Django-分页和中间件
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分页
Django的分页器(paginator)
view
from django.shortcuts import render,HttpResponse # Create your views here. from app01.models import * from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger def index(request): \'\'\' 批量导入数据: Booklist=[] for i in range(100): Booklist.append(Book(title="book"+str(i),price=30+i*i)) Book.objects.bulk_create(Booklist) \'\'\' \'\'\' 分页器的使用: book_list=Book.objects.all() paginator = Paginator(book_list, 10) print("count:",paginator.count) #数据总数 print("num_pages",paginator.num_pages) #总页数 print("page_range",paginator.page_range) #页码的列表 page1=paginator.page(1) #第1页的page对象 for i in page1: #遍历第1页的所有数据对象 print(i) print(page1.object_list) #第1页的所有数据 page2=paginator.page(2) print(page2.has_next()) #是否有下一页 print(page2.next_page_number()) #下一页的页码 print(page2.has_previous()) #是否有上一页 print(page2.previous_page_number()) #上一页的页码 # 抛错 #page=paginator.page(12) # error:EmptyPage #page=paginator.page("z") # error:PageNotAnInteger \'\'\' book_list=Book.objects.all() paginator = Paginator(book_list, 10) page = request.GET.get(\'page\',1) currentPage=int(page) try: print(page) book_list = paginator.page(page) except PageNotAnInteger: book_list = paginator.page(1) except EmptyPage: book_list = paginator.page(paginator.num_pages) return render(request,"index.html",{"book_list":book_list,"paginator":paginator,"currentPage":currentPage})
index.html:
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Title</title> <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous"> </head> <body> <div class="container"> <h4>分页器</h4> <ul> {% for book in book_list %} <li>{{ book.title }} -----{{ book.price }}</li> {% endfor %} </ul> <ul class="pagination" id="pager"> {% if book_list.has_previous %} <li class="previous"><a href="/index/?page={{ book_list.previous_page_number }}">上一页</a></li> {% else %} <li class="previous disabled"><a href="#">上一页</a></li> {% endif %} {% for num in paginator.page_range %} {% if num == currentPage %} <li class="item active"><a href="/index/?page={{ num }}">{{ num }}</a></li> {% else %} <li class="item"><a href="/index/?page={{ num }}">{{ num }}</a></li> {% endif %} {% endfor %} {% if book_list.has_next %} <li class="next"><a href="/index/?page={{ book_list.next_page_number }}">下一页</a></li> {% else %} <li class="next disabled"><a href="#">下一页</a></li> {% endif %} </ul> </div> </body> </html>
扩展
def index(request): book_list=Book.objects.all() paginator = Paginator(book_list, 15) page = request.GET.get(\'page\',1) currentPage=int(page) # 如果页数十分多时,换另外一种显示方式 if paginator.num_pages>30: if currentPage-5<1: pageRange=range(1,11) elif currentPage+5>paginator.num_pages: pageRange=range(currentPage-5,paginator.num_pages+1) else: pageRange=range(currentPage-5,currentPage+5) else: pageRange=paginator.page_range try: print(page) book_list = paginator.page(page) except PageNotAnInteger: book_list = paginator.page(1) except EmptyPage: book_list = paginator.page(paginator.num_pages) return render(request,"index.html",locals())
例子
views
def StudentList(request): # l=[] # for i in range(50): # l.append(models.Student(sname="stu"+str(i),age=21,sex="male",email="stu@qq.com",phone="1478955",addr="北京",classes_id=2,headmaster_id=1)) # models.Student.objects.bulk_create(l) studentlist=models.Student.objects.all() paginator=Paginator(studentlist,6) pageNums=paginator.num_pages num=request.GET.get("page",1) currentPage=int(num) if pageNums>9: if currentPage-5<1: page_range=range(1,10) elif currentPage+5>pageNums: page_range=range(currentPage-5,pageNums+1) else: page_range=range(currentPage-5,currentPage+5) else: page_range = paginator.page_range studentlist=paginator.page(num) return render(request,"StudentList.html",{"studentlist":studentlist,"page_range":page_range,"pageNums":pageNums,"currentPage":currentPage})
html
<nav aria-label="Page navigation" id="paging"> <ul class="pagination"> <li><a href="/appStudent/StudentList/?page=1">首页</a></li> {% if studentlist.has_previous %} <li> <a href="/appStudent/StudentList/?page={{ studentlist.previous_page_number }}" aria-label="Previous"> <span aria-hidden="true">«</span> </a> </li> {% else %} <li class="disabled"> <a href="#" aria-label="Previous"> <span aria-hidden="true">«</span> </a> </li> {% endif %} {% for page in page_range %} {% if currentPage == page %} <li class="active"><a href="/appStudent/StudentList/?page={{ page }}">{{ page }}</a></li> {% else %} <li><a href="/appStudent/StudentList/?page={{ page }}">{{ page }}</a></li> {% endif %} {% endfor %} {% if BookList.has_next %} <li> <a href="/appStudent/StudentList/?page={{ studentlist.next_page_number }}" aria-label="Next"> <span aria-hidden="true">»</span> </a> </li> {% else %} <li class="disabled"> <a href="#" aria-label="Next"> <span aria-hidden="true">»</span> </a> </li> {% endif %} <li><a href="/appStudent/StudentList/?page={{ pageNums }}">尾页</a></li> <li> <span>共{{ pageNums }}页</span></li> </ul> </nav>
中间件
中间件的概念
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。
Django的中间件的定义:
Middleware is a framework of hooks into Django’s request/response processing. <br>It’s a light, low-level “plugin” system for globally altering Django’s input or output.
如果你想修改请求,例如被传送到view中的HttpRequest对象。 或者你想修改view返回的HttpResponse对象,这些都可以通过中间件来实现。
可能你还想在view执行之前做一些操作,这种情况就可以用 middleware来实现。
大家可能频繁在view使用request.user
吧。 Django想在每个view执行之前把user设置为request的属性,于是就用了一个中间件来实现这个目标。所以Django提供了可以修改request 对象的中间件 AuthenticationMiddleware
。
Django默认的Middleware
:
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\', ]
每一个中间件都有具体的功能
自定义中间件
中间件中一共有四个方法:
process_request
process_view
process_exception
process_response
process_request,process_response
当用户发起请求的时候会依次经过所有的的中间件,这个时候的请求时process_request,最后到达views的函数中,views函数处理后,在依次穿过中间件,这个时候是process_response,最后返回给请求者。
上述截图中的中间件都是django中的,我们也可以自己定义一个中间件,我们可以自己写一个类,但是必须继承MiddlewareMixin
方法一:
需要导入
from django.utils.deprecation import MiddlewareMixin
方法二(推荐):在自己定义的中间件中把MiddlewareMixin这个类粘过来
class MiddlewareMixin(object): def __init__(self, get_response=None): self.get_response = get_response super(MiddlewareMixin, self).__init__() def __call__(self, request): response = None if hasattr(self, \'process_request\'): response = self.process_request(request) if not response: response = self.get_response(request) if hasattr(self, \'process_response\'): response = self.process_response(request, response) return response class RbacMiddleware(MiddlewareMixin): 方法。。。。。。
in views:
def index(request): print("view函数...") return HttpResponse("OK")
in Mymiddlewares.py:
from django.utils.deprecation import MiddlewareMixin from django.shortcuts import HttpResponse class Md1(MiddlewareMixin): def process_request(self,request): print("Md1请求") def process_response(self,request,response): print("Md1返回") return response class Md2(MiddlewareMixin): def process_request(self,request): print("Md2请求") #return HttpResponse("Md2中断") def process_response(self,request,response): print("Md2返回") return response
结果:
Md1请求
Md2请求
view函数...
Md2返回
Md1返回
注意:如果当请求到达请求2的时候直接不符合条件返回,即return HttpResponse("Md2中断"),程序将把请求直接发给中间件2返回,然后依次返回到请求者,结果如下: 返回Md2中断的页面,后台打印如下:
Md1请求 Md2请求 Md2返回 Md1返回
流程图如下:
process_view
process_view(self, request, callback, callback_args, callback_kwargs)
Mymiddlewares.py修改如下
from django.utils.deprecation import MiddlewareMixin from django.shortcuts import HttpResponse class Md1(MiddlewareMixin): def process_request(self,request): print("Md1请求") #return HttpResponse("Md1中断") def process_response(self,request,response): print("Md1返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): print("Md1view") class Md2(MiddlewareMixin): def process_request(self,request): print("Md2请求") return HttpResponse("Md2中断") def process_response(self,request,response): print("Md2返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): print("Md2view")
结果如下:
Md1请求
Md2请求
Md1view
Md2view
view函数...
Md2返回
Md1返回
下图进行分析上面的过程:
当最后一个中间的process_request到达路由关系映射之后,返回到中间件1的process_view,然后依次往下,到达views函数,最后通过process_response依次返回到达用户。
process_view可以用来调用视图函数:
class Md1(MiddlewareMixin): def process_request(self,request): print("Md1请求") #return HttpResponse("Md1中断") def process_response(self,request,response): print("Md1返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): # return HttpResponse("hello") response=callback(request,*callback_args,**callback_kwargs) return response
结果如下:
Md1请求 Md2请求 view函数... Md2返回 Md1返回
注意:process_view如果有返回值,会越过其他的process_view以及视图函数,但是所有的process_response都还会执行。、
process_exception
1
|
process_exception( self , request, exception) |
示例修改如下:
class Md1(MiddlewareMixin): def process_request(self,request): print("Md1请求") #return HttpResponse("Md1中断") def process_response(self,request,response): print("Md1返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): # return HttpResponse("hello") # response=callback(request,*callback_args,**callback_kwargs) # return response print("md1 process_view...") def process_exception(self): print("md1 process_exception...") class Md2(MiddlewareMixin): def process_request(self,request): print("Md2请求") # return HttpResponse("Md2中断") def process_response(self,request,response): print("Md2返回") return response def process_view(self, request, callback, callback_args, callback_kwargs): print("md2 process_view...") def process_exception(self): print("md1 process_exception...")
结果如下:
Md1请求
Md2请求
md1 process_view...
md2 process_view...
view函数...
Md2返回
Md1返回
流程图如下:
当views出现错误时:
将md2的process_exception修改如下:
def process_exception(self,request,exception): print("md2 process_exception...") return HttpResponse("error")
结果如下:
Md1请求
Md2请求
md1 process_view...
md2 process_view...
view函数...
md2 process_exception...
Md2返回
Md1返回
总结:
- 中间件是什么?
Django 中的中间件时一个类 包括四个方法, process_view,process_exception,priocess_request,process_response,process_template_response()
- 返回值注意
Django中最需要 注意的是process_request(self,request)的返回值,如果request方法没有返回值则继续向下执行,如果有返回值的话则从同级 的response返回,不执行后面的 request方法后views中的方法
- 做过什么:
- 用户认证
- 日志记录
- csrf
-cors跨域
- session
- 权限管理***
-缓存
客户端请求来了,中间件去缓存看看有没有数据,有直接返回给用户,没有再去逻辑层 执行视图函数
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