I am trying to use CustomTokenObtainPairView to receive my username in token.

views:

if user.check_password(password):
            # refresh = RefreshToken.for_user(user)
            # refresh.access_token['username'] = user.username
            # token = str(refresh.access_token)
            request.data = {
                'username': username,
                'password': password
            }
            token_response = CustomTokenObtainPairView.post(request=request.data)


            response = Response()
            response.set_cookie(key='jwt', value=token_response.data['access'], httponly=True,     
            secure=True)
            response.data = {
                'access': token_response.data['access']
            }
            return response
        else:
            return Response({'message': 'Wrong password!'}, status=400)

I tried to generate token and adding username in it but it didnot work. If anybody knows how to use TokenObtainPairView in correct way in your function please help.

If you want to change the token claims, you should customize TokenObtainPairSerializer.

my_app/serializers.py

from rest_framework_simplejwt.serializers import TokenObtainPairSerializer
from rest_framework_simplejwt.tokens import Token


class CustomTokenObtainPairSerializer(TokenObtainPairSerializer):
    @classmethod
    def get_token(cls, user) -> Token:
        token = super().get_token(user=user)
        token["username"] = user.username
        return token

settings.py

...
SIMPLE_JWT = {
  "TOKEN_OBTAIN_SERIALIZER": "my_app.serializers.MyTokenObtainPairSerializer",
}
...

If you want to change the way you serve tokens (you may want to use cookies), you should customize the TokenObtainPairView or the TokenRefreshView.

my_app/views.py

from rest_framework import status
from rest_framework.request import Request
from rest_framework.response import Response
from rest_framework_simplejwt.exceptions import TokenError, InvalidToken
from rest_framework_simplejwt.views import TokenObtainPairView


class CustomTokenObtainPairView(TokenObtainPairView):
    def post(self, request: Request, *args, **kwargs) -> Response:
        serializer = self.get_serializer(data=request.data)
        try:
            serializer.is_valid(raise_exception=True)
        except TokenError as e:
            raise InvalidToken(e.args[0])

        response = Response(data=None, status=status.HTTP_200_OK)
        response.set_cookie(key="access", value=serializer.validated_data["access"], httponly=True, secure=True)
        response.set_cookie(key="refresh", value=serializer.validated_data["refresh"], httponly=True, secure=True)
        return response

urls.py

from my_app.views import CustomTokenObtainPairView

urlpatterns = [
    ...
    path('api/token/', CustomTokenObtainPairView.as_view(), name='token_obtain_pair'),
    ...
]

You can do the same for your TokenRefreshView.