Customer: Use Case (2: Implementing ExpressJS Service)

Prerequisites

1. Installed Node version of v20.10.0
2. Installed PostgreSQL version of 16
3. Database viewer, I use DBeaver

Creating customer table

1. Open DBeaver application
2. Click Database then choose New Database Connection assuming you haven't connect to PostgreSQL database.
3. Choose PostgreSQL. Then click Next.
4. I'm using the default connection settings so just click Finish.
5. You will see the newly connected PostgreSQL on the left side navigator.
6. Click the dropdown arrow until you can see this:
7. Click right at Databases. Choose Create New Database.
8. Fill the database name field with customer. Then click OK.
9. Click on database dropdown and now you will see your new database. If you did not see your new database, please follow this step.

Initialize express application

I'm assuming that you have already created project directories just like what I did in the first post.

1. Open a command prompt from express-service root directory.

2. Init a npm project by using command of:
   

   npm init
   

3. Install these dependencies:

   Basic dependencies

   ```
   npm install express dotenv cors body-parser
   ```
   

   Sequalize dependency

   ```
   npm install sequelize
   ```
   

   PostgreSQL dependency

   ```
   npm install pg pg-hstore
   ```
   

   UUID dependency

   ```
   npm install uuid
   ```
   

   My package.json dependencies looks like:
   

   "dependencies": {
       "body-parser": "^1.20.2",
       "cors": "^2.8.5",
       "dotenv": "^16.3.1",
       "express": "^4.18.2",
       "pg": "^8.11.3",
       "pg-hstore": "^2.3.4",
       "sequelize": "^6.35.1",
       "uuid": "^9.0.1"
     }
   

4. Create project directory skeleton that looks like this:
   

   express-service/
       ├── src/
       │   ├── configs/
       │   ├── controllers/
       │   ├── models/
       │   └── routes/
       ├── .env
       ├── index.js
       ├── package.json
       └── server.js
   

5. My .env file looks like below. Makesure that you have correct and working port and credentials.
   

   PORT=3001
   DB_HOST=localhost
   DB_PORT=5432
   DB_USERNAME=postgres
   DB_PASSWORD=password
   DB_NAME=customer
   

Creating configs

Inside configs directory, create a file named db.config.js the content will look like this:

require('dotenv').config();

module.exports = {
  HOST: process.env.DB_HOST,
  USER: process.env.DB_USERNAME,
  PASSWORD: process.env.DB_PASSWORD,
  DB: process.env.DB_NAME,
  dialect: "postgres",
  pool: {
    max: 5,
    min: 0,
    acquire: 30000,
    idle: 10000
  }
};

This is the configuration to connect our application to the database.

creating models

Now, let's move on to out models directory

1. Create a file called customer.model.js.
   

   module.exports = (sequalize, Sequalize) => {
     const Customer = sequalize.define("customer", {
       no: {
         type: Sequalize.UUID
       }, 
       nama: {
         type: Sequalize.STRING
       },
       alamat: {
         type: Sequalize.STRING
       },
       kota: {
         type: Sequalize.STRING
       }
     });
   
     return Customer;
   };
   

2. Create another file called index.js.
   

   const dbConfig = require("../configs/db.config");
   
   const Sequalize = require("sequelize");
   const sequalize = new Sequalize(dbConfig.DB, dbConfig.USER, dbConfig.PASSWORD, {
     host: dbConfig.HOST,
     dialect: 'postgres',
     operatorAliases: false,
   
     pool: {
       max: dbConfig.pool.max,
       min: dbConfig.pool.min,
       acquire: dbConfig.pool.acquire,
       idle: dbConfig.pool.idle
     }
   });
   
   const db = {};
   
   db.Sequalize = Sequalize;
   db.sequalize = sequalize;
   
   db.customer = require("./customer.model")(sequalize, Sequalize);
   
   module.exports = db;
   

Creating controllers

After configuring our model let's create the controller for customer by making a file called customer.controller.js.

const { v4: uuidv4 } = require('uuid');
const db = require("../models");
const model = require("../models");
const Customer = model.customer;
const Op = db.Sequalize.Op;

exports.create = (req, res) => {

  const customer = {
    no: uuidv4(),
    nama: req.body.nama,
    alamat: req.body.alamat,
    kota: req.body.kota
  };

  Customer.create(customer)
    .then((data) => {
      res.send(data);
    }).catch((err) => {
      res.status(500).send({
        message:
          err.message || "Some error occurred while creating the Customer."
      });
    });

};

exports.findAll = (req, res) => {

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

};

exports.findOne = (req, res) => {

  const id = req.params.id;

  Customer.findByPk(id)
    .then((data) => {
      res.send(data);
    }).catch((err) => {
      res.status(400).send({
        message:
          "Error retrieving Customer with id=" + id
      });
    });

};

exports.update = (req, res) => {

  const id = req.params.id;

  Customer.update(req.body, { where: { id: id } })
    .then((data) => {
      if (data[0] === 1) {
        res.send("Successfully updated Customer with id " + id);
      } else {
        res.send("Cannot update Customer with id " + id);
      }
    }).catch((err) => {
      res.status(500).send({
        message: "Error updating Customer with id=" + id
      });
    });

};

exports.delete = (req, res) => {

  const id = req.params.id;

  Customer.destroy({ where: { id: id } })
    .then((data) => {
      if (data === 1) {
        res.send("Successfully deleted Customer with id " + id);
      } else {
        res.send("Cannot delete Customer with id " + id);
      }
    }).catch((err) => {
      res.status(500).send({
        message: "Error deleting Customer with id=" + id
      });
    });

};

Creating routes

Last, we need to create our route in customer.route.js inside route directory.

module.exports = app => {
  const customers = require("../controllers/customer.controller");

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

  router.post("/", customers.create);

  router.get("/", customers.findAll);

  router.get("/:id", customers.findOne);

  router.put("/:id", customers.update);

  router.delete("/:id", customers.delete);

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

Configuring server

In server.js file which located in root directory, we will configuring all needed dependency and connect our application to database like this:

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

require('dotenv').config();

function startServer() {
  const app = express();

  app.use(cors());

  app.use(express.json());

  app.use(express.urlencoded({ extended: true }));

  const db = require("./src/models");

  db.sequalize.sync()
    .then(() => {
      console.log("Synced db.");
    }).catch((err) => {
      console.log("Failed to sync db: " + err.message);
    });

    require("./src/routes/customer.routes")(app);

  const PORT = process.env.PORT;
  app.listen(PORT, () => {
    console.log(`Server running on port ${PORT}`);
  });
};

module.exports = { start: startServer };

Configure index.js

Since most functionalities all already handled by server.js, in index.js we just have to call it like this:

const server = require('./server');

server.start();

Running application

1. Back to express-service root directory, open command prompt directed to the directory.
2. Run node index.js
3. If it running correctly you will see this log:
4. Test your API endpoints using Postman or Thunder Client.