Mongoose findbyid() return null

问题

I am trying to find a record in my mongo db by its id

No matter I use findbyid(), findone(id,...), it return null

here is my code. what is the solution?

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/Movie', {useNewUrlParser: true})
.then(() => console.log('Connected to Databse'))
.catch(err => console.err('Could not connect to MongoDB', err));

var ObjectId = require('mongodb').ObjectID;

const Schema = new mongoose.Schema({
    name: String,
    author: String,
    tags: [String],
    date: Date, 
    isPublished: Boolean,
    price: Number
});

const Data = mongoose.model('Datas', Schema);

async function updateData(id){
const result = await Data.findById(id);
console.log(result);
}
updateData('5a6900fff467be65019a9001');

回答1:

I had the same problem. The _id in my DB collection was a String. After I enabled mongoose debug require('mongoose').set('debug', true), I found out that the mongoose query id as ObjectId("yourId") unless we define _id in the Schema. In order to solve the problem I had to add _id:String in to mongoose schema.

const MyDataSchema = new Schema({
  _id: String,
...
...
}

回答2:

Check your mongodb database, if _id is storaged as String, findById(id) can not found id. FindById(id) only finds ObjectId('yourId'). You might import database by using mongoimport and including _id in JSON, it's wrong, delete _id in imported JSON.

回答3:

There is a simple solution to this:

Replace

const result = await Data.findById(id);

with

const result = await Data.findById(id).exec();

See Mongoose - What does the exec function do? for an explanation on what exec() does

回答4:

Convert the string into ObjectId type before querying

var ObjectID = require('mongodb').ObjectID;   
async function updateData(id){
  const result = await Data.findById(new ObjectID(id));
  console.log(result);
}

refer: this answer.