Django中间件工作流程及写法实例代码

MIDDLEWARE_CLASSES = (
  'django.contrib.sessions.middleware.SessionMiddleware','django.middleware.common.CommonMiddleware',...    
)

import time
from importlib import import_module

from django.conf import settings
from django.utils.cache import patch_vary_headers
from django.utils.http import cookie_date


class SessionMiddleware(object):
  def __init__(self):
    engine = import_module(settings.SESSION_ENGINE)
    self.SessionStore = engine.SessionStore

  def process_request(self,request):
    session_key = request.COOKIES.get(settings.SESSION_COOKIE_NAME,None)
    request.session = self.SessionStore(session_key)

  def process_response(self,request,response):
    """
    If request.session was modified,or if the configuration is to save the
    session every time,save the changes and set a session cookie or delete
    the session cookie if the session has been emptied.
    """
    try:
      accessed = request.session.accessed
      modified = request.session.modified
      empty = request.session.is_empty()
    except AttributeError:
      pass
    else:
      # First check if we need to delete this cookie.
      # The session should be deleted only if the session is entirely empty
      if settings.SESSION_COOKIE_NAME in request.COOKIES and empty:
        response.delete_cookie(settings.SESSION_COOKIE_NAME)
      else:
        if accessed:
          patch_vary_headers(response,('Cookie',))
        if modified or settings.SESSION_SAVE_EVERY_REQUEST:
          if request.session.get_expire_at_browser_close():
            max_age = None
            expires = None
          else:
            max_age = request.session.get_expiry_age()
            expires_time = time.time() + max_age
            expires = cookie_date(expires_time)
          # Save the session data and refresh the client cookie.
          # Skip session save for 500 responses,refs #3881.
          if response.status_code != 500:
            request.session.save()
            response.set_cookie(settings.SESSION_COOKIE_NAME,request.session.session_key,max_age=max_age,expires=expires,domain=settings.SESSION_COOKIE_DOMAIN,path=settings.SESSION_COOKIE_PATH,secure=settings.SESSION_COOKIE_SECURE or None,httponly=settings.SESSION_COOKIE_HTTPONLY or None)
    return response

# -*- coding:utf-8 -*-
from datetime import datetime
from data_monitor.utils.dbmanager import MysqlManager
from data_monitor.common.constant import MYSQL_JOBS as mysql_config

class RequestHookMiddleware(object):

  def process_request(self,request):
    try:
      username = request.COOKIES.get('username')
      uri = request.path
      timestamp = str(datetime.now())
      db_obj = MysqlManager(
        mysql_config.get('host'),mysql_config.get('port'),mysql_config.get('db'),mysql_config.get('user'),mysql_config.get('password'),format=True,)
      field_str = 'username,uri,timestamp'
      value_str = '"%s","%s","%s"' % (username,timestamp)
      db_obj.insert('pv',field_str,value_str)
      db_obj.close()
      return
    except Exception,ex:
      return