javascript - 尝试使用 Mongoose 时 MongoClient 未连接错误？

Question

作为我类(class)的一部分，我正在学习 mongodb，现在是 Mongoose。我已经完全按照类(class)中的方式编写了代码，但是当尝试使用 node app.js 启动它时，出现以下错误:

$ node app.js (node:25772) UnhandledPromiseRejectionWarning: MongoNotConnectedError: 必须连接 MongoClient 才能执行此操作 at Object.getTopology (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\node_modules\mongodb\lib\utils.js:391:11) at Collection.insertOne (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\node_modules\mongodb\lib\collection.js:150:61) at NativeCollection.<computed> [as insertOne] (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\drivers\node-mongodb-native\collection.js:200:33) at NativeCollection.Collection.doQueue (C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\collection.js:135:23) at C:\Users\donal\OneDrive\Desktop\Udemy Web Development\FruitsProject\node_modules\mongoose\lib\collection.js:82:24 at processTicksAndRejections (internal/process/task_queues.js:77:11) (Use 节点 --trace-warnings ... to show where the warning was created) (node:25772) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag --unhandled-rejections=strict (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1) (node:25772) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

我在终端的单独选项卡中运行了 mongosh，我尝试了几次搜索来寻找类似的问题。非常欢迎任何帮助!

这是我的完整 app.js 代码:

mongoose.connect("mongodb://localhost:27017/fruitsDB");


const fruitSchema = new mongoose.Schema({
  name: String,
  rating: Number,
  review: String
});

const Fruit = mongoose.model("Fruit", fruitSchema);

const fruit = new Fruit({
  name: "Apple",
  rating: 7,
  review: "Pretty solid as a fruit"
});

fruit.save();
mongoose.connection.close();


const findDocuments = function(db, callback) {

  const collection = db.collection('fruits');

  collection.find({}).toArray(function(err, fruits) {
    assert.equal(err, null);
    console.log("Found the following records");
    console.log(fruits)
    callback(fruits);

  });
}

Answer 1

我遇到了同样的问题，罪魁祸首是在您的 JavaScript 主体中调用 mongoose.connection.close();。正如@AnanthDev 所提到的，mongoose 是异步的，最终会在它能够执行操作之前关闭连接。

以下之所以有效，是因为 mongoose.connection.close() 在回调函数中，并且在执行操作之前不会运行。

Fruit.insertMany([kiwi, orange, banana], function(err) {
    if (err) {
        console.log(err);
    } else {
        mongoose.connection.close();
        console.log("Successfully saved all the fruits to fruitsDB");
    }
})