Middleware configuration in Django - Mini Project: Build & Apply

Middleware configuration

📖 Scenario: You are building a Django web application that needs to log every request's path for debugging purposes.

🎯 Goal: Create a custom middleware that logs the request path, then add it to the Django project's middleware settings.

📋 What You'll Learn

Create a custom middleware class named LogRequestMiddleware in a file called middleware.py inside an app named core.

The middleware must have a __call__ method that logs the request path using print().

Add the core.middleware.LogRequestMiddleware to the MIDDLEWARE list in settings.py after django.middleware.common.CommonMiddleware.

💡 Why This Matters

🌍 Real World

Middleware is used in Django projects to add functionality that runs on every request, such as logging, authentication, or security checks.

💼 Career

Understanding middleware configuration is essential for backend developers working with Django to customize request handling and add cross-cutting features.

1

Create the middleware class

In the core/middleware.py file, create a class called LogRequestMiddleware with an __init__ method that accepts get_response and stores it as an instance variable.

Django

# Your code here

Hint

Middleware classes in Django need an __init__ method that takes get_response and saves it.

2

Add the __call__ method to log request path

Add a __call__ method to LogRequestMiddleware that takes request, prints request.path, then returns the response by calling self.get_response(request).

Django

class LogRequestMiddleware:
    def __init__(self, get_response):
        self.get_response = get_response

    # Your code here

Hint

The __call__ method processes each request. Use print(request.path) to log the path.

3

Open settings.py and locate MIDDLEWARE list

Open settings.py and find the MIDDLEWARE list variable. Do not change it yet.

Django

# Open settings.py and find the MIDDLEWARE list
# Your code here

Hint

The MIDDLEWARE list is usually near the top of settings.py.

4

Add custom middleware to MIDDLEWARE list

Add the string 'core.middleware.LogRequestMiddleware' to the MIDDLEWARE list in settings.py immediately after 'django.middleware.common.CommonMiddleware'.

Django

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    # Add your middleware here
]

Hint

Insert your middleware string right after 'django.middleware.common.CommonMiddleware' in the list.

Practice

1. What is the purpose of middleware in a Django project?

easy

A. To create HTML templates

B. To process requests and responses globally before reaching views

C. To define database models

D. To manage user sessions only

Solution

1. Step 1: Understand middleware role

   Middleware runs code on every request and response, acting globally.

2. Step 2: Compare with other options

   Models define data, templates create HTML, sessions are part of middleware but not the only role.

3. Final Answer:

   To process requests and responses globally before reaching views -> Option B

4. Quick Check:

   Middleware = global request/response processing [OK]

Hint: Middleware acts on all requests and responses [OK]

Common Mistakes:

• Confusing middleware with models or templates
• Thinking middleware only manages sessions
• Assuming middleware runs only after views

2. Which of the following is the correct way to add a middleware class in Django's settings.py?

easy

A. 'django.middleware.security.SecurityMiddleware',

B. django.middleware.security.SecurityMiddleware

C. 'SecurityMiddleware',

D. SecurityMiddleware

Solution

1. Step 1: Check syntax for middleware entry

   Middleware classes must be strings with full Python path and comma-separated in list.

2. Step 2: Validate options

   'django.middleware.security.SecurityMiddleware', is a string with full path and comma, correct syntax. Others miss quotes or full path.

3. Final Answer:

   'django.middleware.security.SecurityMiddleware', -> Option A

4. Quick Check:

   Middleware entries are full strings with commas [OK]

Hint: Middleware must be full string path with quotes and comma [OK]

Common Mistakes:

• Omitting quotes around middleware path
• Using only class name without module path
• Missing commas between middleware entries

3. Given this MIDDLEWARE list in settings.py:

[  'django.middleware.security.SecurityMiddleware',  'django.contrib.sessions.middleware.SessionMiddleware',  'django.middleware.common.CommonMiddleware',]

Which middleware runs first on an incoming request?

medium

A. SessionMiddleware

B. CommonMiddleware

C. SecurityMiddleware

D. All run simultaneously

Solution

1. Step 1: Understand middleware order on request

   Middleware runs in the order listed for requests, first listed runs first.

2. Step 2: Identify first middleware in list

   SecurityMiddleware is first, so it runs first on incoming requests.

3. Final Answer:

   SecurityMiddleware -> Option C

4. Quick Check:

   Request middleware order = list order [OK]

Hint: First middleware in list runs first on requests [OK]

Common Mistakes:

• Thinking middleware runs in reverse order on requests
• Assuming all middleware run at the same time
• Confusing request and response middleware order

4. You added a custom middleware class to MIDDLEWARE but Django raises an error on startup. What is a common cause?

medium

A. Middleware class is not a string in MIDDLEWARE list

B. Middleware class missing required methods like __call__ or __init__

C. Middleware class is listed after django.middleware.common.CommonMiddleware

D. Middleware class is defined inside views.py

Solution

1. Step 1: Check middleware list format

   Middleware entries must be strings with full Python path, not class objects.

2. Step 2: Identify common mistake

   Adding the class object instead of string path causes Django startup error.

3. Final Answer:

   Middleware class is not a string in MIDDLEWARE list -> Option A

4. Quick Check:

   MIDDLEWARE entries must be strings [OK]

Hint: Middleware list must contain strings, not class objects [OK]

Common Mistakes:

• Adding middleware as class instead of string path
• Placing middleware in wrong order causing errors
• Defining middleware in wrong file without import

5. You want to add a middleware that modifies the response headers after all other middleware have processed the response. Where should you place it in the MIDDLEWARE list?

hard

A. At the end of the list

B. Right before django.middleware.common.CommonMiddleware

C. Anywhere, order does not matter for response

D. At the beginning of the list

Solution

1. Step 1: Understand middleware response order

   Middleware processes responses in reverse order of the list.

2. Step 2: Place middleware for last response processing

   To modify response after all other middleware (run last on response phase), place at beginning of list since first in list runs last on response.

3. Final Answer:

   At the beginning of the list -> Option D

4. Quick Check:

   Response middleware order = reverse list order [OK]

Hint: First in list runs last on response, put first for final changes [OK]

Common Mistakes:

• Placing middleware at end expecting last response run
• Assuming request and response order are the same
• Ignoring middleware order effects on response