Custom middleware creation in Flask - Mini Project: Build & Apply

Custom middleware creation

📖 Scenario: You are building a simple Flask web app that needs to log every request's path before processing it.This helps you understand how middleware can intercept requests to add extra behavior.

🎯 Goal: Create a custom middleware in Flask that logs the request path for every incoming request.

📋 What You'll Learn

Create a Flask app instance named app

Define a middleware function named log_request_path

Use the middleware to log the request path before each request

Add a simple route /hello that returns 'Hello, World!'

💡 Why This Matters

🌍 Real World

Middleware is used in web apps to add features like logging, authentication, or request modification without changing route code.

💼 Career

Understanding middleware is important for backend developers working with Flask or similar web frameworks to build scalable and maintainable web services.

1

Create the Flask app instance

Create a Flask app instance called app using Flask(__name__).

Flask

# Create the Flask app instance
# Your code here

Need a hint?

Use Flask(__name__) to create the app instance.

2

Define the middleware function

Define a function called log_request_path that takes no arguments and logs the current request path using print(request.path). Import request from flask.

Flask

from flask import Flask
from flask import request

app = Flask(__name__)

# Define the middleware function
# Your code here

Need a hint?

Import request and define a function that prints request.path.

3

Register the middleware with before_request

Use @app.before_request decorator to register the log_request_path function as middleware that runs before each request.

Flask

from flask import Flask
from flask import request

app = Flask(__name__)

def log_request_path():
    print(request.path)

# Register the middleware
# Your code here

Need a hint?

Use @app.before_request decorator to add the middleware function.

4

Add a simple route to test

Add a route /hello using @app.route('/hello') that returns the string 'Hello, World!'.

Flask

from flask import Flask
from flask import request

app = Flask(__name__)

@app.before_request
def log_request_path():
    print(request.path)

# Add the /hello route
# Your code here

Need a hint?

Use @app.route('/hello') decorator and define a function that returns the greeting.