Neil Haddley - Developer & Technical Consultant

REST

Neil Haddley • February 6, 2021

Creating a REST API Service using Node and Express

HTTP Methods/Verbs

Hypertext Transfer Protocol (HTTP) defines a set of request methods that a client application will use to ask an HTTP server to do something. HTTP request methods are often called verbs. HTTP verbs include:

Get A client application will use a Get method to retrieve something from an HTTP server.

Post A client application will use a Post method to send something to an HTTP server.

Put A client application will use a Put method to request that something managed by an HTTP server is updated.Delete A client application will use the Delete method to request that something managed by an HTTP server is thrown away.

API Routes

Routing determines how an HTTP server will respond to a client request. The client application will specify a path and an HTTP verb.

Route parameters are passed as part of the URL provided to the HTTP server.

https://localhost/books

request details of all books

https://localhost/books/1788395549

request details of the book with ISBN Number 1788395549

Route handlers and Response methods

Route handlers are functions that execute on the HTTP server when a request is received from the client application.

Response methods are used to send something back to the client application. Response methods include:

send() Sends a response to the client.

sendFile() Sends a file to the client.

redirect() Redirects the request.

json() Sends a JavaScript object to the client.

status() Sets the HTTP status code

Using Node.js and Express

npm can be used to initialise a REST API project.

$ mkdir books

$ cd books

$ npm init

$ npm i express

The package.json file

The package.json file generated by npm should be updated to:

The index.js file

The index.js file generated by npm should be updated to:

The Dockerfile

Visual Studio Code is able to add a Dockerfile to a Node.js project automagically.

Open the Command Palette (⇧⌘P) and use the "Docker: Add Docker Files to Workspace..." command:

FROM node:12.18-alpine

ENV NODE_ENV=production

WORKDIR /usr/src/app

COPY ["package.json", "package-lock.json", "npm-shrinkwrap.json", "./"]

RUN npm install --production --silent && mv node_modules ../

COPY . .

EXPOSE 5000

CMD ["npm", "start"]

REST API Service

/books route

/books/id route with a valid id

/books/id with an invalid id

Example route handlers

JAVASCRIPT

1app.get('/books', (request, response) => {
2    response.json(books);
3});
4
5app.get('/books/:id', (request, response) => {
6    const isbnId = Number(request.params.id);
7    const found = books.find((book) => book.id === isbnId);
8
9    if (!found) {
10        response.status(404).send('Book Not Found');
11    } else {
12        response.json(found);
13    }
14});

package.json

JAVASCRIPT

1{
2  "name": "books",
3  "version": "1.0.0",
4  "description": "",
5  "main": "index.js",
6  "scripts": {
7    "start": "node index.js"
8  },
9  "author": "",
10  "license": "ISC",
11  "dependencies": {
12    "express": "^4.17.1"
13  }
14}

index.js

JAVASCRIPT

1const express = require('express');
2const app = express();
3let books = [
4    {
5        "id": 1788395549,
6        "title": "Learning Node.js Development",
7    },
8    {
9        "id": 1788620216,
10        "title": "Hands-On Microservices with Node.js",
11    }
12];
13
14app.get('/books', (request, response) => {
15    response.json(books);
16});
17
18app.get('/books/:id', (request, response) => {
19    const isbnId = Number(request.params.id);
20    const found = books.find((book) => book.id === isbnId);
21
22    if (!found) {
23        response.status(404).send('Book Not Found');
24    } else {
25        response.json(found);
26    }
27});
28
29
30app.listen(5000, () => console.log('server running'));