Django ClassBasedView中未显示成功消息

我想保存表单后显示成功消息 . 我正在使用message framework

settings.py

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
]

MIDDLEWARE_CLASSES = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [TEMPLATE_PATH],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

views.py

class VolunteerCreateView(SuccessMessageMixin, CreateView):
    model = Volunteer
    form_class = VolunteerForm
    template_name = 'volunteer.html'
    success_message = 'Thank you!'
    success_url = reverse_lazy('volunteer')

volunteer.html

{% if messages %}
    <div class="alert center block" role="alert">
        <ul class="messages">
            {% for message in messages %}
            <li class="text-center"{% if message.tags %} class="{{ message.tags }}"{% endif %}>{{ message }}</li>
            {% endfor %}
        </ul>
    </div>
{% endif %}.....

但是不显示该消息 . 我可以在重定向的URL中看到请求标头上的消息json但不显示 . 请求标头的一部分

Cookie:olfsk=olfsk1757071755791586; hblid=HecPjm2lDQ2xTzgn3m39N0J00JEB6o1A; sessionid=z8zh4t13mw655mf3yn1vfnow8y58zxt9; csrftoken=GZxsdPZmBsefPU0nv7ZEfEaxsnPCMjIehpiFihY3GtTrhFnuFc5c3NXplD35Qslw; ext_name=jaehkpjddfdgiiefcnhahapilbejohhj;  
 messages="ab8f5c6976dd0939d4f1b867ca564577ba9cc0d7$[[\"__json_message\"\0540\05425\054\"Thank you!\"]]"

可能是没有显示消息的原因 . 有什么我想念的吗？