1Adding HTTP Method Overrides
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3
4Some HTTP proxies do not support arbitrary HTTP methods or newer HTTP
5methods (such as PATCH). In that case it's possible to "proxy" HTTP
6methods through another HTTP method in total violation of the protocol.
7
8The way this works is by letting the client do an HTTP POST request and
9set the ``X-HTTP-Method-Override`` header. Then the method is replaced
10with the header value before being passed to Flask.
11
12This can be accomplished with an HTTP middleware::
13
14    class HTTPMethodOverrideMiddleware(object):
15        allowed_methods = frozenset([
16            'GET',
17            'HEAD',
18            'POST',
19            'DELETE',
20            'PUT',
21            'PATCH',
22            'OPTIONS'
23        ])
24        bodyless_methods = frozenset(['GET', 'HEAD', 'OPTIONS', 'DELETE'])
25
26        def __init__(self, app):
27            self.app = app
28
29        def __call__(self, environ, start_response):
30            method = environ.get('HTTP_X_HTTP_METHOD_OVERRIDE', '').upper()
31            if method in self.allowed_methods:
32                environ['REQUEST_METHOD'] = method
33            if method in self.bodyless_methods:
34                environ['CONTENT_LENGTH'] = '0'
35            return self.app(environ, start_response)
36
37To use this with Flask, wrap the app object with the middleware::
38
39    from flask import Flask
40
41    app = Flask(__name__)
42    app.wsgi_app = HTTPMethodOverrideMiddleware(app.wsgi_app)
43