This tutorial will guide you on how to effectively manage middleware execution order in Django. Middleware is a critical component in Django as it allows the developer to process request and response globally before reaching the view and after leaving the view respectively.
By the end of this tutorial, you will be able to:
- Understand what middleware is and why the order of execution is important
- Know how to manage the order of middleware in Django
- Write middleware and add it to your Django project
Before starting this tutorial, you should have a basic understanding of Python and Django. Familiarity with Django's request/response process will be beneficial.
In Django, middleware is a series of hooks into Django’s request/response processing. It's a way to pre-process requests and post-process responses. Middleware classes are executed in a specific order defined in the MIDDLEWARE setting in your Django project's settings module.
The order in which middleware are processed is significant. Middleware classes specified first are run last when the response returns from the view. However, they're run first upon request before the view. In other words, the order is top-down for requests and bottom-up for responses.
class SimpleMiddleware:
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
# Code to be executed for each request before
# the view (and later middleware) are called.
response = self.get_response(request)
# Code to be executed for each request/response after
# the view has been called.
return response
This code defines a basic middleware. Before the view is called, code above self.get_response(request) is executed. After the view is called, code below is executed.
In your settings file, you might have:
MIDDLEWARE = [
'django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
]
The CommonMiddleware will be processed before the AuthenticationMiddleware on a request, but after on a response.
MIDDLEWARE setting determines the order of execution.MIDDLEWARE setting. Observe any changes in the execution order.Solution and explanation for Exercise 1
class PrintMiddleware:
def __init__(self, get_response):
self.get_response = get_response
def __call__(self, request):
print("Before view")
response = self.get_response(request)
print("After view")
return response
This middleware prints "Before view" before the view is called and "After view" after the view is called.
The solution and explanation for the other exercises are left as an exercise for the reader. You can try them out and check your understanding of the concept.