Posting from one RequestHandler to another in App Engine

Goal: Using app engine's basic webapp framework I want to create a new request, with post data, to send to another RequestHandler. Something like pageGenerator.post({'message':'the message','datum1':datum1,...})...

Problem Description: One request handler, call it pageGenerator, creates a page with a form on it. When the user submits the form, the post goes to a different handler: dat开发者_Python百科aProcessor. If dataProcessor finds some problem with the submitted data it would send the submitted data plus an Error Message to 'pageGenerator`'s post method, and pageGenerator would serve up the page with the error message.

How do I pass data (and control) back and forth like this? I would like pageGenerator to be able to get the data with self.request.get('message').

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Sounds like you're over-complicating things. Consider just having a common method to show the form that can be invoked in different circumstances:

class FormHandler(webapp.RequestHandler):

  def get(self):
    self.show_form()

  def post(self):
    if form_is_valid():
      handle_success()
    else:
      self.show_form({'feedback':'Validation failed'})

  def show_form(self, vals={}):
    vals['field1'] = self.request.get('field1')
    vals['field2'] = self.request.get('field2')
    html = template.render('form.html', vals)
    self.response.out.write(html)

If you really need "display form" and "process form" to be in different handler classes, you can accomplish the same thing by defining show_form() in a common parent class.