Python Web Frameworks by Carlos de la Guardia

Author:Carlos de la Guardia
Language: eng
Format: epub, mobi, pdf
Publisher: O'Reilly Media, Inc.
Published: 2016-02-29T05:00:00+00:00

Request handlers

class BaseHandler(tornado.web.RequestHandler): def get_current_user(self): return self.get_secure_cookie("user") class MainHandler(BaseHandler): def get(self): if not self.current_user: self.redirect("/login") return name = tornado.escape.xhtml_escape(self.current_user) self.render("hello.html", title="Welcome", name) class LoginHandler(BaseHandler): def get(self): self.render("login.html", title="Login Form") def post(self): self.set_secure_cookie("user", self.get_argument("name")) self.redirect("/") application = tornado.web.Application([ (r"/", MainHandler), (r"/login", LoginHandler)], cookie_secret="__TODO:_GENERATE_A_RANDOM_VALUE_HERE__")

Since request handlers are classes, you can use inheritance to define a base request handler that can have all the basic behavior needed for your application. In BaseHandler in the previous example, the get_current_user call will be available for both handlers defined in the next example.

A handler should have a method for every HTTP method that it can handle. In MainHandler, the GET method gets a look at the current user and redirects to the login handler if it is not set (remember that get_current_user is inherited from the base handler). If there’s a user, its name is escaped before being passed to the template. The render method of a handler gets a template by name, optionally passes it some arguments, and renders it.

LoginHandler has both GET and POST methods. The first renders the login form, and the second sets a secure cookie with the name and redirects to the MainHandler. The Tornado handlers have several utility methods to help with requests. For example, the self.get_argument method gets a parameter from the request. The request itself can be accessed with self.request.

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