我一直在阅读和阅读，但仍然对在整个NodeJs应用程序之间共享相同数据库（MongoDb）连接的最佳方式感到困惑。据我所知，应用程序启动时应该打开连接，并在模块之间重用。我目前对最佳方法的想法是server.js（一切开始的主文件）连接到数据库并创建传递给模块的对象变量。连接后，模块代码将根据需要使用此变量，此连接将保持打开状态。 E.g：
var MongoClient = require('mongodb').MongoClient;
var mongo = {}; // this is passed to modules and code
MongoClient.connect("mongodb://localhost:27017/marankings", function(err, db) {
if (!err) {
console.log("We are connected");
// these tables will be passed to modules as part of mongo object
mongo.dbUsers = db.collection("users");
mongo.dbDisciplines = db.collection("disciplines");
console.log("aaa " + users.getAll()); // displays object and this can be used from inside modules
} else
console.log(err);
});
var users = new(require("./models/user"))(app, mongo);
console.log("bbb " + users.getAll()); // not connected at the very first time so displays undefined
然后另一个模块models/user看起来像这样：
Users = function(app, mongo) {
Users.prototype.addUser = function() {
console.log("add user");
}
Users.prototype.getAll = function() {
return "all users " + mongo.dbUsers;
}
}
module.exports = Users;
现在我有一种可怕的感觉，这是错误的，所以这种方法有什么明显的问题，如果有的话，如何让它变得更好？
答案 0 :(得分：124)
您可以创建一个mongoUtil.js模块，该模块具有连接到mongo并返回mongo db实例的功能：
const MongoClient = require( 'mongodb' ).MongoClient;
const url = "mongodb://localhost:27017";
var _db;
module.exports = {
connectToServer: function( callback ) {
MongoClient.connect( url, { useNewUrlParser: true }, function( err, client ) {
_db = client.db('test_db');
return callback( err );
} );
},
getDb: function() {
return _db;
}
};
要使用它，您可以在app.js：
var mongoUtil = require( 'mongoUtil' );
mongoUtil.connectToServer( function( err, client ) {
if (err) console.log(err);
// start the rest of your app here
} );
然后，当您需要访问其他地方的mongo时，就像在另一个.js文件中一样，您可以这样做：
var mongoUtil = require( 'mongoUtil' );
var db = mongoUtil.getDb();
db.collection( 'users' ).find();
这样做的原因是，在节点中，当模块为require时，它们只会加载/获取一次，因此您最终只会得到_db的一个实例mongoUtil.getDb()将始终返回相同的实例。
注意，代码未经过测试。
答案 1 :(得分：17)
以下是基于go-oleg的例子，我如何使用现代语法来做到这一点。我的测试和功能。
我在代码中添加了一些注释。
./分贝/ mongodb.js
const MongoClient = require('mongodb').MongoClient
const uri = 'mongodb://user:password@localhost:27017/dbName'
let _db
const connectDB = async (callback) => {
try {
MongoClient.connect(uri, (err, db) => {
_db = db
return callback(err)
})
} catch (e) {
throw e
}
}
const getDB = () => _db
const disconnectDB = () => _db.close()
module.exports = { connectDB, getDB, disconnectDB }
./ index.js
// Load MongoDB utils
const MongoDB = require('./db/mongodb')
// Load queries & mutations
const Users = require('./users')
// Improve debugging
process.on('unhandledRejection', (reason, p) => {
console.log('Unhandled Rejection at:', p, 'reason:', reason)
})
const seedUser = {
name: 'Bob Alice',
email: 'test@dev.null',
bonusSetting: true
}
// Connect to MongoDB and put server instantiation code inside
// because we start the connection first
MongoDB.connectDB(async (err) => {
if (err) throw err
// Load db & collections
const db = MongoDB.getDB()
const users = db.collection('users')
try {
// Run some sample operations
// and pass users collection into models
const newUser = await Users.createUser(users, seedUser)
const listUsers = await Users.getUsers(users)
const findUser = await Users.findUserById(users, newUser._id)
console.log('CREATE USER')
console.log(newUser)
console.log('GET ALL USERS')
console.log(listUsers)
console.log('FIND USER')
console.log(findUser)
} catch (e) {
throw e
}
const desired = true
if (desired) {
// Use disconnectDB for clean driver disconnect
MongoDB.disconnectDB()
process.exit(0)
}
// Server code anywhere above here inside connectDB()
})
./用户/ index.js
const ObjectID = require('mongodb').ObjectID
// Notice how the users collection is passed into the models
const createUser = async (users, user) => {
try {
const results = await users.insertOne(user)
return results.ops[0]
} catch (e) {
throw e
}
}
const getUsers = async (users) => {
try {
const results = await users.find().toArray()
return results
} catch (e) {
throw e
}
}
const findUserById = async (users, id) => {
try {
if (!ObjectID.isValid(id)) throw 'Invalid MongoDB ID.'
const results = await users.findOne(ObjectID(id))
return results
} catch (e) {
throw e
}
}
// Export garbage as methods on the Users object
module.exports = { createUser, getUsers, findUserById }
答案 2 :(得分：16)
如果您使用的是Express，那么您可以使用express-mongo-db模块来允许您在请求对象中获取数据库连接。
安装
npm install --save express-mongo-db
<强> server.js
var app = require('express')();
var expressMongoDb = require('express-mongo-db');
app.use(expressMongoDb('mongodb://localhost/test'));
<强>路由/ users.js
app.get('/', function (req, res, next) {
req.db // => Db object
});
答案 3 :(得分：8)
例如，猫鼬是最常见的之一。这就是我们在初始server.js文件中的内容：
const mongoose = require('mongoose');
const options = {server: {socketOptions: {keepAlive: 1}}};
mongoose.connect(config.db, options);
这就是设置它所需要的一切。现在在代码中的任何位置使用它
const mongoose = require('mongoose');
您可以使用mongoose.connect
答案 4 :(得分：6)
将连接初始化为承诺：
const MongoClient = require('mongodb').MongoClient
const uri = 'mongodb://...'
const client = new MongoClient(uri)
const connection = client.connect() // initialized connection
然后在希望对数据库执行任何操作时调用连接：
// if I want to insert into the database...
const connect = connection
connect.then(() => {
const doc = { id: 3 }
const db = client.db('database_name')
const coll = db.collection('collection_name')
coll.insertOne(doc, (err, result) => {
if(err) throw err
})
})
答案 5 :(得分：6)
这是我在2020年的设置：
./ utils / database.js
const { MongoClient } = require('mongodb');
class Mongo {
constructor () {
this.client = new MongoClient("mongodb://127.0.0.1:27017/my-app", {
useNewUrlParser: true,
useUnifiedTopology: true
});
}
async main () {
await this.client.connect();
console.log('Connected to MongoDB');
this.db = this.client.db();
}
}
module.exports = new Mongo();
/app.js
const mongo = require('./utils/database');
const express = require('express');
const app = express();
const boot = async () => {
await mongo.main();
app.listen(3000);
};
boot();
答案 6 :(得分：4)
基于已接受答案的经过测试的解决方案：
mongodbutil.js：
var MongoClient = require( 'mongodb' ).MongoClient;
var _db;
module.exports = {
connectToServer: function( callback ) {
MongoClient.connect( "<connection string>", function( err, client ) {
_db = client.db("<collection name>");
return callback( err );
} );
},
getDb: function() {
return _db;
}
};
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 app = express();
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');
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')));
var mongodbutil = require( './mongodbutil' );
mongodbutil.connectToServer( function( err ) {
//app goes online once this callback occurs
var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');
var companiesRouter = require('./routes/companies');
var activitiesRouter = require('./routes/activities');
var registerRouter = require('./routes/register');
app.use('/', indexRouter);
app.use('/users', usersRouter);
app.use('/companies', companiesRouter);
app.use('/activities', activitiesRouter);
app.use('/register', registerRouter);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
next(createError(404));
});
// error handler
app.use(function(err, req, res, next) {
res.locals.message = err.message;
res.locals.error = req.app.get('env') === 'development' ? err : {};
res.status(err.status || 500);
res.render('error');
});
//end of calback
});
module.exports = app;
activities.js - 路线：
var express = require('express');
var router = express.Router();
var mongodbutil = require( '../mongodbutil' );
var db = mongodbutil.getDb();
router.get('/', (req, res, next) => {
db.collection('activities').find().toArray((err, results) => {
if (err) return console.log(err)
res.render('activities', {activities: results, title: "Activities"})
});
});
router.post('/', (req, res) => {
db.collection('activities').save(req.body, (err, result) => {
if (err) return console.log(err)
res.redirect('/activities')
})
});
module.exports = router;
答案 7 :(得分：4)
因为这是用Express标记的，所以我想我想说一下Express具有内置功能，可在路线之间共享数据。有一个名为app.locals的对象。我们可以将属性附加到它并从我们的路线内部访问它。您只需在app.js文件中实例化mongo连接即可。
var app = express();
MongoClient.connect('mongodb://localhost:27017/')
.then(client =>{
const db = client.db('your-db');
const collection = db.collection('your-collection');
app.locals.collection = collection;
});
// view engine setup
app.set('views', path.join(__dirname, 'views'));
现在可以在下面的路由中访问此数据库连接，而无需创建和需要其他模块。
app.get('/', (req, res) => {
const collection = req.app.locals.collection;
collection.find({}).toArray()
.then(response => res.status(200).json(response))
.catch(error => console.error(error));
});
此方法可确保您在应用程序运行期间一直打开数据库连接，除非您选择随时关闭它。通过req.app.locals.your-collection可以轻松访问它，并且不需要其他模块。
答案 8 :(得分：4)
我来晚了，但是希望这个答案对某人有帮助，这是一个功能代码：
const MongoClient = require("mongodb").MongoClient
const urlMongo = "mongodb://localhost:27017"
var db;
function connectToServer( callback ) {
MongoClient.connect(urlMongo, { useUnifiedTopology: true , useNewUrlParser: true }, function( err, client ) {
db = client.db('auth');
return callback( err );
})
}
function getDb() {
return db
}
module.exports = {connectToServer, getDb}
我们导出一个函数以连接到mongo，并导出另一个函数以获取连接的实例。
const express = require('express')
const app = express()
const mongo = require('./db.js');
mongo.connectToServer( function( err) {
if (err) console.log(err);
const auth = require('./modulos')
app.post('/login', (req, res) => { auth.login(req, res)})
app.listen(3000, function () { console.log('Corriendo en puerto 3000')})
});
初始化连接后，必须执行auth模块的要求，否则getDb函数将返回undefined。
const db = require('../db.js').getDb()
const usuariosCollection = db.collection('usuarios')
function login(req, res){
usuariosCollection.find({ 'username': 'Fran' }).toArray(function (err, doc) {
...
})
}
答案 9 :(得分：3)
可以通过多种方式对此进行调整，以在适当的地方接受配置对象，但是总体而言，这与布局代码的方式类似，尽管使用了更现代的JS语法。如果您需要的话，可以很容易地将其重写为原型和回调。
mongo.js
from mlarray import double, single, uint8, ...Users.js
lokyapp.js
const { MongoClient } = require('mongodb');
const config = require('./config');
const Users = require('./Users');
const conf = config.get('mongodb');
class MongoBot {
constructor() {
const url = `mongodb://${conf.hosts.join(',')}`;
this.client = new MongoClient(url, conf.opts);
}
async init() {
await this.client.connect();
console.log('connected');
this.db = this.client.db(conf.db);
this.Users = new Users(this.db);
}
}
module.exports = new MongoBot();
someFile.js
class User {
constructor(db) {
this.collection = db.collection('users');
}
async addUser(user) {
const newUser = await this.collection.insertOne(user);
return newUser;
}
}
module.exports = User;
答案 10 :(得分：2)
我们可以创建dbconnection.js之类的dbconnection文件
const MongoClient = require('mongodb').MongoClient
const mongo_url = process.env.MONGO_URL;
module.exports = {
connect: async function(callback) {
var connection;
await new Promise((resolve, reject) => {
MongoClient.connect(mongo_url, {
useNewUrlParser: true
}, (err, database) => {
if (err)
reject();
else {
connection = database;
resolve();
}
});
});
return connection;
}
};
，然后在您的应用中使用该文件，例如
var connection = require('../dbconnection');
然后在异步函数中使用
db = await connection.connect();
希望这会起作用
答案 11 :(得分：2)
如果您选择在应用程序中使用猫鼬，请使用以下代码段编辑app.js文件
app.js
const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/Your_Data_Base_Name', {useNewUrlParser:true})
.then((res) => {
console.log(' ########### Connected to mongDB ###########');
})
.catch((err) => {
console.log('Error in connecting to mongoDb' + err);
});`
下一步： 例如，为您的应用程序定义模型需要它们并直接执行CRUD操作
blogSchema.js
const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const blogSchema = new Schema({
_id : mongoose.Schema.Types.ObjectId,
title : {
type : 'String',
unique : true,
required : true
},
description : String,
comments : [{type : mongoose.Schema.Types.ObjectId, ref: 'Comment'}]
});
module.exports = mongoose.model('Blog', blogSchema);
用法 createBlog.js
const Blog = require('../models/blogSchema');
exports.createBlog = (req, res, next) => {
const blog = new Blog({
_id : new mongoose.Types.ObjectId,
title : req.body.title,
description : req.body.description,
});
blog.save((err, blog) => {
if(err){
console.log('Server Error save fun failed');
res.status(500).json({
msg : "Error occured on server side",
err : err
})
}else{
//do something....
}
您不必总是连接到mogoDB ....
答案 12 :(得分：1)
var MongoClient = require('mongodb').MongoClient;
var url = 'mongodb://localhost:27017/';
var Pro1;
module.exports = {
DBConnection:async function()
{
Pro1 = new Promise(async function(resolve,reject){
MongoClient.connect(url, { useNewUrlParser: true },function(err, db) {
if (err) throw err;
resolve(db);
});
});
},
getDB:async function(Blockchain , Context)
{
bc = Blockchain;
contx = Context;
Pro1.then(function(_db)
{
var dbo = _db.db('dbname');
dbo.collection('collectionname').find().limit(1).skip(0).toArray(function(err,result) {
if (err) throw err;
console.log(result);
});
});
},
closeDB:async function()
{
Pro1.then(function(_db){
_db.close();
});
}
};
答案 13 :(得分：1)
<!DOCTYPE html>
<html>
<head>
<title>HTML Tables</title>
</head>
<body>
<table border = "1">
<tr>
<td><p><span>Row 1, Column 1, This should be kept because it has more than two tokens</span></p></td>
<td><p><span>not kept</span></p></td>
</tr>
<tr>
<td><p><span>Row 2, Column 1, should be kept</span></p></td>
<td><p><span>Row 2, Column 2, should be kept</span></p></td>
</tr>
</table>
</body>
</html>
答案 14 :(得分：1)
我发现这很好用：）
mongoUtil.ts
import { MongoClient } from 'mongodb';
const uri =
'MONGOSTRING';
let connPoolPromise: any = null;
const mongoPoolPromise = () => {
if (connPoolPromise) return connPoolPromise;
connPoolPromise = new Promise((resolve, reject) => {
const conn = new MongoClient(uri, {
useNewUrlParser: true,
useUnifiedTopology: true,
});
if (conn.isConnected()) {
return resolve(conn);
} else {
conn
.connect()
.then(() => {
return resolve(conn.db('DATABASENAME'));
})
.catch(err => {
console.log(err);
reject(err);
});
}
});
return connPoolPromise;
};
export = {
mongoPoolPromise,
};
anyFile.ts
const { mongoPoolPromise } = require('./mongoUtil');
async function getProducts() {
const db = await mongoPoolPromise();
const data = await db
.collection('myCollection')
.find({})
.toArray();
console.log(data);
return data;
}
export { getProducts };
答案 15 :(得分：1)
为此我有点迟了，但我也会添加解决方案。与这里的答案相比，这是一种更加笨拙的方法。
无论如何，如果您使用的是MongoDB 4.0版和Node.js 3.0（或更高版本），则可以使用MongoClient中的isConnected()函数。
const MongoClient = require('mongodb').MongoClient;
const uri = "<your connection url>";
const client = new MongoClient(uri, { useNewUrlParser: true });
if (client.isConnected()) {
execute();
} else {
client.connect().then(function () {
execute();
});
}
function execute() {
// Do anything here
// Ex: client.db("mydb").collection("mycol");
}
这对我来说很好。希望对您有所帮助。
答案 16 :(得分：0)
基于公认的答案，我使用一种简单的方法。但是，仅当您要在一段时间后执行的内部函数中使用db时，才使用此函数。例如：在快速航线功能中，这是您可以采用的最简单的方法。
mongo.js
const MongoClient = require("mongodb").MongoClient
var db
const connectDb = (callback) => {
if (db) return callback()
MongoClient.connect( uri, {ops},
(err, database) => {
if (err) return console.log(err)
db = database.db("dbName")
console.log("Database Connected")
callback()
}
)
}
const getDb = (collectionToGet) => {
return db.collection(collectionToGet)
}
module.exports = {
connectDb,
getDb,
}
现在，在需要db对象的其他文件中，
user.js
const { connectDb, getDb } = require('mongo.js')
var db // store db object in this object
connectDb(() => ( db = getDb("user") ))
app.get('/', (req, res) => {
// do something with req
db.insert({})
// do something with res
}
答案 17 :(得分：0)
您可以使用Singleton Design Pattern来实现MongoDB连接的跨文件使用。
Init.mjs
/* ################ Controller ################ */
import ctrlLib from '../../controller/lib.mjs';
/* ################ MongoDB ################ */
import mongodb from 'mongodb';
/* ################ Logs ################ */
import log from 'fancy-log';
import chalk from 'chalk';
/** Init MongoDB connection */
export class Init {
/**
* Check if its first time usage of this class.
If true set class instance to this that we always get same instance.
* Then get MongoDB details from config.yml and set as global.
* In the last step we return the class instance.
*/
constructor() {
if (Init.instance == null) Init.instance = this;
const config = ctrlLib.getConfig();
this.MongoURL = config.MongoDB.url;
this.MongoName = config.MongoDB.dbname;
({MongoClient: this.MongoClient} = mongodb);
return Init.instance;
}; // constructor(){
/** Connect to Database and return connection */
async connect() {
try {
const client = await this.MongoClient.connect(
this.MongoURL, {useNewUrlParser: true, useUnifiedTopology: true},
);
this.connection = {'db': client.db(this.MongoName), 'client': client};
return this.connection;
} // try {
catch (e) {
log( `${chalk.red.bold('❌ ERROR')} while try to connect to MongoDB DB
${chalk.white.bold('Error:\n')} ${e}` );
} // catch (e) {
}; // async connect() {
/**
* Return connection for cross file usage
* @return {object}
*/
getConnection() {return this.connection;};
}; // export class Init {
app.mjs
/* ################ Services ################ */
import {Init} from './Init.mjs';
(async ()=>{
await new Init().connect();
})().catch(e=>{log('app.mjs - Catch error: ' + e);});
anyOtherFile.mjs
/* ################ Services ################ */
import {Init} from './Init.mjs';
/** Subclass of Search which contains lib functions */
class Lib {
/**
* Find data by using search query and return result.
* @param {string} collection - Name of collection
* @param {object} query - Search query
*/
async findOne(collection, query) {
const connection = new Init().getConnection();
return await connection.db.collection(collection).findOne(query);
}; // async findOne() {
}; // class Lib {