Why Custom middleware creation in Flask? - Purpose & Use Cases

The Big Idea

What if you could add security checks once and have them work everywhere automatically?

The Scenario

Imagine you want to check every web request to your Flask app for a special token before processing it.

You try adding this check inside every route function manually.

The Problem

Manually adding checks in every route is tiring and easy to forget.

This leads to inconsistent security and duplicated code everywhere.

The Solution

Custom middleware lets you write one piece of code that runs before every request automatically.

This keeps your app clean and secure without repeating yourself.

Before vs After

✗ Before

def route():
    if not check_token():
        return 'Unauthorized'
    # route logic

✓ After

@app.before_request
def check_token_middleware():
    if not check_token():
        return 'Unauthorized'

What It Enables

You can add features like logging, authentication, or error handling globally with one simple middleware.

Real Life Example

A website that blocks users without a valid login token from accessing any page by checking the token once in middleware.

Key Takeaways

Manual checks in every route cause repeated code and mistakes.

Middleware runs code automatically before requests.

Custom middleware keeps your app organized and secure.