如何使 MongoDB 在 Express 的 HTTP 方法中可用？

Question

我正在尝试将 MongoDB 与 Node/Express 一起使用。我使official example 工作：

var express = require('express')
var MongoClient = require('mongodb').MongoClient
var assert = require('assert')
var app = express()

// Connection URL
var url = 'mongodb://localhost:27017/myproject'
// Use connect method to connect to the Server
MongoClient.connect(url, function(err, db) {
  assert.equal(null, err)
  console.log("Connected correctly to server")

  insertDocuments(db, function() {
    db.close()
  })
})

var insertDocuments = function(db, callback) {
  // Get the documents collection
  var collection = db.collection('documents')
  // Insert some documents
  collection.insertMany([
    // Some code
  ], function(err, result) {
    // Some code
    callback(result)
  })
}

app.get('/insert-document', function(req, res) {
  // res.send()
})

我怎样才能让 Mongo 在 Express 的 HTTP 方法中可用？例如，在app.get('/insert-document', function(req, res) 中使用insertDocuments()？

编辑（完整的server.js 文件）：

var express = require('express')
// var PouchDB = require('pouchdb')
var MongoClient = require('mongodb').MongoClient
var assert = require('assert')
var webpack = require('webpack')
var config = require('./webpack.dev.conf')

var app = express()
var compiler = webpack(config)

// Connection URL
var url = 'mongodb://localhost:27017/myproject'
// Use connect method to connect to the Server
var db

MongoClient.connect(url, function(err, db) {
  assert.equal(null, err)
  console.log("Connected correctly to server")
  db = db
})

var insertDocuments = function(db, callback) {
  // Get the documents collection
  var collection = db.collection('documents')
  // Insert some documents
  collection.insertMany([
    {a : 1}, {a : 2}, {a : 3}
  ], function(err, result) {
    assert.equal(err, null)
    assert.equal(3, result.result.n)
    assert.equal(3, result.ops.length)
    console.log("Inserted 3 documents into the document collection")
    callback(result)
  })
}

// handle fallback for HTML5 history API
app.use(require('connect-history-api-fallback')())

// serve webpack bundle output
app.use(require('webpack-dev-middleware')(compiler, {
  publicPath: config.output.publicPath,
  stats: {
    colors: true,
    chunks: false
  }
}))

// enable hot-reload and state-preserving
// compilation error display
app.use(require('webpack-hot-middleware')(compiler))

app.get('/docs', function(req, res) {
  // res.send()
  insertDocuments(db, function() {
    db.close()
  })
})

app.listen(8080, 'localhost', function (err) {
  if (err) {
    console.log(err)
    return
  }
  console.log('Listening at http://localhost:8080')
})

我明白了

TypeError：无法读取未定义的属性“集合” 在 insertDocuments (/home/alex/node/project-mongo/build/dev-server.js:24:22)

Answer 1

参考代码here，将连接db保存为一个全局变量，示例代码如下。

var db;

MongoClient.connect(url, function(err, db) {
      assert.equal(null, err)
      console.log("Connected correctly to server")

      db = db;
      // Start the application after the database connection is ready
      app.listen(3000);
      console.log("Listening on port 3000");
});

// Reuse database object in request handlers
app.get('/insert-document', function(req, res) {
      // insertDocuments() could invoked here.
});