Node.js Express & PostgreSQL: CRUD Rest APIs example with Sequelize

Node.js Rest CRUD API overview

We will build Rest Apis that can create, retrieve, update, delete and find Tutorials by title.

First, we start with an Express web server. Next, we add configuration for PostgreSQL database, create Tutorial model with Sequelize, write the controller. Then we define routes for handling all CRUD operations (including custom finder).

The following table shows overview of the Rest APIs that will be exported:

Methods

Urls

Actions

GET

api/tutorials

get all Tutorials

GET

api/tutorials/:id

get Tutorial by id

POST

api/tutorials

add new Tutorial

PUT

api/tutorials/:id

update Tutorial by id

DELETE

api/tutorials/:id

remove Tutorial by id

DELETE

api/tutorials

remove all Tutorials

GET

api/tutorials/published

find all published Tutorials

GET

api/tutorials?title=[kw]

find all Tutorials which title contains 'kw'

Finally, we’re gonna test the Rest Apis using Postman.

This is our project structure:

Create Node.js App

First, we create a folder:

$ mkdir nodejs-express-sequelize-postgresql
$ cd nodejs-express-sequelize-postgresql

Next, we initialize the Node.js App with a package.json file:

npm init

name: (nodejs-express-sequelize-postgresql) 
version: (1.0.0) 
description: Node.js Rest Apis with Express, Sequelize & PostgreSQL.
entry point: (index.js) server.js
test command: 
git repository: 
keywords: nodejs, express, sequelize, postgresql, rest, api
author: bezkoder
license: (ISC)

Is this ok? (yes) yes

We need to install necessary modules: express, sequelize, pg, pg-hstore and body-parser. Run the command:

npm install express sequelize pg pg-hstore body-parser cors --save

*pg for PostgreSQL and pg-hstore for converting data into the PostgreSQL hstore format.

The package.json file should look like this:

{
  "name": "nodejs-express-sequelize-postgresql",
  "version": "1.0.0",
  "description": "Node.js Rest Apis with Express, Sequelize & M",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [
    "nodejs",
    "express",
    "sequelize",
    "rest",
    "api",
    "postgresql"
  ],
  "author": "bezkoder",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.19.0",
    "cors": "^2.8.5",
    "express": "^4.17.1",
    "pg": "^7.17.1",
    "pg-hstore": "^2.3.3",
    "sequelize": "^5.21.3"
  }
}

Setup Express web server

In the root folder, let’s create a new server.js file:

const express = require("express");
const bodyParser = require("body-parser");
const cors = require("cors");

const app = express();

var corsOptions = {
  origin: "http://localhost:8081"
};

app.use(cors(corsOptions));

// parse requests of content-type - application/json
app.use(bodyParser.json());

// parse requests of content-type - application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: true }));

// simple route
app.get("/", (req, res) => {
  res.json({ message: "Welcome to bezkoder application." });
});

// set port, listen for requests
const PORT = process.env.PORT || 8080;
app.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}.`);
});

What we do are: – import express, body-parser and cors modules:

Express is for building the Rest apis
body-parser helps to parse the request and create the req.body object
cors provides Express middleware to enable CORS with various options.

– create an Express app, then add body-parser and cors middlewares using app.use() method. Notice that we set origin: http://localhost:8081. – define a GET route which is simple for test. – listen on port 8080 for incoming requests.

Now let’s run the app with command: node server.js. Open your browser with url http://localhost:8080/, you will see:

Yeah, the first step is done. We’re gonna work with Sequelize in the next section.

Configure PostgreSQL database & Sequelize

In the app folder, we create a separate config folder for configuration with db.config.js file like this:

module.exports = {
  HOST: "localhost",
  USER: "postgres",
  PASSWORD: "123",
  DB: "testdb",
  dialect: "postgres",
  pool: {
    max: 5,
    min: 0,
    acquire: 30000,
    idle: 10000
  }
};

First five parameters are for PostgreSQL connection. pool is optional, it will be used for Sequelize connection pool configuration:

max: maximum number of connection in pool
min: minimum number of connection in pool
idle: maximum time, in milliseconds, that a connection can be idle before being released
acquire: maximum time, in milliseconds, that pool will try to get connection before throwing error

For more details, please visit API Reference for the Sequelize constructor.

Initialize Sequelize

We’re gonna initialize Sequelize in app/models folder that will contain model in the next step.

Now create app/models/index.js with the following code:

const dbConfig = require("../config/db.config.js");

const Sequelize = require("sequelize");
const sequelize = new Sequelize(dbConfig.DB, dbConfig.USER, dbConfig.PASSWORD, {
  host: dbConfig.HOST,
  dialect: dbConfig.dialect,
  operatorsAliases: false,

  pool: {
    max: dbConfig.pool.max,
    min: dbConfig.pool.min,
    acquire: dbConfig.pool.acquire,
    idle: dbConfig.pool.idle
  }
});

const db = {};

db.Sequelize = Sequelize;
db.sequelize = sequelize;

db.tutorials = require("./tutorial.model.js")(sequelize, Sequelize);

module.exports = db;

Don’t forget to call sync() method in server.js:

...
const app = express();
app.use(...);

const db = require("./app/models");
db.sequelize.sync();

...

In development, you may need to drop existing tables and re-sync database. Just use force: true as following code:


db.sequelize.sync({ force: true }).then(() => {
  console.log("Drop and re-sync db.");
});

Define the Sequelize Model

In models folder, create tutorial.model.js file like this:

module.exports = (sequelize, Sequelize) => {
  const Tutorial = sequelize.define("tutorial", {
    title: {
      type: Sequelize.STRING
    },
    description: {
      type: Sequelize.STRING
    },
    published: {
      type: Sequelize.BOOLEAN
    }
  });

  return Tutorial;
};

This Sequelize Model represents tutorials table in PostgreSQL database. These columns will be generated automatically: id, title, description, published, createdAt, updatedAt.

After initializing Sequelize, we don’t need to write CRUD functions, Sequelize supports all of them:

create a new Tutorial: create(object)
find a Tutorial by id: findByPk(id)
get all Tutorials: findAll()
update a Tutorial by id: update(data, where: { id: id })
remove a Tutorial: destroy(where: { id: id })
remove all Tutorials: destroy(where: {})
find all Tutorials by title: findAll({ where: { title: ... } })

These functions will be used in our Controller.

We can improve the example by adding Comments for each Tutorial. It is the One-to-Many Relationship and I write a tutorial for this at: Node.js Sequelize Associations: One-to-Many example

Or you can add Tags for each Tutorial and add Tutorials to Tag (Many-to-Many Relationship): Node.js Sequelize Associations: Many-to-Many example

Create the Controller

Inside app/controllers folder, let’s create tutorial.controller.js with these CRUD functions:

create
findAll
findOne
update
delete
deleteAll
findAllPublished

const db = require("../models");
const Tutorial = db.tutorials;
const Op = db.Sequelize.Op;

// Create and Save a new Tutorial
exports.create = (req, res) => {
  
};

// Retrieve all Tutorials from the database.
exports.findAll = (req, res) => {
  
};

// Find a single Tutorial with an id
exports.findOne = (req, res) => {
  
};

// Update a Tutorial by the id in the request
exports.update = (req, res) => {
  
};

// Delete a Tutorial with the specified id in the request
exports.delete = (req, res) => {
  
};

// Delete all Tutorials from the database.
exports.deleteAll = (req, res) => {
  
};

// Find all published Tutorials
exports.findAllPublished = (req, res) => {
  
};

Let’s implement these functions.

Create a new object

Create and Save a new Tutorial:

exports.create = (req, res) => {
  // Validate request
  if (!req.body.title) {
    res.status(400).send({
      message: "Content can not be empty!"
    });
    return;
  }

  // Create a Tutorial
  const tutorial = {
    title: req.body.title,
    description: req.body.description,
    published: req.body.published ? req.body.published : false
  };

  // Save Tutorial in the database
  Tutorial.create(tutorial)
    .then(data => {
      res.send(data);
    })
    .catch(err => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while creating the Tutorial."
      });
    });
};

Retrieve objects (with condition)

Retrieve all Tutorials/ find by title from the database:

exports.findAll = (req, res) => {
  const title = req.query.title;
  var condition = title ? { title: { [Op.iLike]: `%${title}%` } } : null;

  Tutorial.findAll({ where: condition })
    .then(data => {
      res.send(data);
    })
    .catch(err => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while retrieving tutorials."
      });
    });
};

We use req.query.title to get query string from the Request and consider it as condition for findAll() method.

Retrieve a single object

Find a single Tutorial with an id:

exports.findOne = (req, res) => {
  const id = req.params.id;

  Tutorial.findByPk(id)
    .then(data => {
      res.send(data);
    })
    .catch(err => {
      res.status(500).send({
        message: "Error retrieving Tutorial with id=" + id
      });
    });
};

Update an object

Update a Tutorial identified by the id in the request:

exports.update = (req, res) => {
  const id = req.params.id;

  Tutorial.update(req.body, {
    where: { id: id }
  })
    .then(num => {
      if (num == 1) {
        res.send({
          message: "Tutorial was updated successfully."
        });
      } else {
        res.send({
          message: `Cannot update Tutorial with id=${id}. Maybe Tutorial was not found or req.body is empty!`
        });
      }
    })
    .catch(err => {
      res.status(500).send({
        message: "Error updating Tutorial with id=" + id
      });
    });
};

Delete an object

Delete a Tutorial with the specified id:

exports.delete = (req, res) => {
  const id = req.params.id;

  Tutorial.destroy({
    where: { id: id }
  })
    .then(num => {
      if (num == 1) {
        res.send({
          message: "Tutorial was deleted successfully!"
        });
      } else {
        res.send({
          message: `Cannot delete Tutorial with id=${id}. Maybe Tutorial was not found!`
        });
      }
    })
    .catch(err => {
      res.status(500).send({
        message: "Could not delete Tutorial with id=" + id
      });
    });
};

Delete all objects

Delete all Tutorials from the database:

exports.deleteAll = (req, res) => {
  Tutorial.destroy({
    where: {},
    truncate: false
  })
    .then(nums => {
      res.send({ message: `${nums} Tutorials were deleted successfully!` });
    })
    .catch(err => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while removing all tutorials."
      });
    });
};

Find all objects by condition

Find all Tutorials with published = true:

exports.findAllPublished = (req, res) => {
  Tutorial.findAll({ where: { published: true } })
    .then(data => {
      res.send(data);
    })
    .catch(err => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while retrieving tutorials."
      });
    });
};

Define Routes

When a client sends request for an endpoint using HTTP request (GET, POST, PUT, DELETE), we need to determine how the server will reponse by setting up the routes.

These are our routes:

/api/tutorials: GET, POST, DELETE
/api/tutorials/:id: GET, PUT, DELETE
/api/tutorials/published: GET

Create a turorial.routes.js inside app/routes folder with content like this:

module.exports = app => {
  const tutorials = require("../controllers/tutorial.controller.js");

  var router = require("express").Router();

  // Create a new Tutorial
  router.post("/", tutorials.create);

  // Retrieve all Tutorials
  router.get("/", tutorials.findAll);

  // Retrieve all published Tutorials
  router.get("/published", tutorials.findAllPublished);

  // Retrieve a single Tutorial with id
  router.get("/:id", tutorials.findOne);

  // Update a Tutorial with id
  router.put("/:id", tutorials.update);

  // Delete a Tutorial with id
  router.delete("/:id", tutorials.delete);

  // Create a new Tutorial
  router.delete("/", tutorials.deleteAll);

  app.use('/api/tutorials', router);
};

You can see that we use a controller from /controllers/tutorial.controller.js.

We also need to include routes in server.js (right before app.listen()):

...

require("./app/routes/turorial.routes")(app);

// set port, listen for requests
const PORT = ...;
app.listen(...);

Test the APIs

Run our Node.js application with command: node server.js.

Using Postman, we’re gonna test all the Apis above.

Create a new Tutorial using POST /tutorials Api

node-js-express-sequelize-postgresql-crud-create

After creating some new Tutorials, you can check PostgreSQL table:

testdb=# select * from tutorials;
 id |    title    |    description    | published |         createdAt          |         updatedAt
----+-------------+-------------------+-----------+----------------------------+----------------------------
  1 | Node Tut #1 | Tut#1 Description | f         | 2020-01-29 10:42:57.121+07 | 2020-01-29 10:42:57.121+07
  2 | Node Tut #2 | Tut#2 Description | f         | 2020-01-29 10:43:05.131+07 | 2020-01-29 10:43:05.131+07
  3 | Node Tut #3 | Tut#3 Description | f         | 2020-01-29 10:43:48.028+07 | 2020-01-29 10:43:48.028+07
  4 | Js Tut #4   | Tut#4 Desc        | f         | 2020-01-29 10:45:40.016+07 | 2020-01-29 10:45:40.016+07
  5 | Js Tut #5   | Tut#5 Desc        | f         | 2020-01-29 10:45:44.289+07 | 2020-01-29 10:45:44.289+07

Retrieve all Tutorials using GET /tutorials Api
Retrieve a single Tutorial by id using GET /tutorials/:id Api

Update a Tutorial using PUT /tutorials/:id Api

node-js-express-sequelize-postgresql-crud-update

Check tutorials table after some rows were updated:

testdb=# select * from tutorials;
 id |     title      |    description    | published |         createdAt          |         updatedAt
----+----------------+-------------------+-----------+----------------------------+----------------------------
  1 | Node Tut #1    | Tut#1 Description | f         | 2020-01-29 10:42:57.121+07 | 2020-01-29 10:42:57.121+07
  3 | Node Tut #3    | Tut#3 Description | f         | 2020-01-29 10:43:48.028+07 | 2020-01-29 10:43:48.028+07
  2 | Node Js Tut #2 | Tut#2 Description | t         | 2020-01-29 10:43:05.131+07 | 2020-01-29 10:51:55.235+07
  4 | Js Tut #4      | Tut#4 Desc        | t         | 2020-01-29 10:45:40.016+07 | 2020-01-29 10:54:17.468+07
  5 | Js Tut #5      | Tut#5 Desc        | t         | 2020-01-29 10:45:44.289+07 | 2020-01-29 10:54:20.544+07

Find all Tutorials which title contains ‘js’: GET /tutorials?title=js
Find all published Tutorials using GET /tutorials/published Api

Delete a Tutorial using DELETE /tutorials/:id Api

node-js-express-sequelize-postgresql-crud-delete

Tutorial with id=4 was removed from tutorials table:

testdb=# select * from tutorials;
 id |     title      |    description    | published |         createdAt          |         updatedAt
----+----------------+-------------------+-----------+----------------------------+----------------------------
  1 | Node Tut #1    | Tut#1 Description | f         | 2020-01-29 10:42:57.121+07 | 2020-01-29 10:42:57.121+07
  3 | Node Tut #3    | Tut#3 Description | f         | 2020-01-29 10:43:48.028+07 | 2020-01-29 10:43:48.028+07
  2 | Node Js Tut #2 | Tut#2 Description | t         | 2020-01-29 10:43:05.131+07 | 2020-01-29 10:51:55.235+07
  5 | Js Tut #5      | Tut#5 Desc        | t         | 2020-01-29 10:45:44.289+07 | 2020-01-29 10:54:20.544+07

Delete all Tutorials using DELETE /tutorials Api

node-js-express-sequelize-postgresql-crud-delete-all

Now there are no rows in tutorials table:

testdb=# select * from tutorials;
 id | title | description | published | createdAt | updatedAt
----+-------+-------------+-----------+-----------+-----------

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