Django rest_framework custom error message

Question

I have a API endpoint where it will do input validation using rest_framework's serializer.is_valid() where it will return custom error message and response.

serializer = FormSerializer(data=data)
if not serializer.is_valid(raise_exception=False):
    return Response({"Failure": "Error"}, status=status.HTTP_400_BAD_REQUEST)

Is it possible to populate validation errors without using the generic response provided by raise_exception=True? I am trying to avoid using the generic response as it will display all the validation errors if there are more than one error.

The response will be something like

return Response(
     {
          "Failure": "Error", 
          "Error_list": {"field1": "This field is required"}
     },
     status=status.HTTP_400_BAD_REQUEST
)

JPG · Accepted Answer · 2018-08-03 05:04:05Z

13

Create a Custom Exception class as,

from rest_framework.exceptions import PermissionDenied
from rest_framework import status


class MyCustomExcpetion(PermissionDenied):
    status_code = status.HTTP_400_BAD_REQUEST
    default_detail = "Custom Exception Message"
    default_code = 'invalid'

    def __init__(self, detail, status_code=None):
        self.detail = detail
        if status_code is not None:
            self.status_code = status_code

Why I'm inherrited from PermissionDenied exception class ??
see this SO post -- Why DRF ValidationError always returns 400

Then in your serializer, raise exceptions as,

class SampleSerializer(serializers.ModelSerializer):
    class Meta:
        fields = '__all__'
        model = SampleModel

    def validate_age(self, age):  # field level validation
        if age > 10:
            raise MyCustomExcpetion(detail={"Failure": "error"}, status_code=status.HTTP_400_BAD_REQUEST)
        return age

    def validate(self, attrs): # object level validation
        if some_condition:
            raise MyCustomExcpetion(detail={"your": "exception", "some_other": "key"}, status_code=status.HTTP_410_GONE)
        return attrs

age and name are two fields of SampleModel class

Response will be like this

By using this method,
1. You can customize the JSON Response
2. You can return any status codes
3. You don't need to pass True in serializer.is_valid() method (This is not reccomended)

edited Aug 3, 2018 at 5:04

answered Aug 3, 2018 at 4:45

JPG

89.4k24 gold badges164 silver badges235 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Clueless_Coder Over a year ago

Is it possible to catch field validation error in the object level validation? I have more than 20 fields and wish to just capture the first field validation error in the object level validation.

JPG Over a year ago

According to my example, you will get the value of your field by attrs['your_field']. Then check specific validation by yourself. If validation fails, raise the CustomException

Clueless_Coder Over a year ago

So it is not possible if I were using name = serializers.CharField(max_length=10) as my field validation and catch it in the object level validation?

JPG Over a year ago

In that case, it will raise an HTTP 400 Bad Request only if you are set raise_exception=True in is_valid() ->> (is_valid(True))

JPG Over a year ago

@Clueless_Coder Is there any problem?

neverwalkaloner · Accepted Answer · 2018-08-03 04:25:19Z

2

You can write custom error handler:

from rest_framework.views import exception_handler

def custom_exception_handler(exc, context):
    response = exception_handler(exc, context)
    if response is not None:
        response.data['Failure'] = 'Error'

    return response

answered Aug 3, 2018 at 4:25

neverwalkaloner

47.6k7 gold badges101 silver badges103 bronze badges

1 Comment

neverwalkaloner Over a year ago

@JerinPeterGeorge yes. It only add "Failure": "Error", to response.

Unicorn Tears · Accepted Answer · 2019-08-15 13:07:07Z

2

A simple way is to use one of the exception messages, eg NotFound. See docs

# views.py
from rest_framework.exceptions import NotFound

class myview(viewsets.ModelViewSet):
    def perform_create(self, serializer):
        raise NotFound("My text here")

That will return a 404 and change the response to your text

HTTP 404 Not Found
Allow: GET, POST, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept
{
    "detail": "my text here"
}

answered Aug 15, 2019 at 13:07

Unicorn Tears

3762 silver badges6 bronze badges

Collectives™ on Stack Overflow

Django rest_framework custom error message

3 Answers 3

5 Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

5 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related