We will use the BaseHTTPServer as the web server.
The controller base class
All the controller needs is a reference to the BaseHTTPServer so that it can access the web request and write out the response.
class Controller(object):
def __init__(self, server):
self.__server = server
@property
def server(self):
return self.__server
The router
The router needs to manipulate the request and response but also instanciate the controllers, that is why it receives an instance of BaseHTTPServer.
The routes are defined by 3 components:
- A regular expression that must be matched to trigger the route
- A controller class to be instanciated
- A method name to be called on the controller
The tricky part here is to instanciate the controller and call a method on it.
class Router(object):
def __init__(self, server):
self.__routes = []
self.__server = server
def addRoute(self, regexp, controller, action):
self.__routes.append({'regexp': regexp, 'controller': controller, 'action': action})
def route(self, path):
for route in self.__routes:
if re.search(route['regexp'], path):
cls = globals()[route['controller']]
func = cls.__dict__[route['action']]
obj = cls(self.__server)
apply(func,(obj, ))
return
# Not found
self.__server.send_response(404)
self.__server.end_headers()
The request handler
All the request handler needs to do is to instanciate the Router and add to it the routes it needs to manage.
This simple request handler is only able to reply to GET requests.
class MyRequestHandler(BaseHTTPRequestHandler):
def __init__(self, request, client_address, server):
routes = [
{'regexp': r'^/$', 'controller': 'HomeController', 'action': 'indexAction'},
{'regexp': r'^/content/', 'controller': 'ContentController', 'action': 'showAction'}
]
self.__router = Router(self)
for route in routes:
self.__router.addRoute(route['regexp'], route['controller'], route['action'])
BaseHTTPRequestHandler.__init__(self, request, client_address, server)
def do_GET(self):
self.__router.route(self.path)
A simple Hello World controller
class HomeController(Controller):
def __init__(self, server):
Controller.__init__(self, server)
def indexAction(self):
self.server.send_response(200)
self.server.send_header('Content-type', 'text/html')
self.server.end_headers()
self.server.wfile.write('Hello world')
By the way, in MVC a controller should not do View stuff, see "Going further with a templating engine" below to make the separation better using a view layer.
A controller rendering a file
This controller will serve a file in the "public/" directory. Be carefull there is not enough error checking in this code...
class ContentController(Controller):
CONTENT_BASE_PATH = 'public/'
def __init__(self, server):
Controller.__init__(self, server)
def showAction(self):
filename = ContentController.CONTENT_BASE_PATH + self.server.path[9:]
if os.access(filename, os.R_OK) and not os.path.isdir(filename):
#TODO: is there any possibility to access files outside the root with ..?
file = open(filename, "r")
content = file.read()
file.close()
#TODO: set correct content type
self.server.send_response(200)
self.server.send_header('Content-type', 'text/html')
self.server.end_headers()
self.server.wfile.write(content)
else:
self.server.send_response(404)
self.server.end_headers()
Running the server
What we have defined here is a simple http server that will reply "Hello world" when the URL "/" is accessed, and return the content of a file named myFile (if it exists) when the URL "/content/myFile" is reached.
def main():
try:
httpd = HTTPServer(('', 8000), MyRequestHandler)
print 'Server started...'
httpd.serve_forever()
except:
print 'Server shutting down'
httpd.socket.close()
if __name__ == '__main__':
main()
Going further with a templating engine
It is quite simple to integrate a templating engine like Cheetah in this code.
Here is a example of controller rendering a template:
class TemplateController(Controller):
def __init__(self, server):
Controller.__init__(self, server)
def listAction(self):
self.server.send_response(200)
self.server.send_header('Content-type', 'text/html')
self.server.end_headers()
self.server.wfile.write(Template ( file = 'templates/hello_world.tmpl', searchList = [{ }] ))
return
Conclusion
That's the reason why I love Python so much, in very few lines we could implement basic MVC over a simple web server.
