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# Middlewares

Middlewares wrap applications to dispatch between then or provide additional request handling. Additionally to the middlewares documented here, there is also the `DebuggedApplication` class that is implemented as a WSGI middleware.

class `werkzeug.wsgi.``SharedDataMiddleware`(app, exports, disallow=None, cache=True, cache_timeout=43200, fallback_mimetype='text/plain')

  A WSGI middleware that provides static content for development environments or simple server setups. Usage is quite simple:

      import os
      from werkzeug.wsgi import SharedDataMiddleware

      app = SharedDataMiddleware(app, {
          '/shared': os.path.join(os.path.dirname(__file__), 'shared')
      })

  The contents of the folder `./shared` will now be available on `http://example.com/shared/`. This is pretty useful during development because a standalone media server is not required. One can also mount files on the root folder and still continue to use the application because the shared data middleware forwards all unhandled requests to the application, even if the requests are below one of the shared folders.

  If pkg_resources is available you can also tell the middleware to serve files from package data:

      app = SharedDataMiddleware(app, {
          '/shared': ('myapplication', 'shared_files')
      })

  This will then serve the `shared_files` folder in the myapplication Python package.

  The optional disallow parameter can be a list of `fnmatch()` rules for files that are not accessible from the web. If cache is set to False no caching headers are sent.

  Currently the middleware does not support non ASCII filenames. If the encoding on the file system happens to be the encoding of the URI it may work but this could also be by accident. We strongly suggest using ASCII only file names for static files.

  The middleware will guess the mimetype using the Python mimetype module. If it’s unable to figure out the charset it will fall back to fallback_mimetype.

  Changed in version 0.5: The cache timeout is configurable now.

  New in version 0.6: The fallback_mimetype parameter was added.

  Parameters:

  - app – the application to wrap. If you don’t want to wrap an application you can pass it `NotFound`.
  - exports – a dict of exported files and folders.
  - disallow – a list of `fnmatch()` rules.
  - fallback_mimetype – the fallback mimetype for unknown files.
  - cache – enable or disable caching headers.

  Param cache_timeout:
  | the cache timeout in seconds for the headers.

  `is_allowed`(filename)

    Subclasses can override this method to disallow the access to certain files. However by providing disallow in the constructor this method is overwritten.

class `werkzeug.wsgi.``DispatcherMiddleware`(app, mounts=None)

  Allows one to mount middlewares or applications in a WSGI application. This is useful if you want to combine multiple WSGI applications:

      app = DispatcherMiddleware(app, {
          '/app2':        app2,
          '/app3':        app3
      })

Also there’s the …

`werkzeug._internal.``_easteregg`(app)

  Like the name says. But who knows how it works?