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Django API Server

Open-source Django API server that explains how to extend an existing codebase

This sample explains how to extend an existing Django API Starter and add another model managed via a new API node.

✅ Codebase structure​

PROJECT ROOT
├── api                           # App containing all project-specific apps
│   ├── apps.py
│   ├── authentication            # Implements authentication app logic (register, login, session) logic
│   │   ├── apps.py
│   │   ├── backends.py           # Handles the active session authentication
│   │   ├── migrations
│   │   ├── serializers
│   │   ├── tests.py              # Test for login, registration and session
│   │   └── viewsets
|   |
│   ├── fixtures                  # Package containg the project fixtures
│   ├── __init__.py
│   ├── routers.py                # Define api routes
│   └── user                      # Implements user app logic
|
├── core                         # Implements app logic
│   ├── asgi.py
│   ├── __init__.py
│   ├── settings.py              # Django app bootstrapper
│   ├── test_runner.py           # Custom  test runner
│   ├── urls.py
│   └── wsgi.py
|
├── docker-compose.yml
├── Dockerfile
├── .env                         # Inject Configuration via Environment
├── manage.py                    # Starts the app
└── requirements.txt             # Contains development packages

✅ Used Patterns​

Working with Django Rest Framework, the most common design pattern is the Template Method Pattern.

It mostly consists of providing base/skeleton for some features with the possibility to override/extends these skeletons.

For example, you can check the code in api/user/viewsets.py. The UserViewSet inherits of viewsets.GenericsViewSet and CreateModelMixin and UpdateModelMixin.

The UpdateModelMixin provides the logic to update an object using PUT.

We only need to rewrite the method which handles the updating and provides the serializer_class and the permission_classes.

✅ How to use the API​

POSTMAN usage

The API is actually built around these endpoints :

  • api/users/signup
  • api/users/login
  • api/users/edit
  • api/users/checkSession
  • api/users/logout

Register - api/users/register

POST api/users/register
Content-Type: application/json

{
    "username":"test",
    "password":"pass",
    "email":"test@appseed.us"
}

Response :

{
    "success": true,
    "userID": 1,
    "msg": "The user was successfully registered"
}

Login - api/users/login

cd api && django-admin startapp transactions

Once it's done, rewrite the apps.py file with the following content.


POST /api/users/login
Content-Type: application/json

{
    "password":"pass",
    "email":"test@appseed.us"
}

Response :

{
    "success": true,
    "token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpZCI6MSwiZXhwIjoxNjI4NzgxNTY4fQ.mB_YcZxZJd37r_4NYnLYeCByEHKGBC2ob0xe9KgcOII",
    "user": {
        "_id": 1,
        "username": "test",
        "email": "test@appseed.us"
    }
}

Logout - api/users/logout

POST api/users/logout
Content-Type: application/json
authorization: JWT_TOKEN (returned by Login request)

{
    "token":"JWT_TOKEN"
}

Response :

{
    "success": true,
    "msg": "Token revoked"
}

cURL usage

Let's edit information about the user and check a session using cURL.

Check Session- api/users/checkSession

curl --request POST \
  --url http://127.0.0.1:8000/api/users/checkSession \
  --header 'Authorization: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpZCI6MSwiZXhwIjoxNjI4NzgxNTY4fQ.mB_YcZxZJd37r_4NYnLYeCByEHKGBC2ob0xe9KgcOII' \
  --header 'Content-Type: application/json'

Response :

{
  "success": true
}

Edit User - api/users/edit

curl --request POST \
  --url http://127.0.0.1:8000/api/users/edit \
  --header 'Authorization: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpZCI6MSwiZXhwIjoxNjI4NzgxNTY4fQ.mB_YcZxZJd37r_4NYnLYeCByEHKGBC2ob0xe9KgcOII' \
  --header 'Content-Type: application/json' \
  --data '{
    "username": "tester",
    "email": "test@admin.us",
    "userID": 1
}'

Response :

{
  "success": true
}

✅ How to extend API​

Add a new model - transactions

To add a model for transaction in the project, let's create a new application in the api directory.

  • Creating the app using django-admin command in the api directory.
  • Then modify the name and the label of the app in apps.py
  • And add the app in the INSTALLED_APPS in the settings.py of the project.
cd api && django-admin startapp transaction

Then modify the apps.py file.

# api/transaction/apps.py

from django.apps import AppConfig 

class TransactionConfig(AppConfig):
    default_auto_field = 'django.db.models.BigAutoField'
    name = 'api.transaction'
    label = 'api_transaction'

And don't forget to add the default_app_config in the __init__.py file the transaction directory.

# api/transaction/__init__.py

default_app_config = "api.transaction.apps.TransactionConfig"

We can now register the application in settings.py file.

# core/settings.py

INSTALLED_APPS = [
    ...
    "api.authentication",
    "api.transaction"
]

Add API interface to manage transactions

Creating an API interface to manage transactions usually go this way :

  • Creating the model
  • Creating the serializer
  • Write the views or the viewsets
  • Register the viewsets by creating routes

We've already created the model for transaction.

Let's create the serializer.

A serializer allows us to convert complex Django complex data structures such as querysets or model instances in Python native objects that can be easily converted JSON/XML format, but a serializer also serializes JSON/XML to naive Python.

# api/transaction/serializers.py

from api.transaction.models import Transaction
from rest_framework import serializers

class TransactionSerializer(serializers.ModelSerializer):
    info = serializers.CharField(allow_null=True, allow_blank=True)
    price = serializers.IntegerField(required=True)

    class Meta:
        model = Transaction
        fields = ["id", "product", "price", "qty", "discount", "info"]
        read_only_field = ["id", "created"]

And now the viewsets.

The routes for the transaction interface API should look like this :

  • api/transactions/create -> create transaction
  • api/transactions/edit/id-> edit transaction
  • api/transactions/delete/id -> delete transaction
  • api/transactions/get/id -> get specific transaction
  • api/transactions/get -> get all transactions

The ViewSet class comes with built-in actions :

  • list
  • retrieve
  • create
  • update
  • partial_update
  • destroy

And to make sure the names of the URLs match what we need, we'll be using actions.

First of all, create a file name viewsets in the transactions directory.

And add the following code.

# api/transactions/viewsets.py

from rest_framework import viewsets, status
from rest_framework.response import Response
from rest_framework.exceptions import ValidationError, NotFound, MethodNotAllowed
from rest_framework.decorators import action
from rest_framework.permissions import IsAuthenticated

from django.core.exceptions import ObjectDoesNotExist

from api.transaction.models import Transaction
from api.transaction.serializers import TransactionSerializer


class TransactionViewSet(viewsets.ModelViewSet):
    serializer_class = TransactionSerializer
    permission_classes = (IsAuthenticated,)
    http_method_names = ['get', 'post']

    not_found_message = {"success": False, "msg": "This object doesn't exist."}
    missing_id_message = {"success": False, "msg": "Provide a transaction id."}

Then let's rewrite the get_queryset method. This method is used by the viewset to return a list of objects, here a list of transactions.

class TransactionViewSet(viewsets.ModelViewSet):
    ...

    def get_queryset(self):
        return Transaction.objects.all()

Great. Now, let's make sure DRF will exactly match the URLs we want. First of all, we have to block the default routes.

class TransactionViewSet(viewsets.ModelViewSet):
    ...

    def list(self, request, *args, **kwargs):
        raise MethodNotAllowed('GET')

    def create(self, request, *args, **kwargs):
        raise MethodNotAllowed('POST')

    def destroy(self, request, *args, **kwargs):
        raise MethodNotAllowed('DELETE')

    def update(self, request, *args, **kwargs):
        raise MethodNotAllowed('PUT')

    def retrieve(self, request, *args, **kwargs):
        raise MethodNotAllowed('GET')

And we can write our own actions now.

Let's start with api/transactions/create.

class TransactionViewSet(viewsets.ModelViewSet):
    ...

    @action(methods=['post'], detail=False, url_path='create')
    def create_transaction(self, request, *args, **kwargs):
        data = request.data

        serializer = self.serializer_class(data=data)
        serializer.is_valid(raise_exception=True)
        serializer.save()

        return Response({
            "success": True
        }, status.HTTP_201_CREATED)

To avoid name collision with the default built-in method create , we are naming the method create_transaction. Hopefully, DRF provides the option to specify the url_path of the method.

Let's write the actions for api/transactions/get and api/transactions/get/id

class TransactionViewSet(viewsets.ModelViewSet):
    ...

    @action(methods=['get'], detail=False, url_path='get')
    def get_transactions(self, request, *args, **kwargs):

        transactions = self.get_queryset()

        page = self.paginate_queryset(transactions)

        if page is not None:
            serializer = self.get_serializer(page, many=True, context=self.get_serializer_context())
            return self.get_paginated_response(serializer.data)

        serializer = self.get_serializer(transactions, many=True, context=self.get_serializer_context())
        return Response({
            "success": True,
            "transactions": serializer.data
        }, status=status.HTTP_200_OK)

    @action(methods=['get'], detail=False, url_path=r'get/(?P<transaction_id>\w+)')

    def get_transaction(self, request, transaction_id=None, *args, **kwargs):

        if transaction_id is None:
            raise ValidationError(self.missing_id_message)

        try:
            obj = Transaction.objects.get(pk=transaction_id)
        except ObjectDoesNotExist:
            raise NotFound(self.not_found_message)

        serializer = self.get_serializer(obj)

        return Response({
            "success": True,
            "transaction": serializer.data
        }, status=status.HTTP_200_OK)

Notice that for the get/id (get_transaction), we are writing the url_path using regex expression.

And finally, the actions for api/transactions/delete/id and api/transactions/edit.

class TransactionViewSet(viewsets.ModelViewSet):
    ...
    @action(methods=['post'], detail=False, url_path=r'edit/(?P<transaction_id>\w+)')
    def edit_transaction(self, request, transaction_id=None, *args, **kwargs):

        if transaction_id is None:
            raise ValidationError(self.missing_id_message)

        try:
            obj = Transaction.objects.get(pk=transaction_id)
        except ObjectDoesNotExist:
            raise NotFound(self.not_found_message)

        serializer = self.get_serializer(obj, data=request.data, partial=True)
        serializer.is_valid(raise_exception=True)
        self.perform_update(serializer)

        if getattr(obj, "_prefetched_objects_cache", None):
            obj._prefetched_objects_cache = {}

        return Response({
            "success": True
        }, status.HTTP_200_OK)

    @action(methods=['post'], detail=False, url_path=r'delete/(?P<transaction_id>\w+)')
    def delete_transaction(self, request, transaction_id=None, *args, **kwargs):

        if transaction_id is None:
            raise ValidationError(self.missing_id_message)

        try:
            obj = Transaction.objects.get(pk=transaction_id)
        except ObjectDoesNotExist:
            raise NotFound(self.not_found_message)

        obj.delete()

        return Response({
            "success": True
        }, status.HTTP_200_OK)

Now, we can register the viewset.

There is already a routers.py file which contains the routes for api/users.

Let's create a different router for transactions.

In the api directory, create a new package called routers. Move the file routers.py in it and rename it to users.py.

Then create a new file named transactions.py and add the following code to register TransactionViewSet actions.

# api/routers/transactions.py

from rest_framework import routers

from api.transaction.viewsets import TransactionViewSet

router = routers.SimpleRouter(trailing_slash=False)

router.register('', TransactionViewSet, basename='transactions')

urlpatterns = [
    *router.urls,
]

And the last step, open the urls.py file in the core directory and add the transaction router.

# core/urls.py

from django.urls import path, include

urlpatterns = [
    path("api/users/", include(("api.routers.users", "api-users"), namespace="api-users")),
    path("api/transactions/", include(("api.routers.transactions", "api-transactions"), namespace="api-transactions"))
]

At this point, you can start testing the API with Postman.

In summary, You just learned :

  • How to add a new model;
  • How to add a serializer for this model;
  • How to rewrite viewset behavior and actions to match your needs.

✅ Resources​