Epoch 3: Build the Product Service (ExpressJS)

Objectives

• Build a separate microservice for managing product data.
• Connect the service to its own MongoDB database.
• Implement CRUD operations for products using RESTful API principles.
• Apply input validation and error handling.
• Maintain a clean and modular folder structure.

1. Microservice Overview

• Service Name: product-service
• Responsibility: Manage product catalog including create, update, view, and delete operations.
• Technology Stack: Node.js, ExpressJS, MongoDB, Mongoose

2. Structure architechture

product-service/
├── controllers/
│   └── product.controller.js
├── models/
│   └── product.model.js
├── routes/
│   └── product.routes.js
├── middlewares/
│   └── errorHandler.js
├── .env
├── server.js
├── package.json

2.1. Project Setup

• Step 1: Initialize the Project

  mkdir product-service
  cd product-service
  npm init -y
  

• Step 2: Install Dependencies

  npm install express mongoose dotenv
  

• Step 3: Project Structure: Create the following folders and files:

  mkdir controllers models routes middlewares
  touch server.js .env
  

2.2. Mongoose Product Schema

// models/product.model.js
const mongoose = require('mongoose');

const productSchema = new mongoose.Schema({
  name: { type: String, required: true },
  description: String,
  price: { type: Number, required: true, min: 0 },
  stock: { type: Number, default: 0 },
  category: String,
  createdAt: { type: Date, default: Date.now }
});

module.exports = mongoose.model('Product', productSchema);

2.3. Product Controller

• controllers/product.controller.js ```js const Product = require(‘../models/product.model’);

exports.createProduct = async (req, res) => { try { const product = await Product.create(req.body); res.status(201).json(product); } catch (err) { res.status(400).json({ error: ‘Failed to create product.’ }); } };

exports.getAllProducts = async (req, res) => { const products = await Product.find(); res.json(products); };

exports.getProductById = async (req, res) => { const product = await Product.findById(req.params.id); if (!product) return res.status(404).json({ error: ‘Product not found’ }); res.json(product); };

exports.updateProduct = async (req, res) => { const product = await Product.findByIdAndUpdate(req.params.id, req.body, { new: true }); if (!product) return res.status(404).json({ error: ‘Product not found’ }); res.json(product); };

exports.deleteProduct = async (req, res) => { const product = await Product.findByIdAndDelete(req.params.id); if (!product) return res.status(404).json({ error: ‘Product not found’ }); res.json({ message: ‘Product deleted successfully’ }); };

### 2.4. Routes
- routes/product.routes.js
```js
const express = require('express');
const router = express.Router();
const {
  createProduct,
  getAllProducts,
  getProductById,
  updateProduct,
  deleteProduct
} = require('../controllers/product.controller');

router.post('/', createProduct);
router.get('/', getAllProducts);
router.get('/:id', getProductById);
router.put('/:id', updateProduct);
router.delete('/:id', deleteProduct);

module.exports = router;

2.5. Server Setup

• server.js ```js // server.js const express = require(‘express’); const mongoose = require(‘mongoose’); require(‘dotenv’).config();

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

// Routes app.use(‘/api/products’, require(‘./routes/product.routes’));

mongoose.connect(process.env.MONGO_URI) .then(() => app.listen(process.env.PORT, () => { console.log(Product service running on port ${process.env.PORT}); })) .catch(err => console.error(err));

### 2.6. Environment Variables
Create a .env file in the root directory:

PORT=4002 MONGO_URI=mongodb://localhost:27017/product-service ```

3. Testing with Postman

• Example Request Payload { “name”: “iPhone 15”, “description”: “Latest Apple smartphone”, “price”: 999, “stock”: 10, “category”: “Electronics” }

Method	Endpoint	Description	Request Body
POST	/api/products	Create new product	has Payload
GET	/api/products	Get all products	-
GET	/api/products/:id	Get product by ID	-
PUT	/api/products/:id	Update product	has Payload
DELETE	/api/products/:id	Delete product	-