如何使用 TypeScript 编写的 Node.js 连接到 MongoDB？

Question

我在 Node.js 服务器上工作，连接到 MongoDB 并用 TypeScript 编写。当我尝试使用 MongoDB 时，它不会创建连接，但是当我检查 mongo 输出时，它似乎确实创建了连接。

我在代码中缺少什么来定义 Node.js 中的连接？

我的连接字符串是 'mongodb://localhost:27017'

我的连接方法：

connect() {
    console.log('connecting to mongo') //this is called
    MongoClient.connect(this.connectionString, {useNewUrlParser: true})
    .then(client => {
        console.log('setting client'); //this doesn't get called
        this.client = client;
        console.log(this.client);
    })
    .catch(error => {
        console.log('error during connecting to mongo: '); //this also doesn't get called
        console.error(error);
    });
}

蒙戈输出：

2018-11-08T23:06:24.106+0100 I NETWORK [listener] 连接从 127.0.0.1:51345 #11 接受（现在打开 2 个连接）

2018-11-08T23:06:24.107+0100 I NETWORK [conn11] 从 127.0.0.1:51345 conn11: { driver: { name: "nodejs", version: "3.1.9" }, os: { type ：“达尔文”，名称：“达尔文”，架构：“x64”，版本：“17.7.0”}，平台：“Node.js v8.9.3，LE，mongodb-core：3.1.8”}

我的存储库位于https://github.com/FrisoDenijs/MEAN-ToDo/blob/master/server/src/db/mongo.db.ts以获得完整代码。

console.log(db) 正如 shkaper 所问

MongoClient {
  domain: null,
  _events: {},
  _eventsCount: 0,
  _maxListeners: undefined,
  s:
   { url: 'mongodb://localhost:27017',
     options:
      { servers: [Array],
        caseTranslate: true,
        useNewUrlParser: true,
        socketTimeoutMS: 360000,
        connectTimeoutMS: 30000,
        promiseLibrary: [Function: Promise] },
     promiseLibrary: [Function: Promise],
     dbCache: {},
     sessions: [] },
  topology:
   Server {
     domain: null,
     _events:
      { serverOpening: [Function],
        serverDescriptionChanged: [Function],
        serverHeartbeatStarted: [Function],
        serverHeartbeatSucceeded: [Function],
        serverHeartbeatFailed: [Function],
        serverClosed: [Function],
        topologyOpening: [Function],
        topologyClosed: [Function],
        topologyDescriptionChanged: [Function],
        commandStarted: [Function],
        commandSucceeded: [Function],
        commandFailed: [Function],
        joined: [Function],
        left: [Function],
        ping: [Function],
        ha: [Function],
        authenticated: [Function],
        error: [Function],
        timeout: [Function],
        close: [Function],
        parseError: [Function],
        open: [Object],
        fullsetup: [Object],
        all: [Object],
        reconnect: [Function] },
     _eventsCount: 25,
     _maxListeners: Infinity,
     clientInfo:
      { driver: [Object],
        os: [Object],
        platform: 'Node.js v8.9.3, LE' },
     s:
      { coreTopology: [Object],
        sCapabilities: null,
        clonedOptions: [Object],
        reconnect: true,
        emitError: true,
        poolSize: 5,
        storeOptions: [Object],
        store: [Object],
        host: 'localhost',
        port: 27017,
        options: [Object],
        sessionPool: [Object],
        sessions: [],
        promiseLibrary: [Function: Promise] } } }

Answer 1

问题是因为mongo.connect异步代码和控制器错误地调用了它。所以后续行将mongo.getDb()在没有this.client正确启动的情况下执行。

由于您使用 Typescript，我们可以使用async/await更干净的代码。

async connect() { // add async
    console.log('connecting to mongo');

    try {
      if (!this.client) { // I added this extra check
        console.log('setting client');
        this.client = await MongoClient.connect(this.connectionString, { useNewUrlParser: true })
        console.log(this.client);      
      }
    } catch(error) {
      console.log('error during connecting to mongo: ');
      console.error(error);
    }    
}

在控制器代码中

async get(req: Request, res: Response) { // add async
  const mongo = new MongoDb();
  await mongo.connect(); // add await
  const db = mongo.db(); 
  // ....     
}

我用更改尝试了你的 repo 并得到了这个回复

希望能帮助到你