Building REST APIs

Beginner Lesson 1 of 1

Building REST APIs

Learn to design and implement professional REST APIs.

REST Principles

Stateless - Each request contains all needed information
Resource-based - URLs represent resources, not actions
HTTP Methods - Use GET, POST, PUT, PATCH, DELETE appropriately
Status Codes - Return meaningful HTTP status codes

Express.js REST API

const express = require('express');
const app = express();

app.use(express.json());

// In-memory data store
let users = [
  { id: 1, name: 'Alice', email: 'alice@example.com' },
  { id: 2, name: 'Bob', email: 'bob@example.com' },
];

// GET all users
app.get('/api/users', (req, res) => {
  res.json(users);
});

// GET single user
app.get('/api/users/:id', (req, res) => {
  const user = users.find(u => u.id === parseInt(req.params.id));
  if (!user) return res.status(404).json({ error: 'User not found' });
  res.json(user);
});

// POST create user
app.post('/api/users', (req, res) => {
  const { name, email } = req.body;
  if (!name || !email) {
    return res.status(400).json({ error: 'Name and email required' });
  }
  const user = { id: users.length + 1, name, email };
  users.push(user);
  res.status(201).json(user);
});

// PUT update user
app.put('/api/users/:id', (req, res) => {
  const user = users.find(u => u.id === parseInt(req.params.id));
  if (!user) return res.status(404).json({ error: 'User not found' });

  const { name, email } = req.body;
  user.name = name || user.name;
  user.email = email || user.email;
  res.json(user);
});

// DELETE user
app.delete('/api/users/:id', (req, res) => {
  const index = users.findIndex(u => u.id === parseInt(req.params.id));
  if (index === -1) return res.status(404).json({ error: 'User not found' });

  users.splice(index, 1);
  res.status(204).send();
});

app.listen(3000, () => console.log('Server running on port 3000'));

Python Flask REST API

from flask import Flask, jsonify, request

app = Flask(__name__)

users = [
    {"id": 1, "name": "Alice", "email": "alice@example.com"},
    {"id": 2, "name": "Bob", "email": "bob@example.com"},
]

@app.route('/api/users', methods=['GET'])
def get_users():
    return jsonify(users)

@app.route('/api/users/<int:user_id>', methods=['GET'])
def get_user(user_id):
    user = next((u for u in users if u['id'] == user_id), None)
    if not user:
        return jsonify({"error": "User not found"}), 404
    return jsonify(user)

@app.route('/api/users', methods=['POST'])
def create_user():
    data = request.get_json()
    user = {
        "id": len(users) + 1,
        "name": data['name'],
        "email": data['email']
    }
    users.append(user)
    return jsonify(user), 201

if __name__ == '__main__':
    app.run(debug=True)

HTTP Status Codes Reference

Code	Meaning	Use Case
200	OK	Successful GET, PUT
201	Created	Successful POST
204	No Content	Successful DELETE
400	Bad Request	Invalid input
401	Unauthorized	Auth required
403	Forbidden	No permission
404	Not Found	Resource missing
500	Server Error	Internal error