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# coding: utf-8
# Copyright 2010 Alexandre Fiori
# based on the original Tornado by Facebook
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
The cyclone web framework looks a bit like ( or
Google's webapp (,
but with additional tools and optimizations to take advantage of the
non-blocking web server and tools.
Here is the canonical "Hello, world" example app::
import cyclone.web
from twisted.internet import reactor
class MainHandler(cyclone.web.RequestHandler):
def get(self):
self.write("Hello, world")
if __name__ == "__main__":
application = cyclone.web.Application([
(r"/", MainHandler),
reactor.listenTCP(8888, application)
See the cyclone walkthrough on for more details and a good
getting started guide.
Thread-safety notes
In general, methods on RequestHandler and elsewhere in cyclone are not
thread-safe. In particular, methods such as write(), finish(), and
flush() must only be called from the main thread. For more information on
using threads, please check the twisted documentation:
from __future__ import absolute_import, division, with_statement
import Cookie
import base64
import binascii
import calendar
import datetime
import email.utils
import functools
import gzip
import hashlib
import hmac
import httplib
import itertools
import mimetypes
import numbers
import os.path
import re
import stat
import sys
import threading
import time
import traceback
import types
import urllib
import urlparse
import uuid
import cyclone
from cyclone import escape
from cyclone import httpserver
from cyclone import locale
from cyclone import template
from cyclone.escape import utf8, _unicode
from cyclone.util import ObjectDict
from cyclone.util import bytes_type
from cyclone.util import import_object
from cyclone.util import unicode_type
from cStringIO import StringIO as BytesIO # python 2
from twisted.python import failure
from twisted.python import log
from twisted.internet import defer
from twisted.internet import protocol
from twisted.internet import reactor
class RequestHandler(object):
"""Subclass this class and define get() or post() to make a handler.
If you want to support more methods than the standard GET/HEAD/POST, you
should override the class variable SUPPORTED_METHODS in your
RequestHandler class.
If you want lists to be serialized when calling self.write() set
serialize_lists to True.
This may have some security implications if you are not protecting against
XSRF with other means (such as a XSRF token).
More details on this vulnerability here:
serialize_lists = False
no_keep_alive = False
xsrf_cookie_name = "_xsrf"
_template_loaders = {} # {path: template.BaseLoader}
_template_loader_lock = threading.Lock()
def __init__(self, application, request, **kwargs):
super(RequestHandler, self).__init__()
self.application = application
self.request = request
self._headers_written = False
self._finished = False
self._auto_finish = True
self._transforms = None # will be set in _execute
self.path_args = None
self.path_kwargs = None
self.ui = ObjectDict((n, self._ui_method(m)) for n, m in
# UIModules are available as both `modules` and `_modules` in the
# template namespace. Historically only `modules` was available
# but could be clobbered by user additions to the namespace.
# The template {% module %} directive looks in `_modules` to avoid
# possible conflicts.
self.ui["_modules"] = ObjectDict((n, self._ui_module(n, m)) for n, m in
self.ui["modules"] = self.ui["_modules"]
self.request.connection.no_keep_alive = self.no_keep_alive
def initialize(self, **kwargs):
"""Hook for subclass initialization.
A dictionary passed as the third argument of a url spec will be
supplied as keyword arguments to initialize().
class ProfileHandler(RequestHandler):
def initialize(self, database):
self.database = database
def get(self, username):
app = Application([
(r'/user/(.*)', ProfileHandler, dict(database=database)),
def settings(self):
"""An alias for `self.application.settings`."""
return self.application.settings
def default(self, *args, **kwargs):
"""Called when a request does not match any implemented methods.
class ExampleHandler(RequestHandler):
def get(self):
self.write('That was a GET request!')
def default(self):
self.write('That was anything but a GET request!')
raise HTTPError(405)
def prepare(self):
"""Called at the beginning of a request before `get`/`post`/etc.
Override this method to perform common initialization regardless
of the request method.
def on_finish(self):
"""Called after the end of a request.
Override this method to perform cleanup, logging, etc.
This method is a counterpart to `prepare`. ``on_finish`` may
not produce any output, as it is called after the response
has been sent to the client.
def on_connection_close(self, *args, **kwargs):
"""Called in async handlers if the client closed the connection.
Override this to clean up resources associated with
long-lived connections. Note that this method is called only if
the connection was closed during asynchronous processing; if you
need to do cleanup after every request override `on_finish`
Proxies may keep a connection open for a time (perhaps
indefinitely) after the client has gone away, so this method
may not be called promptly after the end user closes their
def clear(self):
"""Resets all headers and content for this response."""
# The performance cost of cyclone.httputil.HTTPHeaders is significant
# (slowing down a benchmark with a trivial handler by more than 10%),
# and its case-normalization is not generally necessary for
# headers we generate on the server side, so use a plain dict
# and list instead.
self._headers = {
"Server": "cyclone/%s" % cyclone.version,
"Content-Type": "text/html; charset=UTF-8",
"Date": datetime.datetime.utcnow().strftime(
"%a, %d %b %Y %H:%M:%S GMT"),
self._list_headers = []
if not self.request.supports_http_1_1():
if self.request.headers.get("Connection") == "Keep-Alive":
self.set_header("Connection", "Keep-Alive")
self._write_buffer = []
self._status_code = 200
self._reason = httplib.responses[200]
def set_default_headers(self):
"""Override this to set HTTP headers at the beginning of the request.
For example, this is the place to set a custom ``Server`` header.
Note that setting such headers in the normal flow of request
processing may not do what you want, since headers may be reset
during error handling.
def set_status(self, status_code, reason=None):
"""Sets the status code for our response.
:arg int status_code: Response status code. If `reason` is ``None``,
it must be present in `httplib.responses`.
:arg string reason: Human-readable reason phrase describing the status
code. If ``None``, it will be filled in from `httplib.responses`.
self._status_code = status_code
if reason is not None:
self._reason = escape.native_str(reason)
self._reason = httplib.responses[status_code]
except KeyError:
raise ValueError("unknown status code %d", status_code)
def get_status(self):
"""Returns the status code for our response."""
return self._status_code
def set_header(self, name, value):
"""Sets the given response header name and value.
If a datetime is given, we automatically format it according to the
HTTP specification. If the value is not a string, we convert it to
a string. All header values are then encoded as UTF-8.
self._headers[name] = self._convert_header_value(value)
def add_header(self, name, value):
"""Adds the given response header and value.
Unlike `set_header`, `add_header` may be called multiple times
to return multiple values for the same header.
self._list_headers.append((name, self._convert_header_value(value)))
def clear_header(self, name):
"""Clears an outgoing header, undoing a previous `set_header` call.
Note that this method does not apply to multi-valued headers
set by `add_header`.
if name in self._headers:
del self._headers[name]
def _convert_header_value(self, value):
if isinstance(value, bytes_type):
elif isinstance(value, unicode_type):
value = value.encode("utf-8")
elif isinstance(value, numbers.Integral):
# return immediately since we know the converted value will be safe
return str(value)
elif isinstance(value, datetime.datetime):
t = calendar.timegm(value.utctimetuple())
return email.utils.formatdate(t, localtime=False, usegmt=True)
raise TypeError("Unsupported header value %r" % value)
# If \n is allowed into the header, it is possible to inject
# additional headers or split the request. Also cap length to
# prevent obviously erroneous values.
if len(value) > 4000 or"[\x00-\x1f]", value):
raise ValueError("Unsafe header value %r", value)
return value
def get_argument(self, name, default=_ARG_DEFAULT, strip=True):
"""Returns the value of the argument with the given name.
If default is not provided, the argument is considered to be
required, and we throw an HTTP 400 exception if it is missing.
If the argument appears in the url more than once, we return the
last value.
The returned value is always unicode.
args = self.get_arguments(name, strip=strip)
if not args:
if default is self._ARG_DEFAULT:
raise HTTPError(400, "Missing argument " + name)
return default
return args[-1]
def get_arguments(self, name, strip=True):
"""Returns a list of the arguments with the given name.
If the argument is not present, returns an empty list.
The returned values are always unicode.
values = []
for v in self.request.arguments.get(name, []):
v = self.decode_argument(v, name=name)
if isinstance(v, unicode_type):
# Get rid of any weird control chars (unless decoding gave
# us bytes, in which case leave it alone)
v = re.sub(r"[\x00-\x08\x0e-\x1f]", " ", v)
if strip:
v = v.strip()
return values
def decode_argument(self, value, name=None):
"""Decodes an argument from the request.
The argument has been percent-decoded and is now a byte string.
By default, this method decodes the argument as utf-8 and returns
a unicode string, but this may be overridden in subclasses.
This method is used as a filter for both get_argument() and for
values extracted from the url and passed to get()/post()/etc.
The name of the argument is provided if known, but may be None
(e.g. for unnamed groups in the url regex).
return _unicode(value)
def cookies(self):
return self.request.cookies
def get_cookie(self, name, default=None):
"""Gets the value of the cookie with the given name, else default."""
if self.request.cookies is not None and name in self.request.cookies:
return self.request.cookies[name].value
return default
def set_cookie(self, name, value, domain=None, expires=None, path="/",
expires_days=None, **kwargs):
"""Sets the given cookie name/value with the given options.
Additional keyword arguments are set on the Cookie.Morsel directly.
for available attributes.
# The cookie library only accepts type str, in both python 2 and 3
name = escape.native_str(name)
value = escape.native_str(value)
if"[\x00-\x20]", name + value):
# Don't let us accidentally inject bad stuff
raise ValueError("Invalid cookie %r: %r" % (name, value))
if not hasattr(self, "_new_cookie"):
self._new_cookie = Cookie.SimpleCookie()
if name in self._new_cookie:
del self._new_cookie[name]
self._new_cookie[name] = value
morsel = self._new_cookie[name]
if domain:
morsel["domain"] = domain
if expires_days is not None and not expires:
expires = datetime.datetime.utcnow() + datetime.timedelta(
if expires:
timestamp = calendar.timegm(expires.utctimetuple())
morsel["expires"] = email.utils.formatdate(
timestamp, localtime=False, usegmt=True)
if path:
morsel["path"] = path
for k, v in kwargs.items():
if k == 'max_age':
k = 'max-age'
morsel[k] = v
def clear_cookie(self, name, path="/", domain=None):
"""Deletes the cookie with the given name."""
expires = datetime.datetime.utcnow() - datetime.timedelta(days=365)
self.set_cookie(name, value="", path=path, expires=expires,
def clear_all_cookies(self):
"""Deletes all the cookies the user sent with this request."""
for name in self.request.cookies.iterkeys():
def set_secure_cookie(self, name, value, expires_days=30, **kwargs):
"""Signs and timestamps a cookie so it cannot be forged.
You must specify the ``cookie_secret`` setting in your Application
to use this method. It should be a long, random sequence of bytes
to be used as the HMAC secret for the signature.
To read a cookie set with this method, use `get_secure_cookie()`.
Note that the ``expires_days`` parameter sets the lifetime of the
cookie in the browser, but is independent of the ``max_age_days``
parameter to `get_secure_cookie`.
Secure cookies may contain arbitrary byte values, not just unicode
strings (unlike regular cookies)
self.set_cookie(name, self.create_signed_value(name, value),
expires_days=expires_days, **kwargs)
def create_signed_value(self, name, value):
"""Signs and timestamps a string so it cannot be forged.
Normally used via set_secure_cookie, but provided as a separate
method for non-cookie uses. To decode a value not stored
as a cookie use the optional value argument to get_secure_cookie.
self.require_setting("cookie_secret", "secure cookies")
return create_signed_value(self.application.settings["cookie_secret"],
name, value)
def get_secure_cookie(self, name, value=None, max_age_days=31):
"""Returns the given signed cookie if it validates, or None.
The decoded cookie value is returned as a byte string (unlike
self.require_setting("cookie_secret", "secure cookies")
if value is None:
value = self.get_cookie(name)
return decode_signed_value(self.application.settings["cookie_secret"],
name, value, max_age_days=max_age_days)
def redirect(self, url, permanent=False, status=None):
"""Sends a redirect to the given (optionally relative) URL.
If the ``status`` argument is specified, that value is used as the
HTTP status code; otherwise either 301 (permanent) or 302
(temporary) is chosen based on the ``permanent`` argument.
The default is 302 (temporary).
if self._headers_written:
raise Exception("Cannot redirect after headers have been written")
if status is None:
status = 301 if permanent else 302
assert isinstance(status, types.IntType) and 300 <= status <= 399
# Remove whitespace
url = re.sub(r"[\x00-\x20]+", "", utf8(url))
if not self.request.uri.startswith('/'):
request_uri = ''
if self.request.uri.startswith('//'):
request_uri = ''
request_uri = self.request.uri
self.set_header("Location", urlparse.urljoin(utf8(request_uri),
def write(self, chunk):
"""Writes the given chunk to the output buffer.
To write the output to the network, use the flush() method below.
If the given chunk is a dictionary, we write it as JSON and set
the Content-Type of the response to be application/json.
(if you want to send JSON as a different Content-Type, call
set_header *after* calling write()).
Note that lists are not converted to JSON because of a potential
cross-site security vulnerability. All JSON output should be
wrapped in a dictionary. More details at\
if self._finished:
raise RuntimeError("Cannot write() after finish(). May be caused "
"by using async operations without the "
"@asynchronous decorator.")
if isinstance(chunk, types.DictType) or \
(self.serialize_lists and isinstance(chunk, types.ListType)):
chunk = escape.json_encode(chunk)
self.set_header("Content-Type", "application/json")
chunk = utf8(chunk)
def render(self, template_name, **kwargs):
"""Renders the template with the given arguments as the response."""
d = defer.maybeDeferred(self.render_string, template_name, **kwargs)
d.addCallbacks(self.finish, self._execute_failure)
return d
def _insertAdditionalPageElements(self, html): # pragma: no cover
"""Insert the additional JS and CSS added by the modules on the page"""
js_embed = []
js_files = []
css_embed = []
css_files = []
html_heads = []
html_bodies = []
for module in getattr(self, "_active_modules", {}).values():
embed_part = module.embedded_javascript()
if embed_part:
file_part = module.javascript_files()
if file_part:
if isinstance(file_part, (unicode_type, bytes_type)):
embed_part = module.embedded_css()
if embed_part:
file_part = module.css_files()
if file_part:
if isinstance(file_part, (unicode_type, bytes_type)):
head_part = module.html_head()
if head_part:
body_part = module.html_body()
if body_part:
def is_absolute(path):
return any(path.startswith(x) for x in ["/", "http:", "https:"])
if js_files:
# Maintain order of JavaScript files given by modules
paths = []
unique_paths = set()
for path in js_files:
if not is_absolute(path):
path = self.static_url(path)
if path not in unique_paths:
js = ''.join('<script src="' + escape.xhtml_escape(p) +
'" type="text/javascript"></script>'
for p in paths)
sloc = html.rindex('</body>')
html = html[:sloc] + utf8(js) + '\n' + html[sloc:]
if js_embed:
js = '<script type="text/javascript">\n//<![CDATA[\n' + \
'\n'.join(js_embed) + '\n//]]>\n</script>'
sloc = html.rindex('</body>')
html = html[:sloc] + js + '\n' + html[sloc:]
if css_files:
paths = []
unique_paths = set()
for path in css_files:
if not is_absolute(path):
path = self.static_url(path)
if path not in unique_paths:
css = ''.join('<link href="' + escape.xhtml_escape(p) + '" '
'type="text/css" rel="stylesheet"/>'
for p in paths)
hloc = html.index('</head>')
html = html[:hloc] + utf8(css) + '\n' + html[hloc:]
if css_embed:
css = '<style type="text/css">\n' + '\n'.join(css_embed) + \
hloc = html.index('</head>')
html = html[:hloc] + css + '\n' + html[hloc:]
if html_heads:
hloc = html.index('</head>')
html = html[:hloc] + ''.join(html_heads) + '\n' + html[hloc:]
if html_bodies:
hloc = html.index('</body>')
html = html[:hloc] + ''.join(html_bodies) + '\n' + html[hloc:]
return html
def render_string(self, template_name, **kwargs):
"""Generate the given template with the given arguments.
We return the generated string. To generate and write a template
as a response, use render() above.
# If no template_path is specified, use the path of the calling file
template_path = self.get_template_path()
if not template_path:
frame = sys._getframe(0)
web_file = frame.f_code.co_filename
while frame.f_code.co_filename == web_file:
frame = frame.f_back
template_path = os.path.dirname(frame.f_code.co_filename)
with RequestHandler._template_loader_lock:
if template_path not in RequestHandler._template_loaders:
loader = self.create_template_loader(template_path)
RequestHandler._template_loaders[template_path] = loader
loader = RequestHandler._template_loaders[template_path]
t = loader.load(template_name)
namespace = self.get_template_namespace()
return t.generate(**namespace)
def get_template_namespace(self):
"""Returns a dictionary to be used as the default template namespace.
May be overridden by subclasses to add or modify values.
The results of this method will be combined with additional
defaults in the `tornado.template` module and keyword arguments
to `render` or `render_string`.
namespace = dict(
return namespace
def create_template_loader(self, template_path):
"""Returns a new template loader for the given path.
May be overridden by subclasses. By default returns a
directory-based loader on the given path, using the
``autoescape`` application setting. If a ``template_loader``
application setting is supplied, uses that instead.
settings = self.application.settings
if "template_loader" in settings:
return settings["template_loader"]
kwargs = {}
if "autoescape" in settings:
# autoescape=None means "no escaping", so we have to be sure
# to only pass this kwarg if the user asked for it.
kwargs["autoescape"] = settings["autoescape"]
return template.Loader(template_path, **kwargs)
def flush(self, include_footers=False):
"""Flushes the current output buffer to the network."""
chunk = "".join(self._write_buffer)
self._write_buffer = []
if not self._headers_written:
self._headers_written = True
for transform in self._transforms:
self._status_code, self._headers, chunk = \
self._status_code, self._headers, chunk, include_footers)
headers = self._generate_headers()
for transform in self._transforms: # pragma: no cover
chunk = transform.transform_chunk(chunk, include_footers)
headers = ""
# Ignore the chunk and only write the headers for HEAD requests
if self.request.method == "HEAD":
if headers:
if headers or chunk:
self.request.write(headers + chunk)
def notifyFinish(self):
"""Returns a deferred, which is fired when the request is terminated
and the connection is closed.
return self.request.notifyFinish()
def finish(self, chunk=None):
"""Finishes this response, ending the HTTP request."""
if self._finished:
raise RuntimeError("finish() called twice. May be caused "
"by using async operations without the "
"@asynchronous decorator.")
if chunk is not None:
# Automatically support ETags and add the Content-Length header if
# we have not flushed any content yet.
if not self._headers_written:
if (self._status_code == 200 and
self.request.method in ("GET", "HEAD") and
"Etag" not in self._headers):
etag = self.compute_etag()
if etag is not None:
self.set_header("Etag", etag)
inm = self.request.headers.get("If-None-Match")
if inm and inm.find(etag) != -1:
self._write_buffer = []
if self._status_code == 304:
assert not self._write_buffer, "Cannot send body with 304"
elif "Content-Length" not in self._headers:
content_length = sum(len(part) for part in self._write_buffer)
self.set_header("Content-Length", content_length)
self._finished = True
def send_error(self, status_code=500, **kwargs):
"""Sends the given HTTP error code to the browser.
If `flush()` has already been called, it is not possible to send
an error, so this method will simply terminate the response.
If output has been written but not yet flushed, it will be discarded
and replaced with the error page.
Override `write_error()` to customize the error page that is returned.
Additional keyword arguments are passed through to `write_error`.
if self._headers_written:
log.msg("Cannot send error response after headers written")
if not self._finished:
reason = None
if "exc_info" in kwargs:
e = kwargs["exc_info"][1]
if isinstance(e, HTTPError) and e.reason:
reason = e.reason
elif "exception" in kwargs:
e = kwargs["exception"]
if isinstance(e, HTTPAuthenticationRequired):
args = ",".join(['%s="%s"' % (k, v)
for k, v in e.kwargs.items()])
self.set_header("WWW-Authenticate", "%s %s" %
(e.auth_type, args))
self.set_status(status_code, reason=reason)
self.write_error(status_code, **kwargs)
except Exception, e:
log.msg("Uncaught exception in write_error: " + str(e))
if not self._finished:
def write_error(self, status_code, **kwargs):
"""Override to implement custom error pages.
``write_error`` may call `write`, `render`, `set_header`, etc
to produce output as usual.
If this error was caused by an uncaught exception (including
HTTPError), an ``exc_info`` triple will be available as
``kwargs["exc_info"]``. Note that this exception may not be
the "current" exception for purposes of methods like
``sys.exc_info()`` or ``traceback.format_exc``.
For historical reasons, if a method ``get_error_html`` exists,
it will be used instead of the default ``write_error`` implementation.
``get_error_html`` returned a string instead of producing output
normally, and had different semantics for exception handling.
Users of ``get_error_html`` are encouraged to convert their code
to override ``write_error`` instead.
In order for error pages to be generated for paths that do not match any
handlers, you can use the `error_handler` keyword argument when
instantiating the ``cyclone.web.Application`` object.
For example::
import cyclone.web
import httplib
class CustomErrorPageMixin(object):
def write_error(self, status_code, **kwargs**):
kwargs["code"] = status_code
if 'message' not in kwargs:
kwargs["message"] = httplib.responses[status_code]
self.render("error_%d.html" % status_code, fields=kwargs)
except IOError:
self.render("error_all.html", fields=kwargs)
class CustomErrorHandler(CustomErrorPageMixin, cyclone.web.ErrorHandler):
class BaseHandler(CustomErrorPageMixin, cyclone.web.RequestHandler):
Then, when constructing the ``cyclone.web.Application`` object::
from cyclone import web
application = web.Application([
(r"/", MainPageHandler),
], error_handler=CustomErrorHandler)
This technique is also compatible with Bottle-style applications::
from cyclone.bottle import create_app
# create_app takes the same arguments as run
application = create_app(base_handler=BaseHandler,
if hasattr(self, 'get_error_html'):
if 'exc_info' in kwargs:
exc_info = kwargs.pop('exc_info')
kwargs['exception'] = exc_info[1]
# Put the traceback into sys.exc_info()
raise exc_info[0], exc_info[1], exc_info[2]
except Exception:
self.finish(self.get_error_html(status_code, **kwargs))
self.finish(self.get_error_html(status_code, **kwargs))
if self.settings.get("debug") and "exc_info" in kwargs:
# in debug mode, try to send a traceback
self.set_header('Content-Type', 'text/plain')
for line in traceback.format_exception(*kwargs["exc_info"]):
self.finish("<html><title>%(code)d: %(message)s</title>"
"<body>%(code)d: %(message)s</body></html>" %
{"code": status_code, "message": self._reason})
def locale(self):
"""The local for the current session.
Determined by either get_user_locale, which you can override to
set the locale based on, e.g., a user preference stored in a
database, or get_browser_locale, which uses the Accept-Language
if not hasattr(self, "_locale"):
self._locale = self.get_user_locale()
if not self._locale:
self._locale = self.get_browser_locale()
assert self._locale
return self._locale
def get_user_locale(self):
"""Override to determine the locale from the authenticated user.
If None is returned, we fall back to get_browser_locale().
This method should return a cyclone.locale.Locale object,
most likely obtained via a call like cyclone.locale.get("en")
return None
def get_browser_locale(self, default="en_US"):
"""Determines the user's locale from Accept-Language header.
if "Accept-Language" in self.request.headers:
languages = self.request.headers["Accept-Language"].split(",")
locales = []
for language in languages:
parts = language.strip().split(";")
if len(parts) > 1 and parts[1].startswith("q="):
score = float(parts[1][2:])
except (ValueError, TypeError):
score = 0.0
score = 1.0
locales.append((parts[0], score))
if locales:
locales.sort(key=lambda pair: pair[1], reverse=True)
codes = [l[0] for l in locales]
return locale.get(*codes)
return locale.get(default)
def current_user(self):
"""The authenticated user for this request.
Determined by either get_current_user, which you can override to
set the user based on, e.g., a cookie. If that method is not
overridden, this method always returns None.
We lazy-load the current user the first time this method is called
and cache the result after that.
if not hasattr(self, "_current_user"):
self._current_user = self.get_current_user()
return self._current_user
def get_current_user(self):
"""Override to determine the current user from, e.g., a cookie."""
return None
def get_login_url(self):
"""Override to customize the login URL based on the request.
By default, we use the 'login_url' application setting.
self.require_setting("login_url", "@cyclone.web.authenticated")
return self.application.settings["login_url"]
def get_template_path(self):
"""Override to customize template path for each handler.
By default, we use the 'template_path' application setting.
Return None to load templates relative to the calling file.
return self.application.settings.get("template_path")
def xsrf_token(self):
"""The XSRF-prevention token for the current user/session.
To prevent cross-site request forgery, we set an '_xsrf' cookie
and include the same '_xsrf' value as an argument with all POST
requests. If the two do not match, we reject the form submission
as a potential forgery.
if not hasattr(self, "_xsrf_token"):
token = self.get_cookie(self.xsrf_cookie_name)
if not token:
token = binascii.b2a_hex(uuid.uuid4().bytes)
expires_days = 30 if self.current_user else None
self.set_cookie(self.xsrf_cookie_name, token, expires_days=expires_days)
self._xsrf_token = token
return self._xsrf_token
def check_xsrf_cookie(self):
"""Verifies that the '_xsrf' cookie matches the '_xsrf' argument.
To prevent cross-site request forgery, we set an '_xsrf'
cookie and include the same value as a non-cookie
field with all POST requests. If the two do not match, we
reject the form submission as a potential forgery.
The _xsrf value may be set as either a form field named _xsrf
or in a custom HTTP header named X-XSRFToken or X-CSRFToken
(the latter is accepted for compatibility with Django).
Prior to release 1.1.1, this check was ignored if the HTTP header
"X-Requested-With: XMLHTTPRequest" was present. This exception
has been shown to be insecure and has been removed. For more
information please see\
token = (self.get_argument(self.xsrf_cookie_name, None) or
self.request.headers.get("X-Xsrftoken") or
if not token:
raise HTTPError(403, "'_xsrf' argument missing from POST")
if self.xsrf_token != token:
raise HTTPError(403, "XSRF cookie does not match POST argument")
def xsrf_form_html(self):
"""An HTML <input/> element to be included with all POST forms.
It defines the _xsrf input value, which we check on all POST
requests to prevent cross-site request forgery. If you have set
the 'xsrf_cookies' application setting, you must include this
HTML within all of your HTML forms.
See check_xsrf_cookie() above for more information.
return '<input type="hidden" name="' + self.xsrf_cookie_name + \
'" value="' + escape.xhtml_escape(self.xsrf_token) + '"/>'
def static_url(self, path, include_host=None):
"""Returns a static URL for the given relative static file path.
This method requires you set the 'static_path' setting in your
application (which specifies the root directory of your static
We append ?v=<signature> to the returned URL, which makes our
static file handler set an infinite expiration header on the
returned content. The signature is based on the content of the
By default this method returns URLs relative to the current
host, but if ``include_host`` is true the URL returned will be
absolute. If this handler has an ``include_host`` attribute,
that value will be used as the default for all `static_url`
calls that do not pass ``include_host`` as a keyword argument.
self.require_setting("static_path", "static_url")
static_handler_class = self.settings.get(
"static_handler_class", StaticFileHandler)
if include_host is None:
include_host = getattr(self, "include_host", False)
if include_host:
base = self.request.protocol + "://" + + \
static_handler_class.make_static_url(self.settings, path)
base = static_handler_class.make_static_url(self.settings, path)
return base
def async_callback(self, callback, *args, **kwargs):
"""Obsolete - catches exceptions from the wrapped function.
This function is unnecessary since Tornado 1.1.
if callback is None:
return None
if args or kwargs:
callback = functools.partial(callback, *args, **kwargs)
def wrapper(*args, **kwargs):
return callback(*args, **kwargs)
except Exception, e:
if self._headers_written:
log.msg("Exception after headers written: " + e)
return wrapper
def require_setting(self, name, feature="this feature"):
"""Raises an exception if the given app setting is not defined."""
if not self.application.settings.get(name):
raise Exception("You must define the '%s' setting in your "
"application to use %s" % (name, feature))
def reverse_url(self, name, *args, **kwargs):
"""Alias for `Application.reverse_url`."""
return self.application.reverse_url(name, *args, **kwargs)
def compute_etag(self):
"""Computes the etag header to be used for this request.
May be overridden to provide custom etag implementations,
or may return None to disable cyclone's default etag support.
hasher = hashlib.sha1()
for part in self._write_buffer:
return '"' + hasher.hexdigest() + '"'
def _execute(self, transforms, *args, **kwargs):
"""Executes this request with the given output transforms."""
self._transforms = transforms
if self.request.method not in self.SUPPORTED_METHODS:
raise HTTPError(405)
self.path_args = [self.decode_argument(arg) for arg in args]
self.path_kwargs = dict((k, self.decode_argument(v, name=k))
for (k, v) in kwargs.items())
# If XSRF cookies are turned on, reject form submissions without
# the proper cookie
if self.request.method not in ("GET", "HEAD", "OPTIONS") and \
self.application.settings.get("xsrf_cookies"): # is True
if not getattr(self, "no_xsrf", False):
lambda f: self._handle_request_exception(f.value),
callbackArgs=(args, kwargs))
except Exception, e:
def _deferred_handler(self, function, *args, **kwargs):
result = function(*args, **kwargs)
if isinstance(result, defer.Deferred):
return result
elif isinstance(result, types.GeneratorType):
# This may degrade performance a bit, but at least avoid the
# server from breaking when someone call yield without
# decorating their handler with @inlineCallbacks.
log.msg("[warning] %s.%s() returned a generator. "
"Perhaps it should be decorated with "
"@inlineCallbacks." % (self.__class__.__name__,
return self._deferred_handler(defer.inlineCallbacks(function),
*args, **kwargs)
elif isinstance(result, failure.Failure):
return defer.succeed(result)
def _execute_handler(self, r, args, kwargs):
if not self._finished:
args = [self.decode_argument(arg) for arg in args]
kwargs = dict((k, self.decode_argument(v, name=k))
for (k, v) in kwargs.iteritems())
function = getattr(self, self.request.method.lower(), self.default)
d = self._deferred_handler(function, *args, **kwargs)
d.addCallbacks(self._execute_success, self._execute_failure)
def _execute_success(self, ign):
if self._auto_finish and not self._finished:
return self.finish()
def _execute_failure(self, err):
return self._handle_request_exception(err)
def _generate_headers(self):
reason = self._reason
lines = [utf8(self.request.version + " " +
str(self._status_code) +
" " + reason)]
lines.extend([(utf8(n) + ": " + utf8(v)) for n, v in
itertools.chain(self._headers.items(), self._list_headers)])
if hasattr(self, "_new_cookie"):
for cookie in self._new_cookie.values():
lines.append(utf8("Set-Cookie: " + cookie.OutputString(None)))
return "\r\n".join(lines) + "\r\n\r\n"
def _log(self):
"""Logs the current request.
Sort of deprecated since this functionality was moved to the
Application, but left in place for the benefit of existing apps
that have overridden this method.
def _request_summary(self):
return self.request.method + " " + self.request.uri + " (" + \
self.request.remote_ip + ")"
def _handle_request_exception(self, e):
# These are normally twisted.python.failure.Failure
if isinstance(e.value, (template.TemplateError,
HTTPError, HTTPAuthenticationRequired)):
e = e.value
if isinstance(e, template.TemplateError):
self.send_error(500, exception=e)
elif isinstance(e, (HTTPError, HTTPAuthenticationRequired)):
if e.log_message and self.settings.get("debug") is True:
if e.status_code not in httplib.responses:
log.msg("Bad HTTP status code: " + repr(e.status_code))
e.status_code = 500
self.send_error(e.status_code, exception=e)
log.msg("Uncaught exception\n" + str(e))
if self.settings.get("debug"):
self.send_error(500, exception=e)
def _ui_module(self, name, module):
def render(*args, **kwargs):
if not hasattr(self, "_active_modules"):
self._active_modules = {}
if name not in self._active_modules:
self._active_modules[name] = module(self)
rendered = self._active_modules[name].render(*args, **kwargs)
return rendered
return render
def _ui_method(self, method):
return lambda *args, **kwargs: method(self, *args, **kwargs)
def _clear_headers_for_304(self):
# 304 responses should not contain entity headers (defined in
# not explicitly allowed by
headers = ["Allow", "Content-Encoding", "Content-Language",
"Content-Length", "Content-MD5", "Content-Range",
"Content-Type", "Last-Modified"]
for h in headers:
def asynchronous(method):
"""Wrap request handler methods with this if they are asynchronous.
If this decorator is given, the response is not finished when the
method returns. It is up to the request handler to call self.finish()
to terminate the HTTP request. Without this decorator, the request is
automatically finished when the get() or post() method returns. ::
from twisted.internet import reactor
class MyRequestHandler(web.RequestHandler):
def get(self):
self.write("Processing your request...")
reactor.callLater(5, self.do_something)
def do_something(self):
It may be used for Comet and similar push techniques.
def wrapper(self, *args, **kwargs):
self._auto_finish = False
return method(self, *args, **kwargs)
return wrapper
def removeslash(method):
"""Use this decorator to remove trailing slashes from the request path.
For example, a request to ``'/foo/'`` would redirect to ``'/foo'`` with
this decorator. Your request handler mapping should use a regular
expression like ``r'/foo/*'`` in conjunction with using the decorator.
def wrapper(self, *args, **kwargs):
if self.request.path.endswith("/"):
if self.request.method in ("GET", "HEAD", "POST", "PUT", "DELETE"):
uri = self.request.path.rstrip("/")
if uri: # don't try to redirect '/' to ''
if self.request.query:
uri = uri + "?" + self.request.query
self.redirect(uri, permanent=True)
raise HTTPError(404)
return method(self, *args, **kwargs)
return wrapper
def addslash(method):
"""Use this decorator to add a missing trailing slash to the request path.
For example, a request to '/foo' would redirect to '/foo/' with this
decorator. Your request handler mapping should use a regular expression
like r'/foo/?' in conjunction with using the decorator.
def wrapper(self, *args, **kwargs):
if not self.request.path.endswith("/"):
if self.request.method in ("GET", "HEAD", "POST", "PUT", "DELETE"):
uri = self.request.path + "/"
if self.request.query:
uri = uri + "?" + self.request.query
self.redirect(uri, permanent=True)
raise HTTPError(404)
return method(self, *args, **kwargs)
return wrapper
class Application(protocol.ServerFactory):
"""A collection of request handlers that make up a web application.
Instances of this class are callable and can be passed directly to
HTTPServer to serve the application::
application = web.Application([
(r"/", MainPageHandler),
reactor.listenTCP(8888, application)
The constructor for this class takes in a list of URLSpec objects
or (regexp, request_class) tuples. When we receive requests, we
iterate over the list in order and instantiate an instance of the
first request class whose regexp matches the request path.
Each tuple can contain an optional third element, which should be a
dictionary if it is present. That dictionary is passed as keyword
arguments to the contructor of the handler. This pattern is used
for the StaticFileHandler below (note that a StaticFileHandler
can be installed automatically with the static_path setting described
application = web.Application([
(r"/static/(.*)", web.StaticFileHandler, {"path": "/var/www"}),
We support virtual hosts with the add_handlers method, which takes in
a host regular expression as the first argument::
application.add_handlers(r"www\.myhost\.com", [
(r"/article/([0-9]+)", ArticleHandler),
You can serve static files by sending the static_path setting as a
keyword argument. We will serve those files from the /static/ URI
(this is configurable with the static_url_prefix setting),
and we will serve /favicon.ico and /robots.txt from the same directory.
A custom subclass of StaticFileHandler can be specified with the
static_handler_class setting.
It is also possible to customize the error pages the application generates
in case it does not find any handler for the incoming request by using the
`error_handler` keyword argument. This allows for consistent error pages
across the application.
.. attribute:: settings
Additonal keyword arguments passed to the constructor are saved in the
`settings` dictionary, and are often referred to in documentation as
"application settings".
protocol = httpserver.HTTPConnection
def __init__(self, handlers=None, default_host="",
transforms=None, error_handler=None, **settings):
if transforms is None:
self.transforms = []
if settings.get("gzip"):
self.transforms = transforms
self.handlers = []
self.named_handlers = {}
self.error_handler = error_handler or ErrorHandler
self.default_host = default_host
self.settings = ObjectDict(settings)
self.ui_modules = {"linkify": _linkify,
"xsrf_form_html": _xsrf_form_html,
"Template": TemplateModule}
self.ui_methods = {}
self._load_ui_modules(settings.get("ui_modules", {}))
self._load_ui_methods(settings.get("ui_methods", {}))
if "static_path" in self.settings:
path = self.settings["static_path"]
handlers = list(handlers or [])
static_url_prefix = settings.get("static_url_prefix",
static_handler_class = settings.get("static_handler_class",
static_handler_args = settings.get("static_handler_args", {})
static_handler_args["path"] = path
for pattern in [re.escape(static_url_prefix) + r"(.*)",
r"/(favicon\.ico)", r"/(robots\.txt)"]:
handlers.insert(0, (pattern, static_handler_class,
if handlers:
self.add_handlers(".*$", handlers)
def add_handlers(self, host_pattern, host_handlers):
"""Appends the given handlers to our handler list.
Host patterns are processed sequentially in the order they were
added. All matching patterns will be considered.
if not host_pattern.endswith("$"):
host_pattern += "$"
handlers = []
# The handlers with the wildcard host_pattern are a special
# case - they're added in the constructor but should have lower
# precedence than the more-precise handlers added later.
# If a wildcard handler group exists, it should always be last
# in the list, so insert new groups just before it.
if self.handlers and self.handlers[-1][0].pattern == '.*$':
self.handlers.insert(-1, (re.compile(host_pattern), handlers))
self.handlers.append((re.compile(host_pattern), handlers))
for spec in host_handlers:
if isinstance(spec, types.TupleType):
assert len(spec) in (2, 3)
pattern = spec[0]
handler = spec[1]
if isinstance(handler, types.StringType):
# import the Module and instantiate the class
# Must be a fully qualified name (module.ClassName)
handler = import_object(handler)
except ImportError, e:
"Unable to load handler '%s' for "
"'%s': %s" % (handler, pattern, e))
if len(spec) == 3:
kwargs = spec[2]
kwargs = {}
spec = URLSpec(pattern, handler, kwargs)
if in self.named_handlers:
log.msg("Multiple handlers named %s; "
"replacing previous value" %
self.named_handlers[] = spec
def add_transform(self, transform_class):
"""Adds the given OutputTransform to our transform list."""
def _get_host_handlers(self, request):
host =':')[0]
matches = []
for pattern, handlers in self.handlers:
if pattern.match(host):
# Look for default host if not behind load balancer (for debugging)
if not matches and "X-Real-Ip" not in request.headers:
for pattern, handlers in self.handlers:
if pattern.match(self.default_host):
return matches or None
def _load_ui_methods(self, methods):
if isinstance(methods, types.ModuleType):
self._load_ui_methods(dict((n, getattr(methods, n))
for n in dir(methods)))
elif isinstance(methods, types.ListType):
for m in methods:
for name, fn in methods.items():
if not name.startswith("_") and hasattr(fn, "__call__") \
and name[0].lower() == name[0]:
self.ui_methods[name] = fn
def _load_ui_modules(self, modules):
if isinstance(modules, types.ModuleType):
self._load_ui_modules(dict((n, getattr(modules, n))
for n in dir(modules)))
elif isinstance(modules, types.ListType):
for m in modules:
assert isinstance(modules, types.DictType)
for name, cls in modules.items():
if issubclass(cls, UIModule):
self.ui_modules[name] = cls
except TypeError:
def __call__(self, request):
"""Called by HTTPServer to execute the request."""
transforms = [t(request) for t in self.transforms]
handler = None
args = []
kwargs = {}
handlers = self._get_host_handlers(request)
if not handlers:
handler = RedirectHandler(self, request,
url="http://" + self.default_host + "/")
for spec in handlers:
match = spec.regex.match(request.path)
if match:
handler = spec.handler_class(self, request, **spec.kwargs)
if spec.regex.groups:
# None-safe wrapper around url_unescape to handle
# unmatched optional groups correctly
def unquote(s):
if s is None:
return s
return escape.url_unescape(s, encoding=None)
# Pass matched groups to the handler. Since
# match.groups() includes both named and
# unnamed groups,we want to use either groups
# or groupdict but not both.
# Note that args are passed as bytes so the handler can
# decide what encoding to use.
if spec.regex.groupindex:
kwargs = dict((str(k), unquote(v))
for (k, v) in match.groupdict().items())
args = [unquote(s) for s in match.groups()]
if not handler:
handler = self.error_handler(self, request, status_code=404)
# In debug mode, re-compile templates and reload static files on every
# request so you don't need to restart to see changes
if self.settings.get("debug"):
with RequestHandler._template_loader_lock:
for loader in RequestHandler._template_loaders.values():
handler._execute(transforms, *args, **kwargs)
return handler
def reverse_url(self, name, *args, **kwargs):
"""Returns a URL path for handler named `name`
The handler must be added to the application as a named URLSpec.
Args will be substituted for capturing groups in the URLSpec regex.
They will be converted to strings if necessary, encoded as utf8,
and url-escaped.
Kwargs will be urlencoded and passed as named parameters.
if name in self.named_handlers:
return self.named_handlers[name].reverse(*args, **kwargs)
raise KeyError("%s not found in named urls" % name)
def log_request(self, handler):
"""Writes a completed HTTP request to the logs.
By default writes to the python root logger. To change
this behavior either subclass Application and override this method,
or pass a function in the application settings dictionary as
if "log_function" in self.settings:
request_time = 1000.0 * handler.request.request_time()
log.msg("[" + handler.request.protocol + "] " +
str(handler.get_status()) + " " + handler._request_summary() +
" %.2fms" % request_time)
class HTTPError(Exception):
"""An exception that will turn into an HTTP error response.
:arg int status_code: HTTP status code. Must be listed in
`httplib.responses` unless the ``reason`` keyword argument is given.
:arg string log_message: Message to be written to the log for this error
(will not be shown to the user unless the `Application` is in debug
mode). May contain ``%s``-style placeholders, which will be filled
in with remaining positional parameters.
:arg string reason: Keyword-only argument. The HTTP "reason" phrase
to pass in the status line along with ``status_code``. Normally
determined automatically from ``status_code``, but can be used
to use a non-standard numeric code.
def __init__(self, status_code, log_message=None, *args, **kwargs):
self.status_code = status_code
self.log_message = log_message
self.args = args
self.reason = kwargs.get("reason", None)
def __str__(self):
if self.log_message:
return self.log_message % self.args
return self.reason or \
httplib.responses.get(self.status_code, "Unknown")
class HTTPAuthenticationRequired(HTTPError):
"""An exception that will turn into an HTTP 401, Authentication Required.
The arguments are used to compose the ``WWW-Authenticate`` header.
See for details.
:arg string auth_type: Authentication type (``Basic``, ``Digest``, etc)
:arg string realm: Realm (Usually displayed by the browser)
def __init__(self, log_message=None,
auth_type="Basic", realm="Restricted Access", **kwargs):
self.status_code = 401
self.log_message = log_message
self.auth_type = auth_type
self.kwargs = kwargs
self.kwargs["realm"] = realm
class ErrorHandler(RequestHandler):
"""Generates an error response with status_code for all requests."""
def initialize(self, status_code):
def prepare(self):
raise HTTPError(self._status_code)
def check_xsrf_cookie(self):
# POSTs to an ErrorHandler don't actually have side effects,
# so we don't need to check the xsrf token. This allows POSTs
# to the wrong url to return a 404 instead of 403.
class RedirectHandler(RequestHandler):
"""Redirects the client to the given URL for all GET requests.
You should provide the keyword argument "url" to the handler, e.g.::
application = web.Application([
(r"/oldpath", web.RedirectHandler, {"url": "/newpath"}),
def initialize(self, url, permanent=True):
self._url = url
self._permanent = permanent
def get(self):
self.redirect(self._url, permanent=self._permanent)
class StaticFileHandler(RequestHandler):
"""A simple handler that can serve static content from a directory.
To map a path to this handler for a static data directory /var/www,
you would add a line to your application like::
application = web.Application([
(r"/static/(.*)", web.StaticFileHandler, {"path": "/var/www"}),
The local root directory of the content should be passed as the "path"
argument to the handler.
To support aggressive browser caching, if the argument "v" is given
with the path, we set an infinite HTTP expiration header. So, if you
want browsers to cache a file indefinitely, send them to, e.g.,
/static/images/myimage.png?v=xxx. Override ``get_cache_time`` method for
more fine-grained cache control.
CACHE_MAX_AGE = 86400 * 365 * 10 # 10 years
_static_hashes = {}
_lock = threading.Lock() # protects _static_hashes
def initialize(self, path, default_filename=None):
self.root = "%s%s" % (os.path.abspath(path), os.path.sep)
self.default_filename = default_filename
def reset(cls):
with cls._lock:
cls._static_hashes = {}
def head(self, path):
self.get(path, include_body=False)
def get(self, path, include_body=True):
path = self.parse_url_path(path)
abspath = os.path.abspath(os.path.join(self.root, path))
# os.path.abspath strips a trailing /
# it needs to be temporarily added back for requests to root/
if not (abspath + os.path.sep).startswith(self.root):
raise HTTPError(403, "%s is not in root static directory", path)
if os.path.isdir(abspath) and self.default_filename is not None:
# need to look at the request.path here for when path is empty
# but there is some prefix to the path that was already
# trimmed by the routing
if not self.request.path.endswith("/"):
self.redirect("%s/" % self.request.path)
abspath = os.path.join(abspath, self.default_filename)
if not os.path.exists(abspath):
raise HTTPError(404)
if not os.path.isfile(abspath):
raise HTTPError(403, "%s is not a file", path)
stat_result = os.stat(abspath)
modified = datetime.datetime.fromtimestamp(stat_result[stat.ST_MTIME])
self.set_header("Last-Modified", modified)
mime_type, encoding = mimetypes.guess_type(abspath)
if mime_type:
self.set_header("Content-Type", mime_type)
cache_time = self.get_cache_time(path, modified, mime_type)
if cache_time > 0:
self.set_header("Expires", "%s" % (datetime.datetime.utcnow() +
self.set_header("Cache-Control", "max-age=%s" % str(cache_time))
# Check the If-Modified-Since, and don't send the result if the
# content has not been modified
ims_value = self.request.headers.get("If-Modified-Since")
if ims_value is not None:
date_tuple = email.utils.parsedate(ims_value)
if_since = datetime.datetime.fromtimestamp(time.mktime(date_tuple))
if if_since >= modified:
with open(abspath, "rb") as file:
data =
if include_body:
assert self.request.method == "HEAD"
self.set_header("Content-Length", len(data))
def set_extra_headers(self, path):
"""For subclass to add extra headers to the response"""
def get_cache_time(self, path, modified, mime_type):
"""Override to customize cache control behavior.
Return a positive number of seconds to trigger aggressive caching or 0
to mark resource as cacheable, only.
By default returns cache expiry of 10 years for resources requested
with "v" argument.
return self.CACHE_MAX_AGE if "v" in self.request.arguments else 0
def make_static_url(cls, settings, path):
"""Constructs a versioned url for the given path.
This method may be overridden in subclasses (but note that it is
a class method rather than an instance method).
``settings`` is the `Application.settings` dictionary. ``path``
is the static path being requested. The url returned should be
relative to the current host.
static_url_prefix = settings.get('static_url_prefix', '/static/')
version_hash = cls.get_version(settings, path)
if version_hash:
return "%s%s?v=%s" % (static_url_prefix, path, version_hash)
return "%s%s" % (static_url_prefix, path)
def get_version(cls, settings, path):
"""Generate the version string to be used in static URLs.
This method may be overridden in subclasses (but note that it
is a class method rather than a static method). The default
implementation uses a hash of the file's contents.
``settings`` is the `Application.settings` dictionary and ``path``
is the relative location of the requested asset on the filesystem.
The returned value should be a string, or ``None`` if no version
could be determined.
abs_path = os.path.join(settings["static_path"], path)
with cls._lock:
hashes = cls._static_hashes
if abs_path not in hashes:
f = open(abs_path, "rb")
hashes[abs_path] = hashlib.md5(
except Exception:
log.msg("Could not open static file %r" % path)
hashes[abs_path] = None
hsh = hashes.get(abs_path)
if hsh:
return hsh[:5]
return None
def parse_url_path(self, url_path):
"""Converts a static URL path into a filesystem path.
``url_path`` is the path component of the URL with
``static_url_prefix`` removed. The return value should be
filesystem path relative to ``static_path``.
if os.path.sep != "/":
url_path = url_path.replace("/", os.path.sep)
return url_path
class FallbackHandler(RequestHandler):
"""A RequestHandler that wraps another HTTP server callback.
Tornado has this to combine RequestHandlers and WSGI handlers, but it's
not supported in cyclone and is just here for compatibily purposes.
def initialize(self, fallback):
self.fallback = fallback
def prepare(self):
self._finished = True
class OutputTransform(object):
"""A transform modifies the result of an HTTP request (e.g., GZip encoding)
A new transform instance is created for every request. See the
ChunkedTransferEncoding example below if you want to implement a
new Transform.
def __init__(self, request):
def transform_first_chunk(self, status_code, headers, chunk, finishing):
return status_code, headers, chunk
def transform_chunk(self, chunk, finishing):
return chunk
class GZipContentEncoding(OutputTransform):
"""Applies the gzip content encoding to the response.
"text/plain", "text/html", "text/css", "text/xml",
"application/javascript", "application/x-javascript",
"application/xml", "application/atom+xml",
"text/javascript", "application/json", "application/xhtml+xml"])
def __init__(self, request):
self._gzipping = request.supports_http_1_1() and \
"gzip" in request.headers.get("Accept-Encoding", [])
def transform_first_chunk(self, status_code, headers, chunk, finishing):
if 'Vary' in headers:
headers['Vary'] += ', Accept-Encoding'
headers['Vary'] = 'Accept-Encoding'
if self._gzipping:
ctype = _unicode(headers.get("Content-Type", "")).split(";")[0]
self._gzipping = (ctype in self.CONTENT_TYPES) and \
(not finishing or len(chunk) >= self.MIN_LENGTH) and \
(finishing or "Content-Length" not in headers) and \
("Content-Encoding" not in headers)
if self._gzipping:
headers["Content-Encoding"] = "gzip"
self._gzip_value = BytesIO()
self._gzip_file = gzip.GzipFile(mode="w", fileobj=self._gzip_value)
chunk = self.transform_chunk(chunk, finishing)
if "Content-Length" in headers:
headers["Content-Length"] = str(len(chunk))
return status_code, headers, chunk
def transform_chunk(self, chunk, finishing):
if self._gzipping:
if finishing:
chunk = self._gzip_value.getvalue()
return chunk
class ChunkedTransferEncoding(OutputTransform):
"""Applies the chunked transfer encoding to the response.
def __init__(self, request):
self._chunking = request.supports_http_1_1()
def transform_first_chunk(self, status_code, headers, chunk, finishing):
# 304 responses have no body (not even a zero-length body), and so
# should not have either Content-Length or Transfer-Encoding headers.
if self._chunking and status_code != 304:
# No need to chunk the output if a Content-Length is specified
if "Content-Length" in headers or "Transfer-Encoding" in headers:
self._chunking = False
headers["Transfer-Encoding"] = "chunked"
chunk = self.transform_chunk(chunk, finishing)
return status_code, headers, chunk
def transform_chunk(self, block, finishing):
if self._chunking:
# Don't write out empty chunks because that means END-OF-STREAM
# with chunked encoding
if block:
block = "%s\r\n%s\r\n" % (utf8("%x" % len(block)), block)
if finishing:
block = "%s0\r\n\r\n" % block
return block
def authenticated(method):
"""Decorate methods with this to require that the user be logged in."""
def wrapper(self, *args, **kwargs):
if not self.current_user:
if self.request.method in ("GET", "HEAD"):
url = self.get_login_url()
if "?" not in url:
if urlparse.urlsplit(url).scheme:
# if login url is absolute, make next absolute too
next_url = self.request.full_url()
next_url = self.request.uri
url = "%s?%s" % (url,
return self.redirect(url)
raise HTTPError(403)
return method(self, *args, **kwargs)
return wrapper
class UIModule(object):
"""A UI re-usable, modular unit on a page.
UI modules often execute additional queries, and they can include
additional CSS and JavaScript that will be included in the output
page, which is automatically inserted on page render.
def __init__(self, handler):
self.handler = handler
self.request = handler.request
self.ui = handler.ui
self.current_user = handler.current_user
self.locale = handler.locale
def render(self, *args, **kwargs):
"""Overridden in subclasses to return this module's output."""
raise NotImplementedError()
def embedded_javascript(self):
"""Returns a JavaScript string that will be embedded in the page."""
return None
def javascript_files(self):
"""Returns a list of JavaScript files required by this module."""
return None
def embedded_css(self):
"""Returns a CSS string that will be embedded in the page."""
return None
def css_files(self):
"""Returns a list of CSS files required by this module."""
return None
def html_head(self):
"""Returns a CSS string that will be put in the <head/> element"""
return None
def html_body(self):
"""Returns an HTML string that will be put in the <body/> element"""
return None
def render_string(self, path, **kwargs):
"""Renders a template and returns it as a string."""
return self.handler.render_string(path, **kwargs)
class _linkify(UIModule):
def render(self, text, **kwargs):
return escape.linkify(text, **kwargs)
class _xsrf_form_html(UIModule):
def render(self):
return self.handler.xsrf_form_html()
class TemplateModule(UIModule):
"""UIModule that simply renders the given template.
{% module Template("foo.html") %} is similar to {% include "foo.html" %},
but the module version gets its own namespace (with kwargs passed to
Template()) instead of inheriting the outer template's namespace.
Templates rendered through this module also get access to UIModule's
automatic javascript/css features. Simply call set_resources
inside the template and give it keyword arguments corresponding to
the methods on UIModule: {{ set_resources(js_files=static_url("my.js")) }}
Note that these resources are output once per template file, not once
per instantiation of the template, so they must not depend on
any arguments to the template.
def __init__(self, handler):
super(TemplateModule, self).__init__(handler)
# keep resources in both a list and a dict to preserve order
self._resource_list = []
self._resource_dict = {}
def render(self, path, **kwargs):
def set_resources(**kwargs):
if path not in self._resource_dict:
self._resource_dict[path] = kwargs
if self._resource_dict[path] != kwargs:
raise ValueError("set_resources called with different "
"resources for the same template")
return ""
return self.render_string(path, set_resources=set_resources,
def _get_resources(self, key):
return (r[key] for r in self._resource_list if key in r)
def embedded_javascript(self):
return "\n".join(self._get_resources("embedded_javascript"))
def javascript_files(self):
result = []
for f in self._get_resources("javascript_files"):
if isinstance(f, (unicode, bytes_type)):
return result
def embedded_css(self):
return "\n".join(self._get_resources("embedded_css"))
def css_files(self):
result = []
for f in self._get_resources("css_files"):
if isinstance(f, (unicode, bytes_type)):
return result
def html_head(self):
return "".join(self._get_resources("html_head"))
def html_body(self):
return "".join(self._get_resources("html_body"))
class URLReverseError(Exception):
"""Error generating reversed URL."""
class URLSpec(object):
"""Specifies mappings between URLs and handlers."""
def __init__(self, pattern, handler_class, kwargs=None, name=None):
"""Creates a URLSpec.
pattern: Regular expression to be matched. Any groups in the regex
will be passed in to the handler's get/post/etc methods as
handler_class: RequestHandler subclass to be invoked.
kwargs (optional): A dictionary of additional arguments to be passed
to the handler's constructor.
name (optional): A name for this handler. Used by
if not pattern.endswith('$'):
pattern += '$'
self.regex = re.compile(pattern)
assert len(self.regex.groupindex) in (0, self.regex.groups), \
("groups in url regexes must either be all named or all "
"positional: %r" % self.regex.pattern)
self.handler_class = handler_class
self.kwargs = kwargs or {} = name
self._path, self._group_count = self._find_groups()
def __repr__(self):
return '%s(%r, %s, kwargs=%r, name=%r)' % \
(self.__class__.__name__, self.regex.pattern,
self.handler_class, self.kwargs,
def _find_groups(self):
"""Returns a tuple (reverse string, group count) for a url.
For example: Given the url pattern /([0-9]{4})/([a-z-]+)/, this method
would return ('/%s/%s/', 2).
pattern = self.regex.pattern
if pattern.startswith('^'):
pattern = pattern[1:]
if pattern.endswith('$'):
pattern = pattern[:-1]
if self.regex.groups != pattern.count('('):
# The pattern is too complicated for our simplistic matching,
# so we can't support reversing it.
return (None, None)
pieces = []
for fragment in pattern.split('('):
if ')' in fragment:
paren_loc = fragment.index(')')
if paren_loc >= 0:
pieces.append('%s' + fragment[paren_loc + 1:])
return (''.join(pieces), self.regex.groups)
def reverse(self, *args, **kwargs):
if not self._path:
raise URLReverseError(
"Cannot reverse url regex " + self.regex.pattern
if len(args) != self._group_count:
raise URLReverseError(
"required number of arguments not found"
rv = self._path
if args:
converted_args = []
for a in args:
if not isinstance(a, (unicode_type, bytes_type)):
a = str(a)
rv = rv % tuple(converted_args)
if kwargs:
items = list(kwargs.items())
items.sort(key=lambda el: el[0])
rv += "?" + urllib.urlencode(items)
return rv
url = URLSpec
def _time_independent_equals(a, b):
if len(a) != len(b):
return False
result = 0
if isinstance(a[0], types.IntType): # python3 byte strings
for x, y in zip(a, b):
result |= x ^ y
else: # python2
for x, y in zip(a, b):
result |= ord(x) ^ ord(y)
return result == 0
def create_signed_value(secret, name, value):
timestamp = utf8(str(int(time.time())))
value = base64.b64encode(utf8(value))
signature = _create_signature(secret, name, value, timestamp)
value = "|".join([value, timestamp, signature])
return value
def decode_signed_value(secret, name, value, max_age_days=31):
if not value:
return None
parts = utf8(value).split("|")
if len(parts) != 3:
return None
signature = _create_signature(secret, name, parts[0], parts[1])
if not _time_independent_equals(parts[2], signature):
log.msg("Invalid cookie signature %r" % value)
return None
timestamp = int(parts[1])
if timestamp < time.time() - max_age_days * 86400:
log.msg("Expired cookie %r" % value)
return None
if timestamp > time.time() + 31 * 86400:
# _cookie_signature does not hash a delimiter between the
# parts of the cookie, so an attacker could transfer trailing
# digits from the payload to the timestamp without altering the
# signature. For backwards compatibility, sanity-check timestamp
# here instead of modifying _cookie_signature.
log.msg("Cookie timestamp in future; possible tampering %r" % value)
return None
if parts[1].startswith("0"):
log.msg("Tampered cookie %r" % value)
return None
return base64.b64decode(parts[0])
except Exception:
return None
def _create_signature(secret, *parts):
hash =, digestmod=hashlib.sha1)
for part in parts:
return utf8(hash.hexdigest())
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