从 MongoDB Atlas 的集合中获取 NULL 数据

问题描述

限时删除！！

我已使用

1.连接代码 -const 猫鼬 = 要求('猫鼬')const uri = "mongodb+srv://:@cluster0-3awwl.mongodb.net/";猫鼬.connect(uri，{数据库名称:'bing_bot'}).catch((e) => {console.log('数据库连接错误', e)})2.型号-const 猫鼬 = 要求('猫鼬')const Student = mongoose.model('student', {学生姓名: {类型:字符串},接触: {类型:字符串},电子邮件: {类型:字符串},否:{类型:字符串},年: {类型:字符串}})module.exports = Student`在此处输入代码`3. 检索数据 -Student.findById(_id).then((data) => {console.log('数据:', 数据)})4. 使用 MongoClientconst uri = "mongodb+srv://:@cluster0-3awwl.mongodb.net/bing_bot"MongoClient.connect(uri, function(err, client) {如果(错误){console.log('连接到 MongoDB Atlas 时发生错误...\n', err);}console.log('已连接...');const collection = client.db("bing_bot").collection("student");//对集合对象执行操作集合.findOne({学生姓名":测试"}).then((d) => {console.log('数据:', d)})const 数据 = collection.find()控制台日志('数据:1'，数据)客户端关闭()；});

解决方案

这是因为 Connectivity Code 和 Model 中的 mongoose 实例是不同的和不相关的.一个是连接的(Connectivity)，但另一个(模型)不是.您必须使用相同的实例，因此导出一个 mongoose 并在需要的地方导入.

//连接性Code.jsconst 猫鼬 = 要求('猫鼬')const uri = "mongodb+srv://:@cluster0-3awwl.mongodb.net/";猫鼬.connect(uri，{数据库名称:'bing_bot'}).catch((e)=>{console.log('数据库连接错误',e)})module.exports = 猫鼬；//<-- 导出//模型.jsconst mongoose = require('./connectivityCode.js')//<-- 导入//其余代码

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();
});

解决方案

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

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