| .. _tutorials.gettingstarted.handlingforms: |
| |
| Handling Forms with webapp2 |
| =========================== |
| If we want users to be able to post their own greetings, we need a way to |
| process information submitted by the user with a web form. The ``webapp2`` |
| framework makes processing form data easy. |
| |
| |
| Handling Web Forms With webapp2 |
| ------------------------------- |
| Replace the contents of ``helloworld/helloworld.py`` with the following:: |
| |
| import cgi |
| |
| from google.appengine.api import users |
| import webapp2 |
| |
| class MainPage(webapp2.RequestHandler): |
| def get(self): |
| self.response.out.write(""" |
| <html> |
| <body> |
| <form action="/sign" method="post"> |
| <div><textarea name="content" rows="3" cols="60"></textarea></div> |
| <div><input type="submit" value="Sign Guestbook"></div> |
| </form> |
| </body> |
| </html>""") |
| |
| class Guestbook(webapp2.RequestHandler): |
| def post(self): |
| self.response.out.write('<html><body>You wrote:<pre>') |
| self.response.out.write(cgi.escape(self.request.get('content'))) |
| self.response.out.write('</pre></body></html>') |
| |
| application = webapp2.WSGIApplication([ |
| ('/', MainPage), |
| ('/sign', Guestbook) |
| ], debug=True) |
| |
| def main(): |
| application.run() |
| |
| if __name__ == "__main__": |
| main() |
| |
| Reload the page to see the form, then try submitting a message. |
| |
| This version has two handlers: ``MainPage``, mapped to the URL ``/``, displays |
| a web form. ``Guestbook``, mapped to the URL ``/sign``, displays the data |
| submitted by the web form. |
| |
| The ``Guestbook`` handler has a ``post()`` method instead of a ``get()`` |
| method. This is because the form displayed by ``MainPage`` uses the HTTP POST |
| method (``method="post"``) to submit the form data. If for some reason you |
| need a single handler to handle both GET and POST actions to the same URL, you |
| can define a method for each action in the same class. |
| |
| The code for the ``post()`` method gets the form data from ``self.request``. |
| Before displaying it back to the user, it uses ``cgi.escape()`` to escape |
| HTML special characters to their character entity equivalents. ``cgi`` is a |
| module in the standard Python library; see `the documentation for cgi <http://www.python.org/doc/2.5.2/lib/module-cgi.html>`_ |
| for more information. |
| |
| .. note:: |
| The App Engine environment includes the entire Python 2.5 standard library. |
| However, not all actions are allowed. App Engine applications run in a |
| restricted environment that allows App Engine to scale them safely. |
| For example, low-level calls to the operating system, networking operations, |
| and some filesystem operations are not allowed, and will raise an error |
| when attempted. For more information, see `The Python Runtime Environment <http://code.google.com/appengine/docs/python/>`_. |
| |
| |
| Next... |
| ------- |
| Now that we can collect information from the user, we need a place to put it |
| and a way to get it back. |
| |
| Continue to :ref:`tutorials.gettingstarted.usingdatastore`. |
