A WSGI middleware component is a Python callable that is itself a WSGI application, but may handle requests by delegating to other WSGI applications. These applications can themselves be WSGI middleware components.
A middleware component can perform such functions as :
* Routing a request to different application objects based on the target URL, after changing the environment variables accordingly.
* Allowing multiple applications or frameworks to run side-by-side in the same process
* Load balancing and remote processing, by forwarding requests and responses over a network
* Performing content post-processing, such as applying XSLT stylesheets
