# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
"""
WSGI middleware
Processes Python exceptions that relate to HTTP exceptions. This
defines a set of extensions, all subclasses of HTTPException, and a
middleware (`middleware`) that catches these exceptions and turns them
into proper responses.
"""
import types
class HTTPException(Exception):
code = None
title = None
message = None
# @@: not currently used:
required_headers = ()
def __init__(self, message=None, headers=None):
self.headers = headers
if message is not None:
self.message = message
Exception.__init__(self, self.message)
def html(self, environ):
message = self.message
args = environ.copy()
if self.headers:
environ.update(self.headers)
message = message % args
return ('%(title)s\n'
'\n'
'%(title)s
\n'
'%(message)s
\n'
'
\n'
'WSGI server
\n'
'\n'
% {'title': self.title,
'code': self.code,
'message': message})
def __repr__(self):
return '<%s %s; code=%s>' % (self.__class__.__name__,
self.title, self.code)
class _HTTPMove(HTTPException):
required_headers = ('location',)
message = ('The resource has been moved to '
'%(location)s; you should be redirected automatically.')
class HTTPMovedPermanently(_HTTPMove):
code = 301
title = 'Moved Permanently'
class HTTPFound(_HTTPMove):
code = 302
title = 'Found'
# This one is safe after a POST (the redirected location will be
# retrieved with GET):
class HTTPSeeOther(_HTTPMove):
code = 303
title = 'See Other'
class HTTPNotModified(HTTPException):
# @@: but not always (HTTP section 14.18.1)...?
required_headers = ('date',)
code = 304
title = 'Not Modified'
message = ''
# @@: should include date header, optionally other headers
class HTTPUserProxy(_HTTPMove):
# @@: OK, not a move, but looks a little like one
code = 305
title = 'Use Proxy'
message = ('This resource must be accessed through the proxy located '
'at %(location)s')
class HTTPTemporaryRedirect(_HTTPMove):
code = 307
title = 'Temporary Redirect'
class HTTPBadRequest(HTTPException):
code = 400
title = 'Bad Request'
message = ('The server could not understand your request')
class HTTPUnauthorized(HTTPException):
required_headers = ('WWW-Authenticate',)
code = 401
title = 'Unauthorized'
# @@: should require WWW-Authenticate header
message = ('Authorization is required to access this resource; '
'you must login.')
class HTTPForbidden(HTTPException):
code = 403
title = 'Forbidden'
message = ('Access was denied to this resource.')
class HTTPNotFound(HTTPException):
code = 404
title = 'Not Found'
message = ('The resource could not be found.')
class HTTPMethodNotAllowed(HTTPException):
required_headers = ('allowed',)
code = 405
title = 'Method Not Allowed'
message = ('The method %(REQUEST_METHOD)s is not allowed for this '
'resource.')
class HTTPNotAcceptable(HTTPException):
code = 406
title = 'Not Acceptable'
message = ('The resource could not be generated that was acceptable '
'to your browser (content of type %(HTTP_ACCEPT)s).')
class HTTPConfict(HTTPException):
code = 409
title = 'Conflict'
message = ('There was a conflict when trying to complete your '
'request.')
class HTTPGone(HTTPException):
code = 410
title = 'Gone'
message = ('This resource is no longer available. No forwarding '
'address is aavailable.')
class HTTPLengthRequired(HTTPException):
code = 411
title = 'Length Required'
message = ('Content-Length header required.')
class HTTPPreconditionFailed(HTTPException):
code = 412
title = 'Precondition Failed'
message = ('Request precondition failed.')
class HTTPRequestEntityTooLarge(HTTPException):
code = 413
title = 'Request Entity Too Large'
message = ('The body of your request was too large for this server.')
class HTTPRequestURITooLong(HTTPException):
code = 414
title = 'Request-URI Too Long'
message = ('The request URI was too long for this server.')
class HTTPUnsupportedMediaType(HTTPException):
code = 415
title = 'Unsupported Media Type'
message = ('The request media type %(CONTENT_TYPE)s is not '
'supported by this server.')
class HTTPRequestRangeNotSatisfiable(HTTPException):
code = 416
title = 'Request Range Not Satisfiable'
message = ('The Range requested is not available.')
class HTTPExpectationFailed(HTTPException):
code = 417
title = 'Expectation Failed'
message = ('Expectation failed.')
class HTTPServerError(HTTPException):
code = 500
title = 'Internal Server Error'
message = ('An internal server error occurred.')
class HTTPNotImplemented(HTTPException):
coded = 501
title = 'Not Implemented'
message = ('The request method %(REQUEST_METHOD)s is not implemented '
'for this server.')
class HTTPBadGateway(HTTPException):
code = 502
title = 'Bad Gateway'
message = ('Bad gateway.')
class HTTPServiceUnavailable(HTTPException):
code = 503
title = 'Service Unavailable'
message = ('The server is currently unavailable. Please try again '
'at a later time.')
class HTTPGatewayTimeout(HTTPException):
code = 504
title = 'Gateway Timeout'
message = ('The gateway has timed out.')
class HTTPHttpVersionNotSupported(HTTPException):
code = 505
title = 'HTTP Version Not Supported'
message = ('The HTTP version is not supported.')
__all__ = []
_exceptions = {}
for name, value in globals().items():
if (isinstance(value, (type, types.ClassType)) and
issubclass(value, HTTPException) and
value.code):
_exceptions[value.code] = value
__all__.append(name)
def get_exception(code):
return _exceptions[code]
############################################################
## Middleware implementation:
############################################################
def middleware(application, global_conf=None):
"""
This middleware catches any exceptions (which are subclasses of
`HTTPException`) and turns them into proper HTTP responses.
"""
def start_application(environ, start_response):
app_started = []
def checked_start_response(status, headers, exc_info=None):
app_started.append(None)
return start_response(status, headers, exc_info)
try:
return application(environ, checked_start_response)
except HTTPException, e:
if app_started:
# They've already started the response, so we can't
# do the right thing anymore.
raise
headers = {'content-type': 'text/html'}
if e.headers:
headers.update(e.headers)
start_response('%s %s' % (e.code, e.title),
headers.items())
return [e.html(environ)]
return start_application
__all__.extend(['middleware', 'get_exception'])