google_appengine/google/appengine/ext/webapp/util.py

   1 #!/usr/bin/env python
   2 #
   3 # Copyright 2007 Google Inc.
   4 #
   5 # Licensed under the Apache License, Version 2.0 (the "License");
   6 # you may not use this file except in compliance with the License.
   7 # You may obtain a copy of the License at
   8 #
   9 #     http://www.apache.org/licenses/LICENSE-2.0
  10 #
  11 # Unless required by applicable law or agreed to in writing, software
  12 # distributed under the License is distributed on an "AS IS" BASIS,
  13 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14 # See the License for the specific language governing permissions and
  15 # limitations under the License.
  16 #
  17
  18 """Convience functions for the Webapp framework."""
  19
  20
  21
  22
  23
  24 __all__ = ['login_required',
  25            'run_wsgi_app',
  26            'add_wsgi_middleware',
  27            'run_bare_wsgi_app',
  28            ]
  29
  30 import os
  31 import sys
  32 import wsgiref.util
  33
  34 from google.appengine.api import users
  35 from google.appengine.api import lib_config
  36 from google.appengine.ext import webapp
  37
  38
  39 def login_required(handler_method):
  40   """A decorator to require that a user be logged in to access a handler.
  41
  42   To use it, decorate your get() method like this:
  43
  44     @login_required
  45     def get(self):
  46       user = users.get_current_user(self)
  47       self.response.out.write('Hello, ' + user.nickname())
  48
  49   We will redirect to a login page if the user is not logged in. We always
  50   redirect to the request URI, and Google Accounts only redirects back as a GET
  51   request, so this should not be used for POSTs.
  52   """
  53   def check_login(self, *args):
  54     if self.request.method != 'GET':
  55       raise webapp.Error('The check_login decorator can only be used for GET '
  56                          'requests')
  57     user = users.get_current_user()
  58     if not user:
  59       self.redirect(users.create_login_url(self.request.uri))
  60       return
  61     else:
  62       handler_method(self, *args)
  63   return check_login
  64
  65
  66 _config_handle = lib_config.register(
  67     'webapp',
  68     {'add_wsgi_middleware': lambda app: app})
  69
  70
  71 def run_wsgi_app(application):
  72   """Runs your WSGI-compliant application object in a CGI environment.
  73
  74   Compared to wsgiref.handlers.CGIHandler().run(application), this
  75   function takes some shortcuts.  Those are possible because the
  76   app server makes stronger promises than the CGI standard.
  77
  78   Also, this function may wrap custom WSGI middleware around the
  79   application.  (You can use run_bare_wsgi_app() to run an application
  80   without adding WSGI middleware, and add_wsgi_middleware() to wrap
  81   the configured WSGI middleware around an application without running
  82   it.  This function is merely a convenient combination of the latter
  83   two.)
  84
  85   To configure custom WSGI middleware, define a function
  86   webapp_add_wsgi_middleware(app) to your appengine_config.py file in
  87   your application root directory:
  88
  89     def webapp_add_wsgi_middleware(app):
  90       app = MiddleWareClassOne(app)
  91       app = MiddleWareClassTwo(app)
  92       return app
  93
  94   You must import the middleware classes elsewhere in the file.  If
  95   the function is not found, no WSGI middleware is added.
  96   """
  97   run_bare_wsgi_app(add_wsgi_middleware(application))
  98
  99
 100 def add_wsgi_middleware(application):
 101   """Wrap WSGI middleware around a WSGI application object."""
 102   return _config_handle.add_wsgi_middleware(application)
 103
 104
 105 def run_bare_wsgi_app(application):
 106   """Like run_wsgi_app() but doesn't add WSGI middleware."""
 107   env = dict(os.environ)
 108   env["wsgi.input"] = sys.stdin
 109   env["wsgi.errors"] = sys.stderr
 110   env["wsgi.version"] = (1, 0)
 111   env["wsgi.run_once"] = True
 112   env["wsgi.url_scheme"] = wsgiref.util.guess_scheme(env)
 113   env["wsgi.multithread"] = False
 114   env["wsgi.multiprocess"] = False
 115   result = application(env, _start_response)
 116   if result is not None:
 117     for data in result:
 118       sys.stdout.write(data)
 119
 120
 121 def _start_response(status, headers, exc_info=None):
 122   """A start_response() callable as specified by PEP 333"""
 123   if exc_info is not None:
 124     raise exc_info[0], exc_info[1], exc_info[2]
 125   print "Status: %s" % status
 126   for name, val in headers:
 127     print "%s: %s" % (name, val)
 128   print
 129   return sys.stdout.write