Jaewoong Lee

I'm Programmer for KAIST.

Django Standard API Response Middleware for DRF

07 Jan 2020 » python, django

As you can see, if you using django-rest-framework, you will found many different response format. This middleware to solve all of these problems with Standard API Response.

All HTTP Response status stored into json response, not in HTTP Status (because mobile application, like android can’t fetch the response body when HTTP Status >= 400).

middleware.py

import json
import copy

from django.utils.deprecation import MiddlewareMixin
from django.utils.translation import ugettext_lazy as _
from django.core.serializers.json import DjangoJSONEncoder

from rest_framework import status


class BaseAPIResponseMiddleware(MiddlewareMixin):

    def render_response(self, response):
        """
        function to fixed the response API following with this format:

        [1] success single
            {
             "status": 200,
             "success": true,
             "message": "The success message",
             "result": {}
            }

        [2] success list
            {
               "status": 200,
               "success": true,
               "message": null,
               "results": [],

               "count": 2,
               "page_size": 5,
               "current_page": 1,
               "next": "/api/post/?page=2&search=a",
               "previous": null
            }

        [3] failed
            {
               "status": 400,
               "success": false,
               "message": "The failed message",
               "result": {}
            }
        """
        default_response_keys = ('status', 'status_http', 'detail', 'message',
                                 'success', 'non_field_errors', 'count',
                                 'page_size', 'current_page', 'next',
                                 'previous', 'result', 'results')
        response_data = copy.deepcopy(response.data)

        # setup default result if doesn't exist
        if not any(['result' in response_data, 'results' in response_data]):
            response_data.update({'result': {}})

        # setup default message into response data
        if 'message' not in response_data:
            response_data.update({'message': None})

        # store the status_code into response data
        if 'status' not in response_data:
            response_data.update({'status': response.status_code})

        # store the status_http into response data
        if 'status_http' not in response_data:
            response_data.update({'status_http': response.status_code})

        # updating the response message
        if 'detail' in response_data:
            response_data.update({'message': response_data.get('detail')})
            del response_data['detail']

        elif 'non_field_errors' in response_data:
            response_errors = '<br />'.join(response_data.get('non_field_errors'))
            response_data.update({'message': response_errors})
            del response_data['non_field_errors']

        # store the success boolean into response data
        if response.status_code >= 400:
            response_errors = []
            response_errors_keys = []

            for (key, value) in response_data.items():
                if key not in default_response_keys:
                    errors = ' '.join([str(v) for v in value])
                    errors = '%s: %s' % (key, errors)
                    response_errors.append(errors)
                    response_errors_keys.append(key)

            if len(response_errors) > 0:
                response_errors = '<br />'.join(response_errors)
                response_data.update({'message': response_errors})

            # deleting the errors in the field keys.
            if len(response_errors_keys) > 0:
                list(map(response_data.pop, response_errors_keys))

            if not response_data.get('message'):
                response_data.update({'message': _('Failed')})

            response_data.update({'success': False,
                                  'status_http': status.HTTP_200_OK})

        elif response.status_code >= 100:
            if not response_data.get('message'):
                response_data.update({'message': _('Success')})

            if 'success' not in response_data:
                response_data.update({'success': True})

        return response_data

    def process_response(self, request, response):
        # use default response if it setup.
        if request.headers.get('Use-Default-Response'):
            return response

        if hasattr(response, 'data') and isinstance(response.data, dict):
            try:
                response_data = self.render_response(response)
                response.status_code = response_data.get('status_http')

                if 'status_http' in response_data:
                    del response_data['status_http']

                response.data = response_data
                response.content = json.dumps(response_data, cls=DjangoJSONEncoder)
            except Exception:
                pass

        # handle error response but without `response.data`
        # this error response specific for "Server Error" mode.
        response_format = request.headers.get('Response-Format')
        if (response.status_code >= 500) and (response_format == 'application/json'):
            response_data = {'success': False, 'result': {},
                             'status': response.status_code,
                             'message': response.reason_phrase}
            response.status_code = 200
            response.data = response_data
            response.content = json.dumps(response_data, cls=DjangoJSONEncoder)
            response['Content-Type'] = 'application/json'

        return response

paginator.py

from __future__ import unicode_literals

from collections import OrderedDict

from django.conf import settings
from django.utils.translation import ugettext_lazy as _

from rest_framework import status
from rest_framework.response import Response
from rest_framework.pagination import (PageNumberPagination, LimitOffsetPagination)


class RestPagination(PageNumberPagination, LimitOffsetPagination):
    """
    class FoobarPagiantion(RestPagination):
        page_size = 10

    class FoobarView(ListAPIView):
        pagination_class = FoobarPagiantion
    """

    def paginate_queryset(self, queryset, request, view=None):
        limit = request.query_params.get('limit')
        if str(limit).isdigit():
            self.page_size = int(limit)
        return super().paginate_queryset(queryset, request, view=view)

    def get_paginated_response(self, results):
        next_link = self.get_next_link() or ''
        prev_link = self.get_previous_link() or ''

        if getattr(settings, 'USE_SSL', False):
            next_link = next_link.replace('http:', 'https:')
            prev_link = prev_link.replace('http:', 'https:')

        return Response(OrderedDict([
            ('count', self.page.paginator.count),
            ('page_size', self.page_size),
            ('current_page', self.page.number),
            ('next', next_link or None),
            ('previous', prev_link or None),
            ('status', status.HTTP_200_OK),
            ('message', _('Success')),
            ('success', True),
            ('results', results)
        ]))

When you want to implement for specific feature by using default response, e.g: I want to use it in my webhook, then you can also use the wrapper to do it. For example in your wrappers.py

def use_default_response(view_func):
    """
    function wrapper to rollback `BaseAPIResponseMiddleware`
    into default response middleware.
    """
    def wrapper_function(request, *args, **kwargs):
        request.META['HTTP_USE_DEFAULT_RESPONSE'] = True
        return view_func(request, *args, **kwargs)
    return wrapper_function

then, in your specific view;

from path.to.wrappers import use_default_response
from django.utils.decorators import method_decorator


class WebhookView(APIView):

    @method_decorator(use_default_response)
    def post(self, request, *args, **kwargs):
        pass