Use MongoDB with Node.JS - Knowledgebase - Resilient Cyber Solutions, LLC

Introduction

Node.js is a runtime environment and server-side scripting language used to build highly scalable and responsive applications like blogs, e-commerce websites, and corporate portals. MongoDB, like other NoSQL databases, is non-tabular. This means it stores data differently than relational databases and has data types like document, key-value, wide-column, and graph. It has a flexible schema and scales easily.

You can use the power of Node.js and MongoDB to build modern data-driven applications. This guide shows you how to implement a sample application using the Node.js MongoDB driver on Ubuntu 20.04 server.

Prerequisites

To follow along with this guide:

1. Set a MongoDB Database

In this guide, the sample application permanently stores documents (records) in a MongoDB collection. Follow the following steps to initialize the database and insert some sample documents:

Log in to the MongoDB server using the administrator account credentials. Replace mongo_db_admin with the correct username.
```
$ mongosh -u mongo_db_admin -p --authenticationDatabase admin
```
Enter your MongoDB password and press ENTER to proceed.

Output.
```
test>
```
Run the following use command to create a sample my_company database.
```
test> use my_company
```
Output.
```
switched to db my_company
```

Create a new employees collection and insert three sample documents into the document by running the following command.

my_company> db.employees.insertMany([{
                "employee_id" : 1,
                "first_name" : "JOHN",
                "last_name" : "DOE"
            },
            {
                "employee_id" : 2,
                "first_name" : "MARY",
                "last_name" : "SMITH"
            },
            {
                "employee_id" : 3,
                "first_name" : "DAVID",
                "last_name" : "JACK"
            }]);

Output.

{
  acknowledged: true,
  insertedIds: {
    '0': ObjectId("62f6088b1c072dfeff3a41b8"),
    '1': ObjectId("62f6088b1c072dfeff3a41b9"),
    '2': ObjectId("62f6088b1c072dfeff3a41ba")
  }
}

Query the employees collection to ensure the documents are in place.

my_company> db.employees.find()

Output.

[
  {
    _id: ObjectId("62f6088b1c072dfeff3a41b8"),
    employee_id: 1,
    first_name: 'JOHN',
    last_name: 'DOE'
  },
  {
    _id: ObjectId("62f6088b1c072dfeff3a41b9"),
    employee_id: 2,
    first_name: 'MARY',
    last_name: 'SMITH'
  },
  {
    _id: ObjectId("62f6088b1c072dfeff3a41ba"),
    employee_id: 3,
    first_name: 'DAVID',
    last_name: 'JACK'
  }
]

Log out from the MongoDB server.
```
my_company> quit
```

After setting up the database and inserting the sample records, proceed to the next step and create a database class that allows you to interact with the MongoDB database inside a Node.js code.

2. Create a `mongo_db_gateway` Class

Every Node.js application requires a separate directory to avoid mixing the source code and system files. You should put all your application files inside that directory. For this application, you should start by coding a mongo_db_gateway.js file. This class file hosts methods for managing the database connection and performing other operations like inserting, finding, updating, and deleting documents.

Start by creating a new project directory.
```
$ mkdir project
```
Navigate to the new project directory.
```
$ cd project
```
Open a new mongo_db_gateway.js file in a text editor.
```
$ nano mongo_db_gateway.js
```

Enter the following information into the mongo_db_gateway.js file. Replace the dbPass value (EXAMPLE_PASSWORD) with the correct MongoDB password.

class mongo_db_gateway {

    connect(callBack) {

        const MongoClient = require('mongodb').MongoClient;

        const dbHost = 'localhost';
        const dbUser = 'mongo_db_admin';
        const dbPass = 'EXAMPLE_PASSWORD';
        const dbPort = 27017;
        const dbName = "my_company";

        const conString = "mongodb://" + dbUser + ":" + dbPass + "@" + dbHost + ":" + dbPort;

        MongoClient.connect(conString, function(err, dbClient) {

            if (!err) {
                const mongoDb = dbClient.db(dbName);
                callBack(null, mongoDb);
            }
        });
    }

    insertDocument(data, callBack) {

        this.connect(function (dbErr, mongoDb) {

            if (!dbErr) {

                mongoDb.collection("employees").insertOne(data, function(err, result) {
                    if (err) {
                        callBack(err, null);
                    } else {
                        callBack(null, result);
                    }
                });
            }
        });
    }

    findDocuments(resourceId, callBack) {

        this.connect(function (dbErr, mongoDb) {

            if (!dbErr) {

                var query = {};

                if (resourceId != "") {
                    query = {"employee_id": parseInt(resourceId)};
                }

                mongoDb.collection("employees").find(query).toArray(function(err, result) {
                    if (err) {
                        callBack(err, null);
                    } else {
                        callBack(null, result);
                    }
                });
            }
        });
    }

    updateDocument(resourceId, data, callBack) {

        this.connect(function (dbErr, mongoDb) {

            if (!dbErr) {

                var query = {"employee_id": parseInt(resourceId)};

                data = {$set: data};

                mongoDb.collection("employees").updateOne(query, data, function(err, result) {
                    if (err) {
                        callBack(err, null);
                    } else {
                        callBack(null, result);
                    }
                });
            }
        });
    }

    deleteDocument(resourceId, callBack) {

        this.connect(function (dbErr, mongoDb) {

            if (!dbErr) {

                var query = {"employee_id": parseInt(resourceId)};

                mongoDb.collection("employees").deleteOne(query, function(err, result) {
                    if (err) {
                        callBack(err, null);
                    } else {
                        callBack(null, result);
                    }
                });
            }
        });
    }
}

module.exports = mongo_db_gateway;

Save and close the mongo_db_gateway.js file.

The mongo_db_gateway.js file explained:

The mongo_db_gateway.js class file contains five methods illustrated below.

   class mongo_db_gateway {

       connect(callBack) {
           ...
       }

       insertDocument(data, callBack) {
           ...
       }

       findDocuments(resourceId, callBack) {
           ...
       }

       updateDocument(resourceId, data, callBack) {
           ...
       }

       deleteDocument(resourceId, callBack) {
           ...
       }

   }

The functions of the five different methods are as follows:
- connect(): This method uses database credentials to connect to the MongoDB database using the MongoClient.connect() function.
- insertDocument(data, callBack): This methods accepts two arguments. The data argument is a JSON payload from the HTTP client requesting to insert a document into the employees collection. The callBack argument is a special function that runs when the insertDocument(...) function completes. The mongoDb.collection("employees").insertOne(..) statement is the actual function that inserts the data into the MongoDB database.
- findDocuments(resourceId, callBack): This function is like the SQL SELECT * FROM SAMPLE_TABLE WHERE CONDITION = SOME_VALUE statement. The findDocuments() function accepts two values. The resourceId is the employee_id for the employee you want to return from the collection. The callBack argument is a function that runs when the code executes. Under the findDocuments(...) function, you're examining the value of the resourceId to craft the suitable query for the mongoDb.collection("employees").find(query).toArray(...) function as illustrated below. An empty filter ({}) query returns all documents in the collection. Otherwise, the {"employee_id": parseInt(resourceId)} filter query returns a specific document.
```
  ...
  var query = {};

  if (resourceId != "") {
     query = {"employee_id": parseInt(resourceId)};
  }

  mongoDb.collection("employees").find(query).toArray(...)
  ...
```
- updateDocument(resourceId, data, callBack): The updateDocument(...) function takes three arguments. The resourceId argument defines a filter for the document you want to update. The data is a JSON payload with new document values. The callBack argument is a function that the updateDocument(...) function calls after completion. The updateDocument(...) function runs the mongoDb.collection("employees").updateOne(query, data, ... function to update the document matching the filter query.
- deleteDocument(resourceId, callBack): The deleteDocument(...) function takes two arguments. The resourceId argument allows you to craft a filter query to delete a document per the following illustration.
```
  ...
  var query = {"employee_id": parseInt(resourceId)};

  mongoDb.collection("employees").deleteOne(query...)
  ...
```
The module.exports = mongo_db_gateway; line at the end of the mongo_db_gateway.js file allows you to import the module in other Node.js files using the require('./mongo_db_gateway.js') statement.

Your mongo_db_gateway.js module is now ready. The next step shows you how to call the mongo_db_gateway class methods to insert, find, update, and delete documents.

3. Create an `index.js` File

Every Node.js application requires an entry point that executes when the application starts. This guide uses an index.js file as the entry point. Follow the steps below to create the file:

Open a new index.js file in a text editor.
```
$ nano index.js
```

Enter the following information into the index.js file.

const http = require('http');
const url  = require("url");
const mongo_db_gateway = require('./mongo_db_gateway');

const httpHost = '127.0.0.1';
const httpPort = 8080;

const httpServer = http.createServer(httpHandler);

httpServer.listen(httpPort, httpHost, () => {
    console.log(`HTTP server running at http://${httpHost}:${httpPort}/`);
});

function httpHandler(req, res) {

    var pathname = url.parse(req.url).pathname;
    var resourcePath = pathname.split("/");

    resourceId   = "";

    if (resourcePath.length >= 3) {
        resourceId = resourcePath[2]
    }

    const dg = new mongo_db_gateway();

    switch (req.method) {

        case "POST":

            var jsonData = "";

            req.on('data', function (data) {
                jsonData += data;
            });

            req.on('end', function () {
                dg.insertDocument(JSON.parse(jsonData), callBack);
            });

            break;

        case "PUT":

            var jsonData = "";

            req.on('data', function (data) {
                jsonData += data;
            });

            req.on('end', function () {
                dg.updateDocument(resourceId, JSON.parse(jsonData), callBack);
            });

            break;

        case "DELETE":

            dg.deleteDocument(resourceId, callBack);

            break;

        case "GET":

            dg.findDocuments(resourceId, callBack);

            break;
    }

    function callBack(err, result) {

        res.writeHead(200, {'Content-Type': 'application/json'});

        if (!err) {
            res.write(JSON.stringify(result, null, 4));
        } else {
            res.write(err);
        }

        res.end();
    }
}

Save and close the index.js file.

The index.js file explained:

The first three lines in the index.js file import the modules required to run this sample application together with the custom mongo_db_gateway.js module you coded earlier. The http module provides HTTP functionalities to your application and allows you to use and run the Node.js inbuilt web server. The url module splits the web address into different parts and returns a resource path.
```
const http = require('http');
const url  = require("url");
const mongo_db_gateway = require('./mongo_db_gateway');

...
```
The following two lines define the address and port for the HTTP server.
```
...

const httpHost = '127.0.0.1';
const httpPort = 8080;

...
```
The following line defines a new HTTP server and specifies a callback function (httpHandler).
```
...
const httpServer = http.createServer(httpHandler);
...
```

The line below instructs the web server to listen for incoming HTTP requests and print a message on the console when the code runs.

...

httpServer.listen(httpPort, httpHost, () => {
    console.log(`HTTP server running at http://${httpHost}:${httpPort}/`);
});

...

The following line defines a httpHandler(req, res) {...} function.
```
...
httpHandler(req, res) {
    ...
}
...
```
The following lines retrieve the resourceId from the request URL. For instance, when an HTTP client requests the http://127.0.0.1:8080/employees/4 URL, the logic below retrieves 4 as a resourceId. You're using the resourceId value to find, update, and delete documents by crafting a search filter that MongoDB understands.
```
    ...
    var pathname = url.parse(req.url).pathname;
    var resourcePath = pathname.split("/");

    resourceId   = "";

    if (resourcePath.length >= 3) {
        resourceId = resourcePath[2]
    }
    ...
```
The next line in the index.js file initializes the mongo_db_gateway module you created earlier. Then, you're using the Node.js switch(...){...} statement to map the HTTP req.methods (POST, GET, PUT, and DELETE) to the corresponding database functions (dg.insertDocument(...), dg.getDocuments(...), dg.updateDocument(...), and dg.deleteDocument(...)).
```
    ...

    const dg = new mongo_db_gateway();

    switch (req.method) {
       ...
    }
    ...
```

The callBack() function towards the end of the index.js file runs when MongoDB completes the database operations. Then, you're using the res.write(JSON.stringify(result, null, 4)); statement to write a response to the calling HTTP client.

    ...

    function callBack(err, result) {

        res.writeHead(200, {'Content-Type': 'application/json'});

        if (!err) {
            res.write(JSON.stringify(result, null, 4));
        } else {
            res.write(err);
        }

        res.end();
    }
    ...

You now have all the source code files required to run your application. The next step focuses on testing your application.

4. Test the Application

After creating the MongoDB database and coding all the source code files, your application is now ready for testing. Follow the steps below to test the application:

Ensure you have got the latest npm version.

$ sudo npm install npm -g

Output.

changed 41 packages, and audited 206 packages in 4s

...

found 0 vulnerabilities

Use npm to initialize your project directory.
```
$ npm init
```

Enter the following responses when prompted.

package name: (project) project ENTER
version: (1.0.0) 1.0.0 ENTER
description: Node.js and MongoDB ENTER
entry point: (index.js) index.js ENTER
test command: ENTER
git repository: ENTER
keywords: Node.js, MongoDB ENTER
author: Test author ENTER
license: (ISC) ENTER

About to write to ...package.json:
...

Is this OK? (yes) yes

Install the MongoDB Node.js driver module (mongodb).
```
$ npm install mongodb
```
Run the application. Remember, index.js is the entry point to your application.
```
$ node index.js
```
The application starts a web server and displays the output below. Don't enter any other command in your active terminal window.
```
HTTP server running at http://127.0.0.1:8080/
```

Establish another SSH connection to your server and use the Linux curl command to run the following test commands.

Create a new document:

$ curl -X POST http://127.0.0.1:8080/employees -H 'Content-Type: application/json' -d '{"employee_id": 4, "first_name": "HENRY", "last_name": "JACKSON"}'

Output.

{
    "acknowledged": true,
    "insertedId": "62f77136ebf1445162cbd181"
}

Retrieve all documents:

$ curl -X GET http://localhost:8080/employees

Output.

[
    {
        "_id": "62f770c2740ed2290a62d7ad",
        "employee_id": 1,
        "first_name": "JOHN",
        "last_name": "DOE"
    },
    {
        "_id": "62f770c2740ed2290a62d7ae",
        "employee_id": 2,
        "first_name": "MARY",
        "last_name": "SMITH"
    },
    {
        "_id": "62f770c2740ed2290a62d7af",
       "employee_id": 3,
        "first_name": "DAVID",
        "last_name": "JACK"
    },
    {
        "_id": "62f77136ebf1445162cbd181",
        "employee_id": 4,
        "first_name": "HENRY",
        "last_name": "JACKSON"
    }
]

Retrieve a specific document:

$ curl -X GET http://localhost:8080/employees/4

Output.

[
    {
        "_id": "62f77136ebf1445162cbd181",
        "employee_id": 4,
        "first_name": "HENRY",
        "last_name": "JACKSON"
    }
]

Update a document (resouceId 4):

$ curl -X PUT http://127.0.0.1:8080/employees/4 -H 'Content-Type: application/json' -d '{"employee_id": 4, "first_name": " JACK", "last_name": "GEOFREY"}'

Output.

{
    "acknowledged": true,
    "modifiedCount": 1,
    "upsertedId": null,
    "upsertedCount": 0,
    "matchedCount": 1
}

Confirm the update command:

$ curl -X GET http://localhost:8080/employees/4

Output.

[
    {
        "_id": "62f770c2740ed2290a62d7ad",
        "employee_id": 4,
        "first_name": " JACK",
        "last_name": "GEOFREY"
    }
]

Delete a document:

$ curl -X DELETE http://localhost:8080/employees/2

Output.

{
    "acknowledged": true,
    "deletedCount": 1
}

Confirm the delete command:

$ curl -X GET http://localhost:8080/employees/2

Output.

[]

Conclusion

This guide implements the MongoDB document database using Node.js and Ubuntu 20.04 server. You've set up a database, created a central database module, and defined an entry point to the application. Then, you've run different tests using the Linux curl command to insert, find, update, and delete documents. Use the knowledge in this guide to build your next data-driven application when working with Node.js and MongoDB.

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Use MongoDB with Node.JS Print

Introduction

Prerequisites

1. Set a MongoDB Database

2. Create a `mongo_db_gateway` Class

3. Create an `index.js` File

4. Test the Application

Conclusion

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Knowledgebase

Categories

Categories

Support

Use MongoDB with Node.JS Print

Introduction

Prerequisites

1. Set a MongoDB Database

2. Create a mongo_db_gateway Class

3. Create an index.js File

4. Test the Application

Conclusion

Was this answer helpful?

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2. Create a `mongo_db_gateway` Class

3. Create an `index.js` File