Overview

Today I will write something different in this article. Most of my articles are based on Go and Java. Now I will try to write something with Javascript, a must known programming language for most developers. More precise, I will write a simple CRUD service with NodeJS and Neo4j as a persistence data store.

How to install NodeJS, NVM and Neo4j are beyond the scope of this article.

ExpressJS

ExpressJS is a server-side web framework for NodeJS. It builds on the top of NodeJS. One of the important strength of ExpressJS is, it makes routing very easy. Furthermore, it is the most popular web framework in NodeJS world.

Neo4j

Neo4j is a graph database management system developed by Neo4j, Inc. Described by its developers as an ACID-compliant transactional database with native graph storage and processing¹. It supports Cypher Query Language (CQL) to manipulate data in graph database. For this article, I will use docker to run neo4j instance.

docker run -p 7474:7474 -p 7687:7687 volume=$HOME/neo4j/data:/data neo4j

1	docker run -p 7474:7474 -p 7687:7687 volume=$HOME/neo4j/data:/data neo4j

Use Case

For this use case, I will create a service that can insert, update, list and delete a company data. The data will be stored as a graph inside Neo4j.

Step 1: Create Express App

I will create an express app with name expressjs-neo4j. First, I need to install express-generator in order to install a wizard to create project setup.

npm install express-generator -g

1	npm install express-generator -g

We can create a directory outline just by typing:

express --view=ejs expressjs-neo4j

1	express --view=ejs expressjs-neo4j

It will generate files and folders that are necessary for express to run. Then type

cd expressjs-neo4j && npm install
npm start

1 2	cd expressjs-neo4j && npm install npm start

Open a browser http://localhost:3000 to validate that your express is up and running.

Step 2: Installing Modules

There are some modules that are necessary in order to make our service run based on its functionalities. For example, neo4j-driver module for database driver. There are many more modules to be installed.

npm install morgan body-parser cors neo4j-driver method-override config.json lodash swagger-node-express swagger-jsdoc swagger-ui-express passport passport-jwt jsonwebtoken --save
npm install mocha chai chai-http --save-dev

1 2	npm install morgan body-parser cors neo4j-driver method-override config.json lodash swagger-node-express swagger-jsdoc swagger-ui-express passport passport-jwt jsonwebtoken --save npm install mocha chai chai-http --save-dev

Step 3: Setup Configuration

Setup the configuration file to configure database connection parameters and several initial values.

// file: config/config.js
{
  "development": {
    "username": "neo4j",
    "password": "password",
    "neo4j": "bolt://localhost:7687",
    "base_url": "http://localhost:3000",
    "api_path": "/api/v0",
    "jwtKey": "SkyIsFallingDown"
  }
}

// file: config/config.js

{

"development": {

"username": "neo4j",

"password": "password",

"neo4j": "bolt://localhost:7687",

"base_url": "http://localhost:3000",

"api_path": "/api/v0",

"jwtKey": "SkyIsFallingDown"

}

There are several steps needs to be configured inside app.js. For instance, to enable authorization by using PassportJS, compress payload and expose swagger endpoint. See the source code for more details.

Step 4: Database Connection Utility

For getting database session easier, I will create a utility file for database connectivity.

// file: neo4j/dbUtils.js

var env = process.env.NODE_ENV || 'development';
var config = require('../config/config')[env];
var neo4j = require('neo4j-driver').v1;

var driver = neo4j.driver(config.neo4j, neo4j.auth.basic(config.username, config.password));


exports.getSession = function (context) {
  if (context.neo4jSession) {
    return context.neo4jSession;
  } else {
    context.neo4jSession = driver.session();
    return context.neo4jSession;
  }
};

// and the rest

// file: neo4j/dbUtils.js

var env = process.env.NODE_ENV || 'development';

var config = require('../config/config')[env];

var neo4j = require('neo4j-driver').v1;

var driver = neo4j.driver(config.neo4j, neo4j.auth.basic(config.username, config.password));

exports.getSession = function (context) {

if (context.neo4jSession) {

return context.neo4jSession;

} else {

context.neo4jSession = driver.session();

return context.neo4jSession;

}

};

// and the rest

Step 5: Model

Now create a model as a persistence layer to graph database.

// file: models/company.js
var Company = require('../models/neo4j/company')

var create = function (session, company) {
  let query = 'CREATE (c:Company{id: {id}, companyName: {companyName}, createdDate: {createdDate}, updatedDate: {updatedDate}}) RETURN c'
  var writexResultPromise = session.writeTransaction(function (transaction) {
    // used transaction will be committed automatically, no need for explicit commit/rollback
    var result = transaction.run(query, {
      id: company.id,
      companyName: company.companyName,
      createdDate: company.createdDate,
      updatedDate: company.updatedDate
    })
    return result
  })

  return writexResultPromise.then(_returnBySingleId).catch(_handlePayloadValidation)
}

// and the rest CRUD operations

// file: models/company.js

var Company = require('../models/neo4j/company')

var create = function (session, company) {

let query = 'CREATE (c:Company{id: {id}, companyName: {companyName}, createdDate: {createdDate}, updatedDate: {updatedDate}}) RETURN c'

var writexResultPromise = session.writeTransaction(function (transaction) {

// used transaction will be committed automatically, no need for explicit commit/rollback

var result = transaction.run(query, {

id: company.id,

companyName: company.companyName,

createdDate: company.createdDate,

updatedDate: company.updatedDate

})

return result

})

return writexResultPromise.then(_returnBySingleId).catch(_handlePayloadValidation)

}

// and the rest CRUD operations

The other one to extract data from query results.

// file: models/neo4j/company.js
var _ = require('lodash');

var Company = module.exports = function (_node) {
  _.extend(this, _node.properties);
  if(this.createdDate) {
    this.createdDate = new Date(this.createdDate.toString());
  }
  if(this.updatedDate) {
    this.updatedDate = new Date(this.updatedDate.toString());
  }
};

// file: models/neo4j/company.js

var _ = require('lodash');

var Company = module.exports = function (_node) {

_.extend(this, _node.properties);

if(this.createdDate) {

this.createdDate = new Date(this.createdDate.toString());

}

if(this.updatedDate) {

this.updatedDate = new Date(this.updatedDate.toString());

}

};

Note: I extend the date property because neo4j date property is a little bit different. See how to get date in the neo4j/dbUtils.js for more details.

Step 6: Routes

Create a function to route service endpoint.

// file: routes/companies.js
var Company = require('../models/company')
var writeResponse = require('../helpers/response').writeResponse
var dbUtils = require('../neo4j/dbUtils')
var uuidv1 = require('uuid/v1')

let logging = function (log, message, info) {
  if (process.env.NODE_ENV !== 'test') {
    log.info(info, message)
  }
}

/**
* @swagger
* /api/v0/companies:
*   post:
*     tags:
*     - company
*     description: ''
*     summary: Add a new company
*     produces:
*       - application/json
*     parameters:
*       - in: body
*         name: body
*         description: Company object that needs to be added to the system. ID will be replaced by system.
*         required: true
*         schema:
*           $ref: '#/definitions/Company'
*     security:
*       - Bearer: []
*       - api_key: []
*     responses:
*       200:
*         description: Company created
*       401:
*         description: Unauthorized. Need JWT.
*       409:
*         description: Invalid payload
*/
exports.create = function (req, res, next) {
  let currentDate = dbUtils.getCurrentDate()
  req.body.id = uuidv1()
  req.body.createdDate = currentDate
  req.body.updatedDate = currentDate
  logging(req.log, 'Create company',
    { user: req.user, id: req.body.id, companyName: req.body.companyName })

  Company.create(dbUtils.getSession(req), req.body)
    .then(response => writeResponse(res, response))
    .catch(next)
}

// and the rest CRUD functions

// file: routes/companies.js

var Company = require('../models/company')

var writeResponse = require('../helpers/response').writeResponse

var dbUtils = require('../neo4j/dbUtils')

var uuidv1 = require('uuid/v1')

let logging = function (log, message, info) {

if (process.env.NODE_ENV !== 'test') {

log.info(info, message)

}

/**

* @swagger

* /api/v0/companies:

* post:

* tags:

* - company

* description: ''

* summary: Add a new company

* produces:

* - application/json

* parameters:

* - in: body

* name: body

* description: Company object that needs to be added to the system. ID will be replaced by system.

* required: true

* schema:

* $ref: '#/definitions/Company'

* security:

* - Bearer: []

* - api_key: []

* responses:

* 200:

* description: Company created

* 401:

* description: Unauthorized. Need JWT.

* 409:

* description: Invalid payload

exports.create = function (req, res, next) {

let currentDate = dbUtils.getCurrentDate()

req.body.id = uuidv1()

req.body.createdDate = currentDate

req.body.updatedDate = currentDate

logging(req.log, 'Create company',

{ user: req.user, id: req.body.id, companyName: req.body.companyName })

Company.create(dbUtils.getSession(req), req.body)

.then(response => writeResponse(res, response))

.catch(next)

}

// and the rest CRUD functions

Note: I embed the swagger-code-gen to generate documentation in swagger-ui.

And add the router to app.js

// file: app.js

// api routes
api.get('/companies', routes.companies.list)
api.post('/companies', routes.companies.create)
api.put('/companies', routes.companies.update)
api.get('/companies/:companyId', routes.companies.getCompanyById)
api.delete('/companies/:companyId', routes.companies.remove)

// file: app.js

// api routes

api.get('/companies', routes.companies.list)

api.post('/companies', routes.companies.create)

api.put('/companies', routes.companies.update)

api.get('/companies/:companyId', routes.companies.getCompanyById)

api.delete('/companies/:companyId', routes.companies.remove)

Step 7: Execute and Run

Since we activate the authorization, so we need to pass the JWT in the request header.

// execute
npm run

// test via curl
curl -X POST http://localhost:3000/api/v0/companies \
     -H 'Authorization: Bearer [your jwt token]' \
     -H 'Content-type: application/json' \
     -d '{"companyName": "XYZ" }'

// reponse:
{
  "createdDate": "2018-08-28T11:07:41.948Z",
  "id": "e8de19e0-aa77-11e8-b7a2-011b2eec63e3",
  "updatedDate": "2018-08-28T11:07:41.948Z",
  "companyName": "XYZ"
}

// execute

npm run

// test via curl

curl -X POST http://localhost:3000/api/v0/companies \

-H 'Authorization: Bearer [your jwt token]' \

-H 'Content-type: application/json' \

-d '{"companyName": "XYZ" }'

// reponse:

{

"createdDate": "2018-08-28T11:07:41.948Z",

"id": "e8de19e0-aa77-11e8-b7a2-011b2eec63e3",

"updatedDate": "2018-08-28T11:07:41.948Z",

"companyName": "XYZ"

}

One more interesting information, go to your browser and type http://localhost:3000/api-docs. You will get the list of your swagger documentation.

Sample Code

That’s from me now. You can see complete source code, including how to run testing using karma and chai, on my github.

Author: ru rocker

I have been a professional software developer since 2004. Java, Python, NodeJS, and Go-lang are my favorite programming languages. I also have an interest in DevOps. I hold professional certifications: SCJP, SCWCD, PSM 1, AWS Solution Architect Associate, and AWS Solution Architect Professional. View all posts by ru rocker

2 thoughts on “How to Make a Simple CRUD Example using ExpressJS and Neo4j”

tony says:

March 29, 2019 at 4:55 am

Great example! Can you elaborate on creating/using the JWT token? Thanks!

Omar says:

December 30, 2019 at 4:18 am

I would like to know more about neo4j and its use… you can write me to my email. Grettings