Middleware that lets you test a response against a custom mapper object to programatically determine whether to internally forward to another URL and if so, which URL to forward to.

If you don't need the full power of this middleware you might choose to use the simpler forward middleware instead.

The arguments are:

app

The WSGI application or middleware chain.

mapper

A callable that takes a status code as the first parameter, a message as the second, and accepts optional environ, global_conf and named argments afterwards. It should return a URL to forward to or None if the code is not to be intercepted.

global_conf

Optional default configuration from your config file. If debug is set to true a message will be written to wsgi.errors on each internal forward stating the URL forwarded to.

**params

Optional, any other configuration and extra arguments you wish to pass which will in turn be passed back to the custom mapper object.

Here is an example where a 404 File Not Found status response would be redirected to the URL /error?code=404&message=File%20Not%20Found. This could be useful for passing the status code and message into another application to display an error document:

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from paste.errordocument import StatusBasedForward
from paste.recursive import RecursiveMiddleware
from urllib import urlencode

def error_mapper(code, message, environ, global_conf, kw)
    if code in [404, 500]:
        params = urlencode({'message':message, 'code':code})
        url = '/error?'%(params)
        return url
    else:
        return None

app = RecursiveMiddleware(
    StatusBasedForward(app, mapper=error_mapper),
)

This class contains 2 members.