class CommonDispatcher implements Dispatcher {
    private $router,$error404;
    protected $context;
    protected $factory;

    function __construct(Router $router, HttpContext $context,
        Factory $controllerFactory, $error404Controller='Error404')
    {
        $this->router = $router;
        $this->context = $context;
        $this->factory = $controllerFactory;
        $this->error404 = $error404Controller;
    }

    function dispatch() {
        $url = $this->getUrl();
        $method = 'defaultAction';
        $ctrl = null;
        try {
            if ( $url == '/' ) {
                $ctrl = $this->factory->produce('Index');
            } else {
                $route = $this->router->findRoute($url);
                $ctrl = $this->factory->produce($route->getMapClass());
                if ( $route->getMapMethod() ) {
                    if ( method_exists($ctrl, $route->getMapMethod()) ) {
                        $method = $route->getMapMethod();
                    } else {
                        $ctrl = $this->factory->produce($this->error404);
                    }
                }
            }
        } catch ( ClassLoaderException $e ) {
            $ctrl = $this->factory->produce($this->error404);
        }
        $this->executeAction($ctrl, $method);
    }

    protected function executeAction(Action $ctrl, $method) {
        $ctrl->$method();
    }

    protected function getUrl() {
        $url = $this->context->getServer()->getStr('REQUEST_URI', '/');
        $parts = explode('?', $url);
        return (sizeof($parts) > 1? $parts[0] : $url);
    }

}