# Copyright 2015 The Tornado Authors
#
# 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
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# 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.
"""Flexible routing implementation.
Tornado routes HTTP requests to appropriate handlers using `Router`
class implementations. The `tornado.web.Application` class is a
`Router` implementation and may be used directly, or the classes in
this module may be used for additional flexibility. The `RuleRouter`
class can match on more criteria than `.Application`, or the `Router`
interface can be subclassed for maximum customization.
`Router` interface extends `~.httputil.HTTPServerConnectionDelegate`
to provide additional routing capabilities. This also means that any
`Router` implementation can be used directly as a ``request_callback``
for `~.httpserver.HTTPServer` constructor.
`Router` subclass must implement a ``find_handler`` method to provide
a suitable `~.httputil.HTTPMessageDelegate` instance to handle the
request:
.. code-block:: python
class CustomRouter(Router):
def find_handler(self, request, **kwargs):
# some routing logic providing a suitable HTTPMessageDelegate instance
return MessageDelegate(request.connection)
class MessageDelegate(HTTPMessageDelegate):
def __init__(self, connection):
self.connection = connection
def finish(self):
self.connection.write_headers(
ResponseStartLine("HTTP/1.1", 200, "OK"),
HTTPHeaders({"Content-Length": "2"}),
b"OK")
self.connection.finish()
router = CustomRouter()
server = HTTPServer(router)
The main responsibility of `Router` implementation is to provide a
mapping from a request to `~.httputil.HTTPMessageDelegate` instance
that will handle this request. In the example above we can see that
routing is possible even without instantiating an `~.web.Application`.
For routing to `~.web.RequestHandler` implementations we need an
`~.web.Application` instance. `~.web.Application.get_handler_delegate`
provides a convenient way to create `~.httputil.HTTPMessageDelegate`
for a given request and `~.web.RequestHandler`.
Here is a simple example of how we can we route to
`~.web.RequestHandler` subclasses by HTTP method:
.. code-block:: python
resources = {}
class GetResource(RequestHandler):
def get(self, path):
if path not in resources:
raise HTTPError(404)
self.finish(resources[path])
class PostResource(RequestHandler):
def post(self, path):
resources[path] = self.request.body
class HTTPMethodRouter(Router):
def __init__(self, app):
self.app = app
def find_handler(self, request, **kwargs):
handler = GetResource if request.method == "GET" else PostResource
return self.app.get_handler_delegate(request, handler, path_args=[request.path])
router = HTTPMethodRouter(Application())
server = HTTPServer(router)
`ReversibleRouter` interface adds the ability to distinguish between
the routes and reverse them to the original urls using route's name
and additional arguments. `~.web.Application` is itself an
implementation of `ReversibleRouter` class.
`RuleRouter` and `ReversibleRuleRouter` are implementations of
`Router` and `ReversibleRouter` interfaces and can be used for
creating rule-based routing configurations.
Rules are instances of `Rule` class. They contain a `Matcher`, which
provides the logic for determining whether the rule is a match for a
particular request and a target, which can be one of the following.
1) An instance of `~.httputil.HTTPServerConnectionDelegate`:
.. code-block:: python
router = RuleRouter([
Rule(PathMatches("/handler"), ConnectionDelegate()),
# ... more rules
])
class ConnectionDelegate(HTTPServerConnectionDelegate):
def start_request(self, server_conn, request_conn):
return MessageDelegate(request_conn)
2) A callable accepting a single argument of `~.httputil.HTTPServerRequest` type:
.. code-block:: python
router = RuleRouter([
Rule(PathMatches("/callable"), request_callable)
])
def request_callable(request):
request.write(b"HTTP/1.1 200 OK\\r\\nContent-Length: 2\\r\\n\\r\\nOK")
request.finish()
3) Another `Router` instance:
.. code-block:: python
router = RuleRouter([
Rule(PathMatches("/router.*"), CustomRouter())
])
Of course a nested `RuleRouter` or a `~.web.Application` is allowed:
.. code-block:: python
router = RuleRouter([
Rule(HostMatches("example.com"), RuleRouter([
Rule(PathMatches("/app1/.*"), Application([(r"/app1/handler", Handler)]))),
]))
])
server = HTTPServer(router)
In the example below `RuleRouter` is used to route between applications:
.. code-block:: python
app1 = Application([
(r"/app1/handler", Handler1),
# other handlers ...
])
app2 = Application([
(r"/app2/handler", Handler2),
# other handlers ...
])
router = RuleRouter([
Rule(PathMatches("/app1.*"), app1),
Rule(PathMatches("/app2.*"), app2)
])
server = HTTPServer(router)
For more information on application-level routing see docs for `~.web.Application`.
.. versionadded:: 4.5
"""
from __future__ import absolute_import, division, print_function
import re
from functools import partial
from tornado import httputil
from tornado.httpserver import _CallableAdapter
from tornado.escape import url_escape, url_unescape, utf8
from tornado.log import app_log
from tornado.util import basestring_type, import_object, re_unescape, unicode_type
try:
import typing # noqa
except ImportError:
pass
class Router(httputil.HTTPServerConnectionDelegate):
"""Abstract router interface."""
def find_handler(self, request, **kwargs):
# type: (httputil.HTTPServerRequest, typing.Any)->httputil.HTTPMessageDelegate
"""Must be implemented to return an appropriate instance of `~.httputil.HTTPMessageDelegate`
that can serve the request.
Routing implementations may pass additional kwargs to extend the routing logic.
:arg httputil.HTTPServerRequest request: current HTTP request.
:arg kwargs: additional keyword arguments passed by routing implementation.
:returns: an instance of `~.httputil.HTTPMessageDelegate` that will be used to
process the request.
"""
raise NotImplementedError()
def start_request(self, server_conn, request_conn):
return _RoutingDelegate(self, server_conn, request_conn)
class ReversibleRouter(Router):
"""Abstract router interface for routers that can handle named routes
and support reversing them to original urls.
"""
def reverse_url(self, name, *args):
"""Returns url string for a given route name and arguments
or ``None`` if no match is found.
:arg str name: route name.
:arg args: url parameters.
:returns: parametrized url string for a given route name (or ``None``).
"""
raise NotImplementedError()
class _RoutingDelegate(httputil.HTTPMessageDelegate):
def __init__(self, router, server_conn, request_conn):
self.server_conn = server_conn
self.request_conn = request_conn
self.delegate = None
self.router = router # type: Router
def headers_received(self, start_line, headers):
request = httputil.HTTPServerRequest(
connection=self.request_conn,
server_connection=self.server_conn,
start_line=start_line, headers=headers)
self.delegate = self.router.find_handler(request)
if self.delegate is None:
app_log.debug("Delegate for %s %s request not found",
start_line.method, start_line.path)
self.delegate = _DefaultMessageDelegate(self.request_conn)
return self.delegate.headers_received(start_line, headers)
def data_received(self, chunk):
return self.delegate.data_received(chunk)
def finish(self):
self.delegate.finish()
def on_connection_close(self):
self.delegate.on_connection_close()
class _DefaultMessageDelegate(httputil.HTTPMessageDelegate):
def __init__(self, connection):
self.connection = connection
def finish(self):
self.connection.write_headers(
httputil.ResponseStartLine("HTTP/1.1", 404, "Not Found"), httputil.HTTPHeaders())
self.connection.finish()
class RuleRouter(Router):
"""Rule-based router implementation."""
def __init__(self, rules=None):
"""Constructs a router from an ordered list of rules::
RuleRouter([
Rule(PathMatches("/handler"), Target),
# ... more rules
])
You can also omit explicit `Rule` constructor and use tuples of arguments::
RuleRouter([
(PathMatches("/handler"), Target),
])
`PathMatches` is a default matcher, so the example above can be simplified::
RuleRouter([
("/handler", Target),
])
In the examples above, ``Target`` can be a nested `Router` instance, an instance of
`~.httputil.HTTPServerConnectionDelegate` or an old-style callable,
accepting a request argument.
:arg rules: a list of `Rule` instances or tuples of `Rule`
constructor arguments.
"""
self.rules = [] # type: typing.List[Rule]
if rules:
self.add_rules(rules)
def add_rules(self, rules):
"""Appends new rules to the router.
:arg rules: a list of Rule instances (or tuples of arguments, which are
passed to Rule constructor).
"""
for rule in rules:
if isinstance(rule, (tuple, list)):
assert len(rule) in (2, 3, 4)
if isinstance(rule[0], basestring_type):
rule = Rule(PathMatches(rule[0]), *rule[1:])
else:
rule = Rule(*rule)
self.rules.append(self.process_rule(rule))
def process_rule(self, rule):
"""Override this method for additional preprocessing of each rule.
:arg Rule rule: a rule to be processed.
:returns: the same or modified Rule instance.
"""
return rule
def find_handler(self, request, **kwargs):
for rule in self.rules:
target_params = rule.matcher.match(request)
if target_params is not None:
if rule.target_kwargs:
target_params['target_kwargs'] = rule.target_kwargs
delegate = self.get_target_delegate(
rule.target, request, **target_params)
if delegate is not None:
return delegate
return None
def get_target_delegate(self, target, request, **target_params):
"""Returns an instance of `~.httputil.HTTPMessageDelegate` for a
Rule's target. This method is called by `~.find_handler` and can be
extended to provide additional target types.
:arg target: a Rule's target.
:arg httputil.HTTPServerRequest request: current request.
:arg target_params: additional parameters that can be useful
for `~.httputil.HTTPMessageDelegate` creation.
"""
if isinstance(target, Router):
return target.find_handler(request, **target_params)
elif isinstance(target, httputil.HTTPServerConnectionDelegate):
return target.start_request(request.server_connection, request.connection)
elif callable(target):
return _CallableAdapter(
partial(target, **target_params), request.connection
)
return None
class ReversibleRuleRouter(ReversibleRouter, RuleRouter):
"""A rule-based router that implements ``reverse_url`` method.
Each rule added to this router may have a ``name`` attribute that can be
used to reconstruct an original uri. The actual reconstruction takes place
in a rule's matcher (see `Matcher.reverse`).
"""
def __init__(self, rules=None):
self.named_rules = {} # type: typing.Dict[str]
super(ReversibleRuleRouter, self).__init__(rules)
def process_rule(self, rule):
rule = super(ReversibleRuleRouter, self).process_rule(rule)
if rule.name:
if rule.name in self.named_rules:
app_log.warning(
"Multiple handlers named %s; replacing previous value",
rule.name)
self.named_rules[rule.name] = rule
return rule
def reverse_url(self, name, *args):
if name in self.named_rules:
return self.named_rules[name].matcher.reverse(*args)
for rule in self.rules:
if isinstance(rule.target, ReversibleRouter):
reversed_url = rule.target.reverse_url(name, *args)
if reversed_url is not None:
return reversed_url
return None
class Rule(object):
"""A routing rule."""
def __init__(self, matcher, target, target_kwargs=None, name=None):
"""Constructs a Rule instance.
:arg Matcher matcher: a `Matcher` instance used for determining
whether the rule should be considered a match for a specific
request.
:arg target: a Rule's target (typically a ``RequestHandler`` or
`~.httputil.HTTPServerConnectionDelegate` subclass or even a nested `Router`,
depending on routing implementation).
:arg dict target_kwargs: a dict of parameters that can be useful
at the moment of target instantiation (for example, ``status_code``
for a ``RequestHandler`` subclass). They end up in
``target_params['target_kwargs']`` of `RuleRouter.get_target_delegate`
method.
:arg str name: the name of the rule that can be used to find it
in `ReversibleRouter.reverse_url` implementation.
"""
if isinstance(target, str):
# import the Module and instantiate the class
# Must be a fully qualified name (module.ClassName)
target = import_object(target)
self.matcher = matcher # type: Matcher
self.target = target
self.target_kwargs = target_kwargs if target_kwargs else {}
self.name = name
def reverse(self, *args):
return self.matcher.reverse(*args)
def __repr__(self):
return '%s(%r, %s, kwargs=%r, name=%r)' % \
(self.__class__.__name__, self.matcher,
self.target, self.target_kwargs, self.name)
class Matcher(object):
"""Represents a matcher for request features."""
def match(self, request):
"""Matches current instance against the request.
:arg httputil.HTTPServerRequest request: current HTTP request
:returns: a dict of parameters to be passed to the target handler
(for example, ``handler_kwargs``, ``path_args``, ``path_kwargs``
can be passed for proper `~.web.RequestHandler` instantiation).
An empty dict is a valid (and common) return value to indicate a match
when the argument-passing features are not used.
``None`` must be returned to indicate that there is no match."""
raise NotImplementedError()
def reverse(self, *args):
"""Reconstructs full url from matcher instance and additional arguments."""
return None
class AnyMatches(Matcher):
"""Matches any request."""
def match(self, request):
return {}
class HostMatches(Matcher):
"""Matches requests from hosts specified by ``host_pattern`` regex."""
def __init__(self, host_pattern):
if isinstance(host_pattern, basestring_type):
if not host_pattern.endswith("$"):
host_pattern += "$"
self.host_pattern = re.compile(host_pattern)
else:
self.host_pattern = host_pattern
def match(self, request):
if self.host_pattern.match(request.host_name):
return {}
return None
class DefaultHostMatches(Matcher):
"""Matches requests from host that is equal to application's default_host.
Always returns no match if ``X-Real-Ip`` header is present.
"""
def __init__(self, application, host_pattern):
self.application = application
self.host_pattern = host_pattern
def match(self, request):
# Look for default host if not behind load balancer (for debugging)
if "X-Real-Ip" not in request.headers:
if self.host_pattern.match(self.application.default_host):
return {}
return None
class PathMatches(Matcher):
"""Matches requests with paths specified by ``path_pattern`` regex."""
def __init__(self, path_pattern):
if isinstance(path_pattern, basestring_type):
if not path_pattern.endswith('$'):
path_pattern += '$'
self.regex = re.compile(path_pattern)
else:
self.regex = path_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._path, self._group_count = self._find_groups()
def match(self, request):
match = self.regex.match(request.path)
if match is None:
return None
if not self.regex.groups:
return {}
path_args, path_kwargs = [], {}
# 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.
if self.regex.groupindex:
path_kwargs = dict(
(str(k), _unquote_or_none(v))
for (k, v) in match.groupdict().items())
else:
path_args = [_unquote_or_none(s) for s in match.groups()]
return dict(path_args=path_args, path_kwargs=path_kwargs)
def reverse(self, *args):
if self._path is None:
raise ValueError("Cannot reverse url regex " + self.regex.pattern)
assert len(args) == self._group_count, "required number of arguments " \
"not found"
if not len(args):
return self._path
converted_args = []
for a in args:
if not isinstance(a, (unicode_type, bytes)):
a = str(a)
converted_args.append(url_escape(utf8(a), plus=False))
return self._path % tuple(converted_args)
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:])
else:
try:
unescaped_fragment = re_unescape(fragment)
except ValueError:
# If we can't unescape part of it, we can't
# reverse this url.
return (None, None)
pieces.append(unescaped_fragment)
return ''.join(pieces), self.regex.groups
class URLSpec(Rule):
"""Specifies mappings between URLs and handlers.
.. versionchanged: 4.5
`URLSpec` is now a subclass of a `Rule` with `PathMatches` matcher and is preserved for
backwards compatibility.
"""
def __init__(self, pattern, handler, kwargs=None, name=None):
"""Parameters:
* ``pattern``: Regular expression to be matched. Any capturing
groups in the regex will be passed in to the handler's
get/post/etc methods as arguments (by keyword if named, by
position if unnamed. Named and unnamed capturing groups
may not be mixed in the same rule).
* ``handler``: `~.web.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
`~.web.Application.reverse_url`.
"""
super(URLSpec, self).__init__(PathMatches(pattern), handler, kwargs, name)
self.regex = self.matcher.regex
self.handler_class = self.target
self.kwargs = kwargs
def __repr__(self):
return '%s(%r, %s, kwargs=%r, name=%r)' % \
(self.__class__.__name__, self.regex.pattern,
self.handler_class, self.kwargs, self.name)
def _unquote_or_none(s):
"""None-safe wrapper around url_unescape to handle unmatched optional
groups correctly.
Note that args are passed as bytes so the handler can decide what
encoding to use.
"""
if s is None:
return s
return url_unescape(s, encoding=None, plus=False)