问题仍然存在，MongoDB 连接不正确

感谢您指出解决此问题的正确方向。

Answer 1

正如我从堆栈跟踪中看到的，app.js:77:27 中有一个错误：

app.route('/vessels/all').get(vesselController.getBaseAll);

虽然我已经执行了您的代码并且运行良好，但我想向您提出以下建议：

1) 尝试在 VesselController.js 中将 exports 替换为 module.exports；

2) 尝试调试 app.js，看看 vesselController.getBaseAll / vesselController.getCurrent / vesselController.getHistory 返回什么：

console.log(vesselController.getBaseAll); // 应该是[函数]