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| """ | |
| Application Dispatcher | |
| ====================== | |
| This middleware creates a single WSGI application that dispatches to | |
| multiple other WSGI applications mounted at different URL paths. | |
| A common example is writing a Single Page Application, where you have a | |
| backend API and a frontend written in JavaScript that does the routing | |
| in the browser rather than requesting different pages from the server. | |
| The frontend is a single HTML and JS file that should be served for any | |
| path besides "/api". | |
| This example dispatches to an API app under "/api", an admin app | |
| under "/admin", and an app that serves frontend files for all other | |
| requests:: | |
| app = DispatcherMiddleware(serve_frontend, { | |
| '/api': api_app, | |
| '/admin': admin_app, | |
| }) | |
| In production, you might instead handle this at the HTTP server level, | |
| serving files or proxying to application servers based on location. The | |
| API and admin apps would each be deployed with a separate WSGI server, | |
| and the static files would be served directly by the HTTP server. | |
| .. autoclass:: DispatcherMiddleware | |
| :copyright: 2007 Pallets | |
| :license: BSD-3-Clause | |
| """ | |
| from __future__ import annotations | |
| import typing as t | |
| if t.TYPE_CHECKING: | |
| from _typeshed.wsgi import StartResponse | |
| from _typeshed.wsgi import WSGIApplication | |
| from _typeshed.wsgi import WSGIEnvironment | |
| class DispatcherMiddleware: | |
| """Combine multiple applications as a single WSGI application. | |
| Requests are dispatched to an application based on the path it is | |
| mounted under. | |
| :param app: The WSGI application to dispatch to if the request | |
| doesn't match a mounted path. | |
| :param mounts: Maps path prefixes to applications for dispatching. | |
| """ | |
| def __init__( | |
| self, | |
| app: WSGIApplication, | |
| mounts: dict[str, WSGIApplication] | None = None, | |
| ) -> None: | |
| self.app = app | |
| self.mounts = mounts or {} | |
| def __call__( | |
| self, environ: WSGIEnvironment, start_response: StartResponse | |
| ) -> t.Iterable[bytes]: | |
| script = environ.get("PATH_INFO", "") | |
| path_info = "" | |
| while "/" in script: | |
| if script in self.mounts: | |
| app = self.mounts[script] | |
| break | |
| script, last_item = script.rsplit("/", 1) | |
| path_info = f"/{last_item}{path_info}" | |
| else: | |
| app = self.mounts.get(script, self.app) | |
| original_script_name = environ.get("SCRIPT_NAME", "") | |
| environ["SCRIPT_NAME"] = original_script_name + script | |
| environ["PATH_INFO"] = path_info | |
| return app(environ, start_response) | |