Hello WebApp 분석

webapp 어플리케이션은 세가지 파트로 구성되어있다:

• 요구를 처리하고 반응하는 하나 혹은 그 이상의 RequestHandler 클래스
• URL 기반의 핸들러로 들어온 요구를 라우트하는 WSGIApplication 인스턴스
• CGI adaptor를 사용하여 WSGIApplication을 실행하는 메인 루틴

webapp 어플리케이션에 어울리게 기존의 helloworld.py 를 수정하여 다음과 같이 다시 코딩해보자:

from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app

class MainPage(webapp.RequestHandler):
  def get(self):
      self.response.headers['Content-Type'] = 'text/plain'
      self.response.out.write('Hello, webapp World!')

application = webapp.WSGIApplication(
                                   [('/', MainPage)],
                                   debug=True)

def main():
  run_wsgi_app(application)

if __name__ == "__main__":
  main()

run_wsgi_app(application)

Runs a WSGI application in App Engine's CGI environment. This is comparable to using a WSGI-to-CGI adaptor such as the one provided by the wsgirefmodule of the Python standard library, but has several advantages: run_wsgi_app() automatically detects whether the application is running in the development server, and if so outputs errors to the browser in addition to the log. run_wsgi_app() also allows App Engine to send data output by the handler prior to the error, which wsgiref.handlers.CGIHandler doesn't do.

Arguments:

application

A WSGI application object, such as webapp.WSGIApplication.

The WSGIApplication Class

The google.appengine.ext.webapp package provides the following classes:

class WSGIApplication(url_mapping, debug=False)

A WSGI-compatible application that maps URL paths to RequestHandler classes. An App Engine CGI script creates a WSGIApplication object, then runs it using a WSGI CGI handler such as run_wsgi_app().

Arguments:

url_mapping

A mapping of URL paths to request handlers, as a list of tuples where each tuple is a path-to-handler mapping. The first element of the tuple specifies the URL path as a string. The second element of the tuple is the constructor of a request handler class, a subclass of RequestHandler.

debug

If True, the application runs in "debug mode." Primarily, this means that the request handler's handle_exception() method is called with debug_mode=Truewhen the handler raises an exception, which prints debugging information to the web browser.

출처

• http://code.google.com/appengine/docs/python/gettingstarted/usingwebapp.html
• http://code.google.com/appengine/docs/python/tools/webapp/utilmodule.html#run_wsgi_app
• http://code.google.com/appengine/docs/python/tools/webapp/wsgiapplicationclass.html