import traceback
import sys
import urllib
from os.path import abspath, join, dirname
from functools import partial, lru_cache
from inspect import ismodule, isclass
from zest.core import is_async, Config, AsyncFile, get_param_length
from zest.httputil import (Request, Response, HTTPError,
JsonResponse, RedirectResponse)
from zest.helper import default_config
from zest.helper.util import get_logger, utc_time
from zest.helper.consts import ERROR_TEMPLETE, HTTP_STATUS
from zest.routing import Router
logger = get_logger('zest.web')
G_TEMPLATE_ENGINE = None # global template engine.
G_TEMPLATE = {} # global template variable or funtion
G_ROUTER = None # global router
class App:
""" The main entry of a Web app.
Each App instance represents an WSGI application, which contains
router, template, config, resources and so on.
Parameters:
