中间件和Django缓存

中间件定义：

　　中间件是一个、一个的管道，如果相对任何所有的通过Django的请求进行管理都需要自定义中间件

　　中间件可以对进来的请求和出去的请求进行控制

　　中间件是一类。

看下面的代码在settings里中间件的类：

 

MIDDLEWARE_CLASSES = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    # 'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

 

当有请求过来的时候，默认从上倒下执行！然后在返回的时候从下面在返回回去，如下图：

2、自定义中间件

中间件中可以定义四个方法，分别是：

• process_request(self,request)
• process_view(self, request, callback, callback_args, callback_kwargs)
• process_exception(self, request, exception)
• process_response(self, request, response)

process_exception 这个方法只有在出现错误的时候才会触发

先写一个自定义中间件，然后在看他的原理和源码：

2.1、自定义中间件

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" alt="" />\

 

class Testmiddle(object):
    def process_request(self,request):
        print 'Testmiddle process_request'
    def process_view(self, request, callback, callback_args, callback_kwargs):
        print 'Testmiddle process_view'
    def process_exception(self, request, exception):
        pass
    def process_response(self, request, response):
        print 'Testmiddle process_response'
        return response

class Nextmiddle(object):
    def process_request(self,request):
        print 'Nextmiddle process_request'
    def process_view(self, request, callback, callback_args, callback_kwargs):
        print 'Nextmiddle process_view'
    def process_exception(self, request, exception):
        pass
    def process_response(self, request, response):
        print 'Nextmiddle process_response'
        return response

 

2.2、注册中间件

 

MIDDLEWARE_CLASSES = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
   # 'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'middleware.middle.Testmiddle',
    'middleware.middle.Nextmiddle',
]

 

2.3、测试使用url和views

from app01 import views
urlpatterns = [
    url(r'^admin/', admin.site.urls),
    url(r'^index/$', views.index),

]

def index(request):
    print 'This app01 Views.index'
    return HttpResponse('OK')

2.4、查看输出结果：

 

'''
Testmiddle process_request
Nextmiddle process_request
Testmiddle process_view
Nextmiddle process_view
This app01 Views.index
Nextmiddle process_response
Testmiddle process_response
'''

 

从输出结果可以看出：

他是先执行Testmiddle 的request 方法又执行了Nextmiddle的 process_request方法。。。。

2.5、原理：

当请求进来了到达中间件

去settings里面找到MIDDLEWARE_CLASSES，MIDDLEWARE_CLASSES是一个元组

有4个列表：

 

process_request_lsit = []
process_view_list = []
process_response_list = []
然后他循环MIDDLEWARE_CLASSES这个类：
for 类 in MIDDLEWARE_CLASSES：
　　obj = 类()
　　if obj里有process_request方法：
　　　　process_request_lsit.append(obj.process_request)

 

然后循环后后执行：

for i in process_request_list:
　　i() #加括号执行方法

for i in process_view_list:
    i()
    ............

3、中间件的流程梳理

首先看下自定义的中间件中的process_response方法他是有返回值的其他的是没有返回值的。这个return response是什么呢？

这个response就是咱们自定义的views.index返回的结果！

    def process_response(self, request, response):
        print 'Testmiddle process_response'
        return response

如果在其他的没有返回值得，仅有process_response有返回值得话他的请求流程是这样的：

但是如果在process_request或者process_view又返回值得话那么流程就完全不一样了！

举例：如果有m1和m2两个中间件,如果我在m1中的request方法中设置了，如果访问为1.1.1.1那么返回要一个404，那么他的访问流程是这样的：

process_exception  什么时候触发呢？咱们定义的views.index出错的时候他就会捕捉到然后执行咱们定义的process_exception方法如下图：

Django缓存

由于Django是动态网站，所有每次请求均会去数据进行相应的操作，当程序访问量大时，耗时必然会更加明显，最简单解决方式是使用：缓存，缓存将一个某个views的返回值保存至内存或者Redis中，5分钟内再有人来访问时，则不再去执行view中的操作，而是直接从内存或者Redis中之前缓存的内容拿到，并返回。

举个例子来说：如果访问量比较大的时候，有很多相同的操作比如：有时候请求的数据比如访问同一条数据，或者同一个页面的时候，其实是没必要的。

Django支持，mysql，Redis、Memecache、文件的方式做缓存，并且可以设置超时时间。

settings配置：

CACHES = {
    'default': {
        #定义已文件的方式进行cache
        'BACKEND': 'django.core.cache.backends.filebased.FileBasedCache',
        #cache文件的存放路径
        'LOCATION': os.path.join(BASE_DIR, 'cache'),
        #超时时间为600妙
        'TIMEOUT': 600,
        'OPTIONS': {
            'MAX_ENTRIES': 1000
        }
    }
}

给请求应用，就是使用装饰器

from django.views.decorators.cache import cache_page

#这里设置的是 60秒 * 15 ,15分钟之后
@cache_page(60 * 15)
def cache_page(request):
    current = str(time.time())
    return HttpResponse(current)