Django Rest Framework – invalid credentials – can not Login via Postman

Question

I’m working on web app where you can register and login via Postman. Register is working fine. Here is serializer.py

from rest_framework import serializers
from django.contrib.auth.models import User
from rest_framework_simplejwt.tokens import RefreshToken
from django.contrib.auth import authenticate


class RegisterSerializer(serializers.Serializer):
    first_name = serializers.CharField()
    last_name = serializers.CharField()
    username = serializers.CharField()
    password = serializers.CharField()

    def validate(self, data):
        if User.objects.filter(username=data["username"]).exists():
            raise serializers.ValidationError("username is already taken")

        return data

    def create(self, validated_data):
        user = User.objects.create(first_name=validated_data["first_name"],
                                   last_name=validated_data["last_name"],
                                   username=validated_data["username"].lower()
                                   )
        user.set_password(validated_data["password"])

        return validated_data




class LoginSerializer(serializers.Serializer):
    username = serializers.CharField()
    password = serializers.CharField()

    def validate(self, data):

        if not User.objects.filter(username=data["username"]).exists():
            raise serializers.ValidationError("account not found")

        return data

    def get_jwt_token(self, data):

        user = authenticate(username=data["username"], password=data["password"])

        if not user:
            return {"message": "invalid credentials", "data": {}}

        refresh = RefreshToken.for_user(user)

        return {
            "message": "login success",
            "data": {"token": {"refresh": str(refresh),
            "access": str(refresh.access_token)}}}

Here is views.py

from rest_framework.views import APIView
from rest_framework.response import Response
from .serializer import RegisterSerializer, LoginSerializer
from rest_framework import status


class RegisterView(APIView):
    def post(self, request):
        try:
            data = request.data

            serializer = RegisterSerializer(data=data)

            if not serializer.is_valid():
                return Response ({
                    "data" : serializer.errors,
                    "message" : "something went wrong",
                }, status=status.HTTP_400_BAD_REQUEST)

            serializer.save()

            return Response({
                "data" : {},
                "message" : "user created successfully",
                }, status=status.HTTP_201_CREATED)



        except Exception as e:
            print(e)
            return Response({
                "data" : {},
                "message" : "something went wrong",
            }, status=status.HTTP_400_BAD_REQUEST)


class LoginView(APIView):

    def post(self,request):
        try:
            data = request.data
            serializer = LoginSerializer(data=data)

            if not serializer.is_valid():
                return Response({
                "data": serializer.errors,
                "message": "something went wrong",
            }, status=status.HTTP_400_BAD_REQUEST)

            response = serializer.get_jwt_token(serializer.data)

            return Response(response, status=status.HTTP_200_OK)

        except Exception as e:
            print(e)
            return Response({
                "data" : {},
                "message" : "something went wrong",
            }, status=status.HTTP_400_BAD_REQUEST)

In Postman Register works fine

But if I want to login:

I don’t know why it is not working. I read jwt documentation and I think that I have it right.

I don’t have any more screenshot. If you want see rest of the code I can post it.

Asked By: Balage

||

Source

Answer 1

The problem seems to be with this line of code

user = authenticate(username=data["username"], password=data["password"])

put a breakpoint and look if the values being passed match the values in your database.
Make sure that the AUTHENTICATION_BACKENDS setting in your Django settings includes the django.contrib.auth.backends.ModelBackend backend. If this setting is missing or incorrect, the authenticate function may not work properly.

You should also check the value of the data dictionary to make sure that the username and password fields are being passed correctly from the request. You can print out the data dictionary or use a debugger to inspect its contents.

In addition to using a breakpoint, you could also try logging the return value of the authenticate function to see if it is returning a valid user object. If the authenticate function is not able to authenticate the user, it will return None.

If the authenticate function is returning None, you should check that the password for the user is correctly hashed and stored in the database. If the password is not hashed correctly, the authenticate function will not be able to match it against the stored password hash.

Answered By: Seppe Willems

Django Rest Framework – invalid credentials – can not Login via Postman

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