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DEPRECATION NOTICE

This version of Oz is deprecated. Much of the functionality has been supplanted both by improvements in tornado itself and in its surrounding ecosystem.

For a modern rehash, please see the new oz.

about

Oz is a set of classes for augmenting the functionality of the Tornado web framework. I will give you an e-high-five if you understand the name's reference.

django-style error messages

DjangoErrorMixin provides pretty Django-like error messages when an exception occurs. This is very useful when you're developing your web app, but not a good idea to run in production. Consequently, this tool only runs when the setting 'debug' is set to True.

To use it, first enable debug in the settings:

settings = {
    'debug': True,
}

app = tornado.web.Application([
    (r'/', HelloWorldHandler),
], **settings)

http_server = tornado.httpserver.HTTPServer(app)
http_server.listen(options.port)
tornado.ioloop.IOLoop.instance().start()

Then in your handler, add the mixin:

class HelloWorldHandler(DjangoErrorMixin, RequestHandler):
    def get(self):
        #This will throw an AssertionError to display the pretty error page
        assert False
        
        self.write('hello, world!')

If your application also defines a 'output_type_override' setting, the setting's value will be used as a parameter key that clients can use to change the error output format. For example, if you set 'output_type_override' to 'error_output', then a client upon making a request can set a GET or POST parameter error_output to either 'txt', 'verbose_txt' or 'html' to change the error output formatting. For example, a request to http://localhost:8080/?error_output=verbose_txt will provide a textual version of the Django error page instead. This is useful if you want the debugging richness of the Django error page, but your client cannot view html appropriately. Setting the format to txt will provide a simple Python stack trace. verbose_txt is roughly a textual equivalent of the Django error page. html is the default Dango error page output.

http basic authentication

BasicAuthMixin enables HTTP basic authentication. The tool is very flexible, as it uses a callback to check the credentials.

Add the mixin in your handler and call self.get_authenticated_user() (similar to the auth mixins provided by Tornado) when you want to authenticate the request:

class HelloWorldHandler(BasicAuthMixin, RequestHandler):
    def get(self):
        if not self.get_authenticated_user(auth_callback, 'realm'):
            return False
        
        self.write('hello, world!')

The first argument for get_authenticated_user() is the callback method you wish to use for authentication. The second argument is the realm. An example callback method:

def auth_callback(request, realm, username, password):
    if username == 'foo' and password == 'bar':
        request.user_id = 1
        return True
    else:
        return False

The method must a boolean stating whether the authentication succeeded. It takes in the RequestHandler object as the first argument in case you want to add some useful attributes (in this case, we're adding user_id).

If authentication fails, the RequestHandler will finish() and no further code will be executed. If it succeeds, the authenticated user will be available via RequestHandler.get_current_user().

You can also use the basic_auth decorator for methods that you wish to protect as an alternate use case for the mixin. Example:

class HelloWorldHandler(BasicAuthMixin, RequestHandler):
    @basic_auth(auth_callback, 'realm')
    def get(self):
        self.write('hello, world!')

This is equivalent to the previous implementation example.

argument patch

ArgumentPatchMixin replaces the default implementation of RequestHandler.get_argument(), which returns GET/POST parameters sent with the request. If a required argument is missing, it throws an HTTP code 400 (bad request) instead of a 404 (not found). I think this makes more sense.

To use it, all you have to do is add the mixin:

class HelloWorldHandler(ArgumentPatchMixin, RequestHandler):
    def get(self):
        name = self.get_argument('name')
        self.write('hello, %s!' % name)

notes

  • Always put the mixins before the RequestHandler on the inheritance list. This will work:

    class HelloWorldHandler(ArgumentPatchMixin, RequestHandler):
    ...

    Whereas this will NOT work:

    class HelloWorldHandler(RequestHandler, ArgumentPatchMixin):
    ...

  • You can mix and match multiple mixins. This will work fine:

    class HelloWorldHandler(BasicAuthMixin, DjangoErrorMixin,
    ArgumentPatchMixin, RequestHandler):
    ...