2018-02-09

Instruction for creating a server app on Nodejs, Express and MongoDB

Based on simple example of app in which we can create, read, update and delete simple text documents

Component installation

The official site of nodejs (https://nodejs.org/) has detailed installation instructions

For centos:

1
2
3

$ curl —silent —location https://rpm.nodesource.com/setup_9.x | sudo bash -
$ sudo yum -y install nodejs
$ sudo yum install gcc-c++ make

For Ubuntu:

1
2
3

$ curl -sL https://deb.nodesource.com/setup_9.x | sudo -E bash -
$ sudo apt-get install -y nodejs
$ sudo apt-get install -y build-essential

Organize a folder for the project and execute a command for project initialization in it:

1	$ npm init

Answer the following questions

Project name
Project version
Description
Entry point
Testing team
Githhab’s repository
Project keywords
Author
License

Confirm and you’ll see file package.json, describing the project.

Now install the remaining components: Express and MongoDB (the latest version of the plugin does not work correctly with the database, so it’s better to install an earlier one):

1	$ npm install --save express mongodb@2.2.16

Also, for the convenience of handling url-encoded requests, install the body-parser:

1	$ npm install --save body-parser

And for the convenience of development, it is better to install Nodemon, which will restart the server every time when any files change:

1	$ npm install --save-dev nodemon

To attach Nodemon, you need to add the following to package.json:

{
  "name": "notable",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error^ no test specified\" && exit 1",
    "dev": "nodemon server.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.18.2",
    "express": "^4.16.2",
    "mongodb": "^2.2.16"
  },
  "devDependencies": {
    "nodemon": "^1.14.2"
  }
}

To be able to test app install Postman(https://www.getpostman.com/), which will simulate requests

Starting the server

Create file server.js in root directory, in which we write dependencies, specify the port and start listening:

const express        = require('express');
const MongoClient    = require('mongodb').MongoClient;
const bodyParser     = require('body-parser');
const app            = express();
const port = 8080;
app.listen(port, () => {
  console.log('We are live on ' + port);
});

Run the server:

1	npm run dev

In the terminal you can now see the message “We are live on port 8080”

Structure of project

For more convenient structuring of the project it is necessary to create an ‘app’ folder, in it we create the ‘routes’ folder, and in it - files ‘index.js’ and ‘note_routes.js’

So, the structure looks like this: in app/ routes - our route handlers, in the node_modules folder - the modules of our project, and server.js directly describes our server.

Connecting the DB

Add the ‘config’ directory to the project root, create a ‘db.js’. file in it.
In the file db.js write the following:

1
2
3

module.exports = {
  url : 'mongodb://localhost:27017/<yourDataBase>' 
};

In the file ‘server.js’ we add:

const express        = require('express');
const MongoClient    = require('mongodb').MongoClient;
const bodyParser     = require('body-parser');
const db = require(‘./config/db’);
const app            = express();
const port = 8080;
app.use(bodyParser.urlencoded({ extended: true }));
MongoClient.connect(db.url, (err, database) => {
  if (err) return console.log(err)
  require(‘./app/routes’)(app, database);
  app.listen(port, () => {
    console.log('We are live on ' + port);
  });
});

Creating a text document

In app/routes/note_routes.js we write:

1	module.exports = function(app, db) { };

In app/routes/index.js:

const noteRoutes = require('./note_routes');
 module.exports = function(app, db) {
  app.post('/notes', (req, res) => {
    const note = { text: req.body.body, title: req.body.title };
    db.collection('notes').insert(note, (err, result) => {
      if (err) { 
        res.send({ 'error': 'An error has occurred' }); 
      } else {
        res.send(result.ops[0]);
      }
    });
  });
};

Reading a text document

By analogy with app.post, we write another method:

app.get('/notes/:id', (req, res) => {
    const id = req.params.id;
    const details = { '_id': new ObjectID(id) };
    db.collection('notes').findOne(details, (err, item) => {
      if (err) {
        res.send({'error':'An error has occurred'});
      } else {
        res.send(item);
      } 
    });
  });

Deleting of text document

By analogy with app.post, we write another method:

app.delete('/notes/:id', (req, res) => {
    const id = req.params.id;
    const details = { '_id': new ObjectID(id) };
    db.collection('notes').remove(details, (err, item) => {
      if (err) {
        res.send({'error':'An error has occurred'});
      } else {
        res.send('Note ' + id + ' deleted!');
      } 
    });
  });

Updating of text document

By analogy with app.post, we write another method:

app.put ('/notes/:id', (req, res) => {
    const id = req.params.id;
    const details = { '_id': new ObjectID(id) };
    const note = { text: req.body.body, title: req.body.title };
    db.collection('notes').update(details, note, (err, result) => {
      if (err) {
          res.send({'error':'An error has occurred'});
      } else {
          res.send(note);
      } 
    });
  });

Testing with Postman

Postman allows specify the type of request (get, post, put, update), it’s address and port and add various parameters to the request body, for example, an empty POST request on the 8080 port.
Upon execution of the request, we see the server response.

alt-текст
Example of a POST request with a filled body: