Getting NULL data from collection from MongoDB Atlas

问题

I have connected my code to MongoDB Atlas using Mongoose... even though the collection has a data in it its shows null in response.

I want to know the exact issue and troubleshoot it, because the collection has the data required

Collection details are in this image:

1. Connectivity Code -
const mongoose = require('mongoose')
const uri = "mongodb+srv://<user>:<password>@cluster0-3awwl.mongodb.net/";
mongoose.connect(uri, {
    dbName: 'bing_bot'
}).catch((e) => {
    console.log('Database connectivity error ', e)
})

2.Model-
const mongoose = require('mongoose')

const Student = mongoose.model('student', {
    StudentName: {
        type:String
    },
    Contact: {
        type:String
    },
    Email: {
        type:String
    },
    BNo: {
        type:String
    },
    Year: {
        type:String
    }
})
 module.exports = Student`enter code here`

3. Retrieve data -
Student.findById(_id).then((data) => {
        console.log('data: ', data)})


4. Using MongoCLient

const uri = "mongodb+srv://<user>:<password>@cluster0-3awwl.mongodb.net/bing_bot"
MongoClient.connect(uri, function(err, client) {
   if(err) {
        console.log('Error occurred while connecting to MongoDB Atlas...\n', err);
   }
   console.log('Connected...');
   const collection = client.db("bing_bot").collection("student");
   // perform actions on the collection object
   collection.findOne({
       "StudentName": "Test"
   }).then((d) => {
       console.log('data: ', d)
   })

   const data = collection.find()
   console.log('data:1 ', data)
   client.close();
});

回答1:

It's because the mongoose instances in your Connectivity Code and Model are different and unrelated. One is connected (Connectivity), but the other (Model) is not. You've to use the same instance so export one mongoose and import that where required.

// connectivityCode.js
const mongoose = require('mongoose')
const uri = "mongodb+srv://<user>:<password>@cluster0-3awwl.mongodb.net/";
mongoose.connect(uri, {
  dbName: 'bing_bot'
}).catch((e)=>{
  console.log('Database connectivity error ',e)
})

module.exports = mongoose; // <-- exporting

// model.js
const mongoose = require('./connectivityCode.js') // <-- importing
// rest of the code

来源：https://stackoverflow.com/questions/55858975/getting-null-data-from-collection-from-mongodb-atlas

标签

node.js

mongodb

heroku

mongoose

mongodb-atlas