Fullstack Flask API: Handling JSON Web Tokens (JWT) and Authorization
In fullstack application development, ensuring secure communication between frontend and backend services is essential. One of the most efficient and modern ways to manage authentication and authorization is by using JSON Web Tokens (JWT). When integrated properly into a Flask API, JWT provides a stateless, scalable, and secure method for verifying users and protecting routes. In this blog, we’ll explore how to handle JWT in Flask APIs and implement robust authorization mechanisms.
🔐 What is JWT?
JWT (JSON Web Token) is an open standard (RFC 7519) used for securely transmitting information between parties as a JSON object. It's digitally signed using a secret (with HMAC) or a public/private key pair (with RSA).
A JWT typically consists of three parts:
Header – specifies the algorithm and token type.
Payload – contains user data (claims).
Signature – verifies that the payload hasn’t been tampered with.
Example:
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eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.
eyJ1c2VyX2lkIjoxMjMsInJvbGUiOiJ1c2VyIn0.
SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c
⚙️ Setting Up JWT in Flask
Step 1: Install Flask-JWT-Extended
bash
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pip install flask-jwt-extended
Step 2: Initialize JWT Manager
python
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from flask import Flask
from flask_jwt_extended import JWTManager
app = Flask(__name__)
app.config['JWT_SECRET_KEY'] = 'your-secret-key'
jwt = JWTManager(app)
🔑 Creating Access Tokens
When a user logs in with valid credentials, generate a JWT token:
python
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from flask_jwt_extended import create_access_token
from flask import request, jsonify
@app.route('/login', methods=['POST'])
def login():
username = request.json.get('username')
password = request.json.get('password')
# Verify user credentials (from database)
if username == 'admin' and password == 'password123':
access_token = create_access_token(identity={'username': username, 'role': 'admin'})
return jsonify(access_token=access_token), 200
return jsonify({"msg": "Invalid credentials"}), 401
🔒 Protecting Routes
You can protect sensitive API routes using the @jwt_required() decorator:
python
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from flask_jwt_extended import jwt_required, get_jwt_identity
@app.route('/dashboard', methods=['GET'])
@jwt_required()
def dashboard():
current_user = get_jwt_identity()
return jsonify(logged_in_as=current_user), 200
🎯 Role-Based Authorization
To restrict access based on user roles:
python
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@app.route('/admin-panel')
@jwt_required()
def admin_panel():
user = get_jwt_identity()
if user['role'] != 'admin':
return jsonify({"msg": "Admins only"}), 403
return jsonify({"msg": "Welcome, admin!"})
🧠 Best Practices
Use HTTPS to protect token transmission.
Set token expiration with JWT_ACCESS_TOKEN_EXPIRES config.
Store tokens securely in HTTP-only cookies or secure storage on the frontend.
Blacklist tokens on logout for enhanced security.
✅ Final Thoughts
JWT simplifies session management in fullstack Flask applications by offering a stateless, scalable approach to authentication and authorization. By integrating Flask-JWT-Extended, developers can easily protect routes, manage user roles, and secure APIs with minimal overhead.
Security is a continuous responsibility—always stay updated with the latest practices and frameworks to keep your APIs safe and efficient.
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