Getting Started with Django Handlers

Introduction

Let’s imagine that we have a django application and we want to create REST API for it.

Our API should have two urls:

• /records/ for GET and POST requests
• /records/{record_id}/ for GET, PUT, and DELETE requests

Installation

Firstly, we need to install django-handlers:

$ pip install django-handlers

Creating Handler

It is very simple to create a handler. The best place for it is our views file:

from django_handlers import Handler

handler = Handler()

Adding Endpoints

Let’s add a view for handling of GET requests:

@handler.get('records')
def view_records(request):
    records = Record.objects.all()
    return JsonResponse({
        'records': [record.data for record in records]
    })

‘records’ is an endpoint name. Endpoint is a simple callable that delegates request handling to a view associated with an HTTP method.

Let’s add to the same endpoint a view for handling of POST requests:

@handler.post('records')
def add_record(request):
    form = RecordForm(json.loads(request.body))

    if form.is_valid():
        record = form.save()
        return JsonResponse(record.data)

    return JsonResponse(form.errors, status=422)

Now we have endpoint ‘records’ with two views. We can associate the endpoint with an url:

from .views import handler

urlpatterns = [
    url(r'^records/$', handler.records),
]

Now view_records handles GET requests and add_record handles POST requests to url ‘/records/’. Let’s add views to another endpoint:

@handler.get('record')
def view_record(request, record_id):
    record = get_object_or_404(Record, id=record_id)
    return JsonResponse(record.data)


@handler.put('record')
def change_record(request, record_id):
    record = get_object_or_404(Record, id=record_id)
    form = RecordForm(json.loads(request.body), instance=record)

    if not form.is_valid():
        return JsonResponse(form.errors, status=422)

    form.save()
    return JsonResponse({})


@handler.delete('record')
def delete_record(request, record_id):
    record = get_object_or_404(Record, id=record_id)
    record.delete()
    return JsonResponse({})


# Note that also views can be added via add_view method:

# handler.add_view('get', 'record', view_record)
# handler.add_view('put', 'record', change_record)
# handler.add_view('delete', 'record', delete_record)

We should add new url and associate endpoint ‘record’ with it:

urlapatterns = [
    url(r'^records/$', handler.records),
    url(r'^records/(\d+)/$', handler.record),
]

Adding Hooks

You might notice that our views have some code duplication. We can decrease it by using hooks:

@handler.before('record')
def before_record(request, record_id):
    request.record = get_object_or_404(Record, id=record_id)


@handler.get('record')
def view_record(request, record_id):
    return JsonResponse(request.record.data)


@handler.put('record')
def change_record(request, record_id):
    form = RecordForm(json.loads(request.body), instance=request.record)

    if not form.is_valid():
        return JsonResponse(form.errors, status=422)

    form.save()
    return JsonResponse({})


@handler.delete('record')
def delete_record(request, record_id):
    request.record.delete()
    return JsonResponse({})

Now before_record will be called before each view of endpoint ‘record’. Also you can add hook to be called after each view of specified endpoint:

@handler.after('record')
def after_record(request, record_id):
    do_something()

Using Decorators

Of course, you can decorate you views but sometimes it is not enough (for example, in case of csrf_exempt) and you want to decorate your endpoints.

To decorate all handler endpoints you can pass decorators via argument for __init__ method:

handler = Handler(decorators=[csrf_exempt, my_decorator])

To decorate specific endpoint you can use decorate method:

handler.decorate('something', my_decorator)
handler.decorate('something', [csrf_exempt, my_decorator])