CODEWITHSUNDEEP
pythontornado
NetRocks
NetRocks

Reputation: 477

Error Handling in Tornado

I'm new to Tornado and writing a basic application but also need to add Error handling. Below is the code.

import tornado.httpserver
import tornado.ioloop
import tornado.options
import tornado.web

from tornado import gen
from tornado.web import asynchronous
from tornado.options import define, options

define("port", default=8888, help="run on the given port", type=int)

class Application(tornado.web.Application):
    def __init__(self):
        handlers = [
            (r"/", HomeHandler),
            (r"/mycompany", myCustomHandler),
            (r"/mycompany/", myCustomHandler),
        ]
        super(Application, self).__init__(handlers)

class HomeHandler(tornado.web.RequestHandler):
        def get(self):
                self.render("home.html")

class myCustom(tornado.web.RequestHandler):
        def get(self):
                self.write("Processing....")
                self.clear()
                self.finish()

def main():
    tornado.options.parse_command_line()
    http_server = tornado.httpserver.HTTPServer(Application())
    http_server.listen(options.port)
    tornado.ioloop.IOLoop.current().start()

if __name__ == "__main__":
    main()

The home.html works fine.

Next, I would like users to pass parameters using format something like http://host:port/mycompany/?id=9999.

But want to display a 404 PAGE when somebody enters *host:port/blahblah or *host:port/mycompany/?something=9999. How do I go about doing that? Thanks.

Upvotes: 1

Views: 2328

Answers (1)

Ben Darnell
Ben Darnell

Reputation: 22134

To use a custom error page for unknown URLs, use the default_handler_class argument to Application(). Errors raised within a handler use the write_error method to produce error pages. Using the same error handling for both is a little complicated; here's the basic scaffolding:

class BaseHandler(tornado.web.RequestHandler):
    def write_error(self, status_code, **kwargs):
        if status_code == 404:
            self.render("404.html")
        else:
            self.render("error.html")

class My404Handler(BaseHandler):
    def prepare(self):
        raise tornado.web.HTTPError(404)

class MyCustomHandler(BaseHandler):
    def get(self):
        if not self.valid_arguments():
            raise tornado.web.HTTPError(400)

app = Application([...], default_handler_class=My404Handler)

Upvotes: 1

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