Question

我正在构建一个使用MongoDB作为后端的快速应用程序，但是当我在应用程序的其他部分向数据库发出请求时，它无法识别。

以下是我所拥有的：

APP.JS（使用Paul的答案）：

var express = require('express');
var app = express();
var bodyParser = require('body-parser');
var cookieParser = require('cookie-parser');
var passport = require('passport');
var mongo = require('mongodb').MongoClient;
var assert = require('assert');

// make mongodb available to the application
app.use((req, res, next) => {
  mongo.connect('mongodb://localhost:27017/formulas', (e, db) => {
  if (e) return next(e);
  req.db = db;
  next();
});

// cleanup
  req.on('end', () => { req.db.close(); });
});

//define routes
var root = require('./routes/index');
var authenticate = require('./routes/authenticate');
var about = require('./routes/about');
var contact = require('./routes/contact');
var formula = require('./routes/formula');
var formulaAPI = require('./routes/api/formula');
var formulaList = require('./routes/formula-list');
var formulaListAPI = require('./routes/api/formula-list');

app.set('view engine', 'ejs');
app.set('views', __dirname + '/views');
app.use(express.static(__dirname + '/public'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));

app.use(root);
app.use(about);
app.use(contact);
app.use(formula);
app.use(formulaAPI);
app.use(formulaList);
app.use(formulaListAPI);
app.use(authenticate);

app.listen(3000, function(){
  console.log("The server is now listening on port 3000");
});

module.exports = app;

当我通过这样的路线呼叫数据库时：

var app = require('express');
var router = app.Router();
var data = require('../data/formula.json');

router.get('/formula-list', function(req, res){
var db = req.db;
db.formulas.find({}, {}, function(e, docs){
  res.render('formula-list', {
    formulas: docs,
    title: 'Your Formulas',
    description: `List of saved user formulas from the formula generator`,
    ID: 'formula-list',
    keywords: 'formula generator, health kismet, nutraceutical formula 
  builder'
  });
});
});

我收到以下错误：

TypeError: Cannot read property 'find' of undefined

当我执行console.log(req.db)时，我在控制台中获得以下内容：

req.db：

EventEmitter {
domain: null,
_events: {},
_eventsCount: 0,
_maxListeners: undefined,
s:
 { databaseName: 'formulas',
 dbCache: {},
 children: [],
 topology:
  EventEmitter {
    domain: null,
    _events: [Object],
    _eventsCount: 7,
    _maxListeners: undefined,
    clientInfo: [Object],
    s: [Object] },
 options:
  { readPreference: [Object],
    promiseLibrary: [Function: Promise] },
 logger: { className: 'Db' },
 bson: {},
 authSource: undefined,
 readPreference:
  { _type: 'ReadPreference',
    mode: 'primary',
    tags: undefined,
    options: undefined },
 bufferMaxEntries: -1,
 parentDb: null,
 pkFactory: undefined,
 nativeParser: undefined,
 promiseLibrary: [Function: Promise],
 noListener: false,
 readConcern: undefined },
 serverConfig: [Getter],
 bufferMaxEntries: [Getter],
 databaseName: [Getter] }

Answer 1

好的，所以在声明需要连接的第一个路由之前，您需要连接中间件以将db连接分配给请求。除非您使用连接池，否则在发送响应后再次释放资源可能是个好主意。

app.use((req, res, next) => {
  mongo.connect('mongodb://localhost:27017/formulas', (e, db) => {
    if (e) return next(e);
    req.db = db;
    next();
  });

  // cleanup
  req.on('end', () => { req.db.close(); });
});

希望有所帮助。

Answer 2

通过documentation on npm，我可以看到要访问特定的集合，这就是你必须要做的事情：

选择要执行操作的集合
执行操作

以下是代码示例：

router.get('/formula-list', function(req, res) {

  // Select the collection on which you want to perform an operation
  var formulas = req.db.collection('formulas');

  // Perform that operation
  formulas.find({}, {}, function(e, docs) {

    res.render('formula-list', {
      formulas: docs,
      title: 'Your Formulas',
      description: `List of saved user formulas from the formula generator`,
      ID: 'formula-list',
      keywords: 'formula generator, health kismet, nutraceutical formula builder'
    });
  });
});

Answer 3

尝试像这样使用

db.collection('collectionName').find({}).toArray(function(e, docs){
  res.render('formula-list', {
    formulas: docs,
    title: 'Your Formulas',
    description: `List of saved user formulas from the formula generator`,
    ID: 'formula-list',
    keywords: 'formula generator, health kismet, nutraceutical formula 
  builder'
  });

}）;

希望它有所帮助。

Answer 4

您需要移动db init代码（在路由定义之前）并将包含mongodb驱动程序的中间件添加到req对象中。类似的东西：

mongo.connect('mongodb://localhost:27017/formulas', function(err, db){
    app.use(function(req, res, next){
        req.db = db;
        next();
    });
});

app.use(root); ...

Answer 5

db.formulas不存在，这是mongo REPL的简写。

在Node.js中，您需要先使用

获取集合

db.collection('name')

这意味着您可以执行以下操作而不是db.formulas.find：

db.collection('formulas').find({}, {}, function(e, docs){})

您也可以这样做：

db.formulas = db.collection('formulas'); db.another = db.collection('another');

然而，最好不要添加＆＃34;魔术代码＆＃34;

MongoDB驱动程序无法识别

5 个答案: