Django切换MongoDB后启动服务器遇'module'不可调用错误求助

问题背景 #

将Django项目的数据库从SQLite切换为MongoDB，已执行以下命令：

python manage.py makemigrations
python manage.py migrate 

执行后无异常，但运行python manage.py runserver启动服务器时出现错误。

错误信息 #

System check identified no issues (0 silenced).
September 25, 2022 - 18:48:03
Django version 4.0.4, using settings 'passmanager.settings'
Starting development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.
Exception in thread django-main-thread:
Traceback (most recent call last):
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\threading.py", line 932, in _bootstrap_inner
    self.run()
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\utils\autoreload.py", line 64, in wrapper
    fn(*args, **kwargs)
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\core\management\commands\runserver.py", line 157, in inner_run
    handler = self.get_handler(*args, **options)
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\contrib\staticfiles\management\commands\runserver.py", line 31, in get_handler        
    handler = super().get_handler(*args, **options)
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\core\management\commands\runserver.py", line 78, in get_handler
    return get_internal_wsgi_application()
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\core\servers\basehttp.py", line 47, in get_internal_wsgi_application
    return import_string(app_path)
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\utils\module_loading.py", line 30, in import_string
    return cached_import(module_path, class_name)
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\utils\module_loading.py", line 15, in cached_import
    import_module(module_path)
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
  File "<frozen importlib._bootstrap>", line 991, in _find_and_load
  File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 783, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "E:\projects\pass-manager\password-manager\app\passmanager\wsgi.py", line 16, in <module>
    application = get_wsgi_application()
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\core\wsgi.py", line 13, in get_wsgi_application
    return WSGIHandler()
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\core\handlers\wsgi.py", line 126, in __init__
    self.load_middleware()
  File "C:\Users\Ashutosh Anand\AppData\Local\Programs\Python\Python38\lib\site-packages\django\core\handlers\base.py", line 61, in load_middleware
    mw_instance = middleware(adapted_handler)
TypeError: 'module' object is not callable

配置文件（settings.py）相关内容 #

# ... 其他配置省略 ...

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

# ... 其他配置省略 ...

DATABASES = {
        'default': {
            'ENGINE': 'djongo',
            'NAME': 'PasswordManager',
            'ENFORCE_SCHEMA': False,
            'CLIENT': {
                'host': 'mongodb+srv://loopassembly:<removed!>@cluster0.cwtfb.mongodb.net/test'
            }  
        }
}

问题原因 #

错误根源在MIDDLEWARE配置中，你错误地将INSTALLED_APPS里的应用模块（比如django.contrib.admin、django.contrib.auth等）添加到了中间件列表里。中间件列表需要的是可调用的中间件类路径，而不是应用模块，这些应用模块本身不是可调用的类，所以启动时会抛出'module' object is not callable错误。

解决方案 #

修改settings.py中的MIDDLEWARE配置，移除那些不属于中间件的应用模块，保留正确的中间件路径：

MIDDLEWARE = [
    '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',
]

修改完成后，重新运行python manage.py runserver即可正常启动服务器。

注：若需要其他文件信息，可补充说明。

内容的提问来源于stack exchange，提问作者loopassembly