无法获取REQUEST中REDIRECT_FIELD_NAME对应的值。

loginview.py

from django.conf import settings
from django.contrib.auth import login, REDIRECT_FIELD_NAME
from .forms import LoginForm, ResetPasswordForm
from django.utils.decorators import method_decorator
from django.views.generic import FormView
from django.views.decorators.cache import never_cache
from django.views.decorators.csrf import csrf_protect


class LoginView(FormView):

    template_name = 'login.html'
    form_class = LoginForm

    @method_decorator(csrf_protect)
    @method_decorator(never_cache)
    def dispatch(self, *args, **kwargs):
        return super(LoginView, self).dispatch(*args, **kwargs)

    def set_test_cookie(self):
        self.request.session.set_test_cookie()

    def check_and_delete_test_cookie(self):
        if self.request.session.test_cookie_worked():
            self.request.session.delete_test_cookie()
            return True
        return False

    def get(self, request, *args, **kwargs):
        self.set_test_cookie()
        return super(LoginView, self).get(self, request, *args, **kwargs)

    def form_valid(self, form):
        self.check_and_delete_test_cookie()
        login(self.request, form.get_user())
        return super(LoginView, self).form_valid(form)

    def form_invalid(self, form):
        self.set_test_cookie()
        return super(LoginView, self).form_invalid(form)

    def get_context_data(self, **kwargs):
        context = super(LoginView, self).get_context_data(**kwargs)
        context['second_form'] = ResetPasswordForm
        return context

    def get_success_url(self):
        if self.success_url:
            redirect_to = self.success_url
        else:
            # 问题已定位，这里无法获取next的值，求解
            redirect_to = self.request.REQUEST.get(REDIRECT_FIELD_NAME, '')
        host_name = urlparse(redirect_to)[1]
        dir_name = urlparse(redirect_to)[2]
        if not redirect_to:
            redirect_to = settings.LOGIN_REDIRECT_URL
        elif dir_name.lower() == '/logout':
            redirect_to = settings.LOGIN_REDIRECT_URL
        elif host_name and host_name != self.request.get_host():
            redirect_to = settings.LOGIN_REDIRECT_URL
        return redirect_to