What Is Middleware In Django ?

                 What Is Middleware In Django ?

Common Question for Python Django Developer Interviews ? Actually what is Middleware ? What is Role ? How many middleware are there ? can we write own middlewares in a application if yes tell me how ?

Haaahha Now you  also Confused how to answer these questions ?  , when i enter to interview panel i sucked lot of times  , i make it my own ways ..

These are the questions commonly asking for the Interviews , Middleware have main role in our django application so only they asking these questions to everyone. Here I 'm telling you how you can easily tackle with these questions.

What is Middleware ? 

    Middleware is a Middleware is a ................, Dont worry i will help you out , Middleware is a framework of hooks into Django’s request/response processing. It’s a light, low-level “plugin” system for globally altering Django’s input or output. Each middleware component is responsible for doing some specific function.

What are the Common Middleware Classes in Django ? 

MIDDLEWARE_CLASSES = (
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'django.middleware.security.SecurityMiddleware',
)

if you need more details about the each of the middleware classes please follow the link 

middleware classes in django

How to Write Own Middlewares in our project ?

Step 1 :

   if you don't have it you need to create the middleware folder within your app following the Structre.

yourapp/yourapp/middleware

The folder middleware should be placed in the same folder as settings.py , urls , templates

Important : Don't forget to create the __init__.py empty file inside the middleware folder so your app recognize this folder. 

Step 2 :

Create Middleware.

    Now we should create a file for our custon middleware, in this blog let's suppose we want a middleware that filter users based on their IP. we create file called filter_ip_middleware.py the middleware folder with this code

class FilterIPMiddleware(object):
    # Check if client IP is allowed
    def process_request(self, request):
        allowed_ips = ['192.168.1.1', '123.123.123.123', etc...] # Authorized ip's
        ip = request.META.get('REMOTE_ADDR') # Get client IP
        if ip not in allowed_ips:
            raise Http403 # If user is not allowed raise Error

       # If IP is allowed we don't do anything
       return None

Step 3 :

Add the midleware in your 'settings.py' .

   We need to look for the MIDDLEWARE_CLASSES inside the settings.py and there we need to add our middleware( Add it in the last position ) . It should be like.

MIDDLEWARE_CLASSES = (
    'django.middleware.common.CommonMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
     # Above are django standard middlewares

     # Now we add here our custom middleware
     'yourapp.middleware.filter_ip_middleware.FilterIPMiddleware'
)

Step 4 :

DONE ! Now every request from the every client will call your custom middleware and process your

custom code. !

                                                         THANK YOU