What is Django middleware and how does it work?

Question

Accepted Answer

**Django middleware** is a framework of **hooks into request/response processing**.

```python
# settings.py
MIDDLEWARE = [
    "django.middleware.security.SecurityMiddleware",
    "django.contrib.sessions.middleware.SessionMiddleware",
    "django.middleware.common.CommonMiddleware",
    "django.middleware.csrf.CsrfViewMiddleware",
    "myapp.middleware.TimingMiddleware",
]

# myapp/middleware.py
import time

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

def __call__(self, request):
        # Before view
        start_time = time.time()

response = self.get_response(request)

# After view
        duration = time.time() - start_time
        response["X-Process-Time"] = str(duration)
        return response

def process_exception(self, request, exception):
        # Handle exceptions
        pass

def process_template_response(self, request, response):
        # Modify template responses
        return response
```

**Execution order:**
- Request: top to bottom.
- Response: bottom to top.

**Built-in middleware:**
- `SecurityMiddleware` — HTTPS, HSTS.
- `SessionMiddleware` — session handling.
- `CsrfViewMiddleware` — CSRF protection.
- `AuthenticationMiddleware` — user sessions.

Python: What is Django middleware and how does it work?