Exception middleware in Django - Mini Project: Build & Apply

Create Custom Exception Middleware in Django

📖 Scenario: You are building a Django web application that needs to handle errors gracefully. Instead of showing default error pages, you want to catch exceptions globally and return a simple JSON response with an error message.

🎯 Goal: Build a custom exception middleware in Django that catches all exceptions and returns a JSON response with a message and status code.

📋 What You'll Learn

Create a middleware class named ExceptionMiddleware

Add a __init__ method that accepts get_response

Add a __call__ method that calls get_response and catches exceptions

Return a JSON response with {"error": "An error occurred"} and status code 500 when an exception happens

💡 Why This Matters

🌍 Real World

Web applications often need to handle errors gracefully and provide clear feedback to users or clients, especially APIs that expect JSON responses.

💼 Career

Understanding how to write custom middleware and handle exceptions globally is a valuable skill for backend developers working with Django or similar web frameworks.

1

Create the ExceptionMiddleware class

Create a class called ExceptionMiddleware with an __init__ method that takes get_response as a parameter and stores it in self.get_response.

Django

class ExceptionMiddleware:
    def __init__(self, get_response):
        # Your code here

Need a hint?

The __init__ method is called once when the middleware is created. Store get_response so you can call it later.

2

Add the __call__ method to process requests

Add a __call__ method to ExceptionMiddleware that takes request as a parameter and calls self.get_response(request). Return the response from this call.

Django

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

    def __call__(self, request):
        # Your code here

Need a hint?

The __call__ method handles each request. Call the next middleware or view by calling self.get_response(request).

3

Catch exceptions and return JSON error response

Modify the __call__ method to catch any exception raised by self.get_response(request). If an exception occurs, import JsonResponse from django.http and return JsonResponse({"error": "An error occurred"}, status=500).

Django

from django.http import JsonResponse

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

    def __call__(self, request):
        # Your code here

Need a hint?

Use a try-except block to catch errors. Return a JSON response with status 500 inside the except block.

4

Add middleware to Django settings

Add the string "yourapp.middleware.ExceptionMiddleware" to the MIDDLEWARE list in your Django settings.py file to activate the middleware.

Django

# In settings.py
MIDDLEWARE = [
    # other middleware entries
    # Your code here
]

Need a hint?

Insert the middleware path as a string in the MIDDLEWARE list to enable it.