中间件 middleware

中间件的五个方法

中间件可以定义五个方法,分别是:(主要的是process_request和process_response)

process_request(self,request)
process_view(self, request, view_func, view_args, view_kwargs)
process_template_response(self,request,response)
process_exception(self, request, exception)
process_response(self, request, response)

定义

 中间件顾名思义,是介于request与response处理之间的一道处理过程,相对比较轻量级,并且在全局上改变django的输入与输出。因为改变的是全局,所以需要谨慎实用,用不好会影响到性能。

settings配置中

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]
配置的是一个个路径,封装一些功能,相当于
from django.middleware.security import SecurityMiddleware

登录验证

条件:只有登录成功才能访问各个页面,也就是无论点击哪里都跳转到登录界面

用session时会报一个错误

low版本 装饰器版

views.py

from django.shortcuts import render,HttpResponse,redirect

# Create your views here.

def wrapper(f):
    def inner(request,*args,**kwargs):
        status = request.session.get("is_login")
        # 获取session的值,
        if status:
            return f(request,*args,**kwargs)
        else:
            return redirect("login")
    return inner

@wrapper
def home(request):

    return render(request,"home.html")

def login(request):
    if request.method == "GET":
        return render(request,"login.html")
    else:
        user = request.POST.get("username")
        pwd = request.POST.get("password")
        if user == "alex" and pwd == "123":
            request.session["is_login"] = True
            return redirect("home")
        else:
            return redirect("login")

@wrapper
def index(request):
    return render(request,"index.html")

高级版

1.设置自定义中间件

在应用app01中

在应用app01中创建一个包,随便起名字,一般都放在一个叫做utils的包里面,表示一个公用的组件,创建一个py文件,随便起名字,例如叫做:middlewares.py,内容如下

from django.utils.deprecation import MiddlewareMixin

class LoginAuth(MiddlewareMixin):
    #请求来了,自动执行
    def process_request(self,request):
        print("请求来了")

然后去settings中的MIDDLEWARE中设置中间件地址

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'app01.utils.mymiddleware.LoginAuth'
]

django的请求生命周期

具体解释

  1. 浏览器请求,wsgi.py,它封装这socket,request对象,request对象给中间键,中间件根据middleware封装的中间件一层一层向下执行,自动执行每个中间件中的请求函数

  2. 执行顺序从上到下,例如,我们把自定义的中间件放在session中间件的上边,那么session就不起作用了,所以自定义的中间件是放在最下边位置

  3. 中间件加工完之后,给了url控制器,然后执行视图函数views,视图函数再通过orm与数据库进行交互,并且渲染页面

    注意如果此处没有return值,默认返回的是None,表示正常,向下执行,如果return值是别的值,那么就不会向下执行了,直接执行响应中间件的response方法给浏览器了

  4. 执行完成后,页面需要间数据返还给浏览器,不需要经过url,但是还会经过中间件

  5. 中间件中执行process_response方法

所以由上引入白名单概念,就是让不需要session的函数先执行,例如login函数

白名单

中间件的py文件中

from django.utils.deprecation import MiddlewareMixin
from django.shortcuts import render,HttpResponse,redirect
class LoginAuth(MiddlewareMixin):
    #白名单
    white_list = ["/login/",]
    def process_request(self,request):
        print("请求来了")
        path = request.path
        #获取请求路径
        if path not in self.white_list:
            status = request.session.get("is_login")
            if not status:
                return redirect("login")


    def process_response(self,request,response):
        print("响应走了")
        return response

views.py 应用了中间件就不用了装饰器了

from django.shortcuts import render,HttpResponse,redirect

# Create your views here.

def home(request):
    print("这是home函数")
    return render(request,"home.html")

def login(request):
    if request.method == "GET":
        print("这是login函数")
        return render(request,"login.html")
    else:
        user = request.POST.get("username")
        pwd = request.POST.get("password")
        if user == "alex" and pwd == "123":
            request.session["is_login"] = True
            return redirect("home")
        else:
            return redirect("login")

def index(request):
    print("这是index函数")
    return render(request,"index.html")

在上述代码中,请求白名单中的数据时,根据请求路径判断下列条件的结果,当路径在白名单中的时候,if条件不成立,默认返回None,正常执行views函数,如果访问home函数等,以为没有在白名单中,执行if条件,如果已经有了session值,则默认返回None,正常执行函数,如果没有session,则执行下一个if判断,重定向到login路径,再次请求,执行同上

中间件有多个方法时的执行顺序

settings中

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    # 'app01.utils.mymiddleware.LoginAuth'
    'app01.utils.mymiddleware.MD1',  # 新增中间件
    "app01.utils.mymiddleware.MD2",  # 新增中加件
]

views.py

from django.shortcuts import render,HttpResponse,redirect

# Create your views here.

def home(request):
    print("这是home函数")
    return render(request,"home.html")

def login(request):
    if request.method == "GET":
        print("这是login函数")
        return render(request,"login.html")
    else:
        user = request.POST.get("username")
        pwd = request.POST.get("password")
        if user == "alex" and pwd == "123":
            request.session["is_login"] = True
            return redirect("home")
        else:
            return redirect("login")

def index(request):
    print("这是index函数")
    return render(request,"index.html")

process_resquest 和 process_response 方法顺序

middleware.py 中间件中文件

class MD1(MiddlewareMixin):
    def process_request(self,request):
        #request是一个请求的对象
        print("MD1的process_request方法",request)
        #return HttpResponse("ok")   ---------------------- 第一知识点  第一执行

    def process_response(self,request,response):
        print("MD1的process_response方法",response)
        return response
        #return HttpResponse("ok")  ---------------------- 第二知识点  第四执行

class MD2(MiddlewareMixin):
    def process_request(self,request):
        print("MD2的process_request方法",request)
        #return HttpResponse("ok")  ----------------------- 第三知识点   第二执行

    def process_response(self,request,response):
        print("MD2的process_response方法",response)
        #response 接收的是函数的返回值,是一个response对象
        return response
        #return HttpResponse("ok")  ---------------------- 第四知识点    第三执行

有return自定义内容的时候

都是get方法时验证

第一知识点解释

MD1的process_request方法 <WSGIRequest: GET '/index/'>
MD1的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">
当我们在浏览器发送请求时,执行到中间件时就不再向后执行,只执行返回函数process_response

第二知识点解释

MD1的process_request方法 <WSGIRequest: GET '/index/'>
MD2的process_request方法 <WSGIRequest: GET '/index/'>
这是index函数
MD2的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">
MD1的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">
当我们在浏览器发送请求时,由于返回值的位置是最后执行的,所以所有的函数都执行了,但是由于返回的是自定义的,而不是response对象,所以返回页面不是html文件,而是ok

第三知识点解释

MD1的process_request方法 <WSGIRequest: GET '/login/'>
MD2的process_request方法 <WSGIRequest: GET '/login/'>
MD2的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">
MD1的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">
当我们在浏览器发送请求时,执行到中间件时就不再向后执行,只执行返回函数process_response,依次向上执行(中间件顺序) 所以返回页面不是html文件,而是ok

第四知识点解释

MD1的process_request方法 <WSGIRequest: GET '/login/'>
MD2的process_request方法 <WSGIRequest: GET '/login/'>
这是login函数
MD2的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">
MD1的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">
当我们在浏览器发送请求时,由于返回值的位置是最后执行的,所以所有的函数都执行了,但是由于返回的是自定义的,而不是response对象,所以返回页面不是html文件,而是ok

process_view

middleware.py

class MD1(MiddlewareMixin):
    def process_request(self,request):
        #request是一个请求的对象
        print("MD1的process_request方法",request)
        # return HttpResponse("ok")

    def process_response(self,request,response):
        print("MD1的process_response方法",response)
        return response
        # return HttpResponse("ok")

    def process_view(self,request,view_func,view_args,view_kwargs):
        print(view_func)
        print("MD1的process_view")

class MD2(MiddlewareMixin):
    def process_request(self,request):
        print("MD2的process_request方法",request)
        # return HttpResponse("ok")

    def process_response(self,request,response):
        print("MD2的process_response方法",response)
        #response 接收的是函数的返回值,是一个response对象
        return response
        # return HttpResponse("ok")

    def process_view(self,request,view_func,view_args,view_kwargs):
        print(view_func)
        print("MD2的process_view")

index请求结果

MD1的process_request方法 <WSGIRequest: GET '/login/'>
MD2的process_request方法 <WSGIRequest: GET '/login/'>
<function login at 0x0000002B48EDA2F0>
MD1的process_view
<function login at 0x0000002B48EDA2F0>
MD2的process_view
这是login函数
MD2的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">
MD1的process_response方法 <HttpResponse status_code=200, "text/html; charset=utf-8">

执行顺序图

process_exception

这个比较特殊,只有在有报错的情况下才执行,否则不执行

middleware.py

class MD1(MiddlewareMixin):
    def process_request(self,request):
        #request是一个请求的对象
        print("MD1的process_request方法",request)
        # return HttpResponse("ok")

    def process_response(self,request,response):
        print("MD1的process_response方法",response)
        return response
        # return HttpResponse("ok")

    def process_view(self,request,view_func,view_args,view_kwargs):
        print(view_func)
        print("MD1的process_view")

    def process_exception(self, request, exception):
        print(exception)
        print("MD1的process_exception")

class MD2(MiddlewareMixin):
    def process_request(self,request):
        print("MD2的process_request方法",request)
        # return HttpResponse("ok")

    def process_response(self,request,response):
        print("MD2的process_response方法",response)
        #response 接收的是函数的返回值,是一个response对象
        return response
        # return HttpResponse("ok")

    def process_view(self,request,view_func,view_args,view_kwargs):
        print(view_func)
        print("MD2的process_view")

    def process_exception(self, request, exception):
        print(exception)    #打印的是抛出的错误信息
        print("MD2的process_exception")

为了报错修改views.py代码

def home(request):
    print("这是home函数")
    return render(request,"home.html")

def login(request):
    if request.method == "GET":
        print("这是login函数")
        raise ValueError("抛出错误")   #------注意此处要抛错才能执行exception
        return render(request,"login.html")
    else:
        user = request.POST.get("username")
        pwd = request.POST.get("password")
        if user == "alex" and pwd == "123":
            request.session["is_login"] = True
            return redirect("home")
        else:
            return redirect("login")

def index(request):
    print("这是index函数")
    return render(request,"index.html")

执行结果

MD1的process_request方法 <WSGIRequest: GET '/login/'>
MD2的process_request方法 <WSGIRequest: GET '/login/'>
<function login at 0x0000000AD8F5A268>
MD1的process_view
<function login at 0x0000000AD8F5A268>
MD2的process_view
这是login函数
抛出错误
MD2的process_exception
抛出错误
MD1的process_exception
Internal Server Error: /login/
Traceback (most recent call last):
  File "C:\Python36\lib\site-packages\django\core\handlers\exception.py", line 41, in inner
    response = get_response(request)
  File "C:\Python36\lib\site-packages\django\core\handlers\base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "C:\Python36\lib\site-packages\django\core\handlers\base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "D:\Django项目\day67\zhongjianjian\app01\views.py", line 23, in login
    raise ValueError("抛出错误")
ValueError: 抛出错误
[16/Oct/2019 17:25:55] "GET /login/ HTTP/1.1" 500 65127
MD2的process_response方法 <HttpResponse status_code=500, "text/html">
MD1的process_response方法 <HttpResponse status_code=500, "text/html">
02-10 08:28