DAY18-Django之分页和中间件
2024-10-20 03:50:51
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) #把所有数据按10条一页分 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range（1,8） 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) #如果get请求的page为空，则使用默认值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())
自己写的low版：
from django.shortcuts import render,HttpResponse,redirect
from app01.models import Book
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
# Create your views here. def index(request):
#插入数据
# obj_list=[]
# for i in range(1,101):
# obj=Book(title='book%s'%i,price=i*i)
# obj_list.append(obj)
# Book.objects.bulk_create(obj_list)
# return HttpResponse("ok") book_list=Book.objects.all()
paginator=Paginator(book_list,5) currentPage=request.GET.get("page",1)
if not currentPage.isdigit() or currentPage=="":
currentPage=1
currentPage=int(currentPage)
if currentPage > paginator.num_pages:
currentPage=paginator.num_pages book_list=paginator.page(currentPage) start=currentPage-3
if start<2:
start=2
end=start+7
if end>paginator.num_pages:
end=paginator.num_pages
if end-7>2:
start=end-7
page_range=range(start,end) return render(request,"index.html",locals())
views.py
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title>Title</title>
<!-- 最新版本的 Bootstrap 核心 CSS 文件 -->
<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>
{% for book in book_list %}
<div>{{ book.title }}----->{{ book.price }}</div>
{% endfor %} <nav aria-label="Page navigation">
<ul class="pagination">
{% if currentPage == 1 %}
<li class="disabled">
{% else %}
<li>
{% endif %} <a href="?page={{ currentPage|add:-1 }}" aria-label="Previous">
<span aria-hidden="true">«</span>
</a>
</li>
{% if currentPage == 1 %}
<li class="active">
{% else %}
<li>
{% endif %} <a href="?page=1">1</a></li>
{% if start == 2 %}
<li><span class="hidden">...</span></li>
{% else %}
<li><span>...</span></li>
{% endif %} {% for num in page_range %}
{% if num == currentPage %}
<li class="active">
{% else %}
<li>
{% endif %}
<a href="?page={{ num }}">{{ num }}</a></li>
{% endfor %}
{% if end == paginator.num_pages %}
<li><span class="hidden">...</span></li>
{% else %}
<li><span>...</span></li>
{% endif %}
{% if currentPage == paginator.num_pages %}
<li class="active">
{% else %}
<li>
{% endif %} <a href="?page={{ paginator.num_pages }}">{{ paginator.num_pages }}</a></li>
{% if currentPage == paginator.num_pages %}
<li class="disabled">
{% else %}
<li>
{% endif %}
<a href="?page={{ currentPage|add:1 }}" aria-label="Next">
<span aria-hidden="true">»</span>
</a>
</li>
</ul>
</nav> </div>
</body>
</html>
index.html
自定义分页器
"""
分页组件使用示例： obj = Pagination(request.GET.get('page',1),len(USER_LIST),request.path_info)
page_user_list = USER_LIST[obj.start:obj.end]
page_html = obj.page_html() return render(request,'index.html',{'users':page_user_list,'page_html':page_html}) """ class Pagination(object): def __init__(self,current_page,all_count,base_url,per_page_num=2,pager_count=11):
"""
封装分页相关数据
:param current_page: 当前页
:param all_count: 数据库中的数据总条数
:param per_page_num: 每页显示的数据条数
:param base_url: 分页中显示的URL前缀
:param pager_count: 最多显示的页码个数
""" try:
current_page = int(current_page)
except Exception as e:
current_page = 1 if current_page <1:
current_page = 1 self.current_page = current_page self.all_count = all_count
self.per_page_num = per_page_num self.base_url = base_url # 总页码
all_pager, tmp = divmod(all_count, per_page_num)
if tmp:
all_pager += 1
self.all_pager = all_pager self.pager_count = pager_count
self.pager_count_half = int((pager_count - 1) / 2) @property
def start(self):
return (self.current_page - 1) * self.per_page_num @property
def end(self):
return self.current_page * self.per_page_num def page_html(self):
# 如果总页码 < 11个：
if self.all_pager <= self.pager_count:
pager_start = 1
pager_end = self.all_pager + 1
# 总页码 > 11
else:
# 当前页如果<=页面上最多显示11/2个页码
if self.current_page <= self.pager_count_half:
pager_start = 1
pager_end = self.pager_count + 1 # 当前页大于5
else:
# 页码翻到最后
if (self.current_page + self.pager_count_half) > self.all_pager:
pager_end = self.all_pager + 1
pager_start = self.all_pager - self.pager_count + 1
else:
pager_start = self.current_page - self.pager_count_half
pager_end = self.current_page + self.pager_count_half + 1 page_html_list = [] first_page = '<li><a href="%s?page=%s">首页</a></li>' % (self.base_url,1,)
page_html_list.append(first_page) if self.current_page <= 1:
prev_page = '<li class="disabled"><a href="#">上一页</a></li>'
else:
prev_page = '<li><a href="%s?page=%s">上一页</a></li>' % (self.base_url,self.current_page - 1,) page_html_list.append(prev_page) for i in range(pager_start, pager_end):
if i == self.current_page:
temp = '<li class="active"><a href="%s?page=%s">%s</a></li>' % (self.base_url,i, i,)
else:
temp = '<li><a href="%s?page=%s">%s</a></li>' % (self.base_url,i, i,)
page_html_list.append(temp) if self.current_page >= self.all_pager:
next_page = '<li class="disabled"><a href="#">下一页</a></li>'
else:
next_page = '<li><a href="%s?page=%s">下一页</a></li>' % (self.base_url,self.current_page + 1,)
page_html_list.append(next_page) last_page = '<li><a href="%s?page=%s">尾页</a></li>' % (self.base_url,self.all_pager,)
page_html_list.append(last_page) return ''.join(page_html_list)
自定义分页（葫芦版）
data = [] for i in range(1, 302):
tmp = {"id": i, "name": "alex-{}".format(i)}
data.append(tmp) print(data) def user_list(request): # user_list = data[0:10]
# user_list = data[10:20]
try:
current_page = int(request.GET.get("page"))
except Exception as e:
current_page = 1 per_page = 10 # 数据总条数
total_count = len(data)
# 总页码
total_page, more = divmod(total_count, per_page)
if more:
total_page += 1 # 页面最多显示多少个页码
max_show = 11
half_show = int((max_show-1)/2) if current_page <= half_show:
show_start = 1
show_end = max_show
else:
if current_page + half_show >= total_page:
show_start = total_page - max_show
show_end = total_page
else:
show_start = current_page - half_show
show_end = current_page + half_show # 数据库中获取数据
data_start = (current_page - 1) * per_page
data_end = current_page * per_page user_list = data[data_start:data_end] # 生成页面上显示的页码
page_html_list = []
# 加首页
first_li = '<li><a href="/user_list/?page=1">首页</a></li>'
page_html_list.append(first_li)
# 加上一页
if current_page == 1:
prev_li = '<li><a href="#">上一页</a></li>'
else:
prev_li = '<li><a href="/user_list/?page={}">上一页</a></li>'.format(current_page - 1)
page_html_list.append(prev_li)
for i in range(show_start, show_end+1):
if i == current_page:
li_tag = '<li class="active"><a href="/user_list/?page={0}">{0}</a></li>'.format(i)
else:
li_tag = '<li><a href="/user_list/?page={0}">{0}</a></li>'.format(i)
page_html_list.append(li_tag) # 加下一页
if current_page == total_page:
next_li = '<li><a href="#">下一页</a></li>'
else:
next_li = '<li><a href="/user_list/?page={}">下一页</a></li>'.format(current_page+1)
page_html_list.append(next_li) # 加尾页
page_end_li = '<li><a href="/user_list/?page={}">尾页</a></li>'.format(total_page)
page_html_list.append(page_end_li) page_html = "".join(page_html_list) return render(request, "user_list.html", {"user_list": user_list, "page_html": page_html})
稳扎稳打版
class Pagination(object):
def __init__(self, current_page, total_count, base_url, per_page=10, max_show=11):
"""
:param current_page: 当前页
:param total_count: 数据库中数据总数
:param per_page: 每页显示多少条数据
:param max_show: 最多显示多少页
"""
try:
current_page = int(current_page)
except Exception as e:
current_page = 1 self.current_page = current_page
self.total_count = total_count
self.base_url = base_url
self.per_page = per_page
self.max_show = max_show # 总页码
total_page, more = divmod(total_count, per_page)
if more:
total_page += 1 half_show = int((max_show - 1) / 2)
self.half_show = half_show
self.total_page = total_page @property
def start(self):
return (self.current_page - 1) * self.per_page @property
def end(self):
return self.current_page * self.per_page def page_html(self): if self.current_page <= self.half_show:
show_start = 1
show_end = self.max_show
else:
if self.current_page + self.half_show >= self.total_page:
show_start = self.total_page - self.max_show
show_end = self.total_page
else:
show_start = self.current_page - self.half_show
show_end = self.current_page + self.half_show # 生成页面上显示的页码
page_html_list = []
# 加首页
first_li = '<li><a href="{}?page=1">首页</a></li>'.format(self.base_url)
page_html_list.append(first_li)
# 加上一页
if self.current_page == 1:
prev_li = '<li><a href="#">上一页</a></li>'
else:
prev_li = '<li><a href="{0}?page={1}">上一页</a></li>'.format(self.base_url, self.current_page - 1)
page_html_list.append(prev_li)
for i in range(show_start, show_end + 1):
if i == self.current_page:
li_tag = '<li class="active"><a href="{0}?page={1}">{1}</a></li>'.format(self.base_url, i)
else:
li_tag = '<li><a href="{0}?page={1}">{1}</a></li>'.format(self.base_url, i)
page_html_list.append(li_tag) # 加下一页
if self.current_page == self.total_page:
next_li = '<li><a href="#">下一页</a></li>'
else:
next_li = '<li><a href="{0}?page={1}">下一页</a></li>'.format(self.base_url, self.current_page + 1)
page_html_list.append(next_li) # 加尾页
page_end_li = '<li><a href="{0}?page={1}">尾页</a></li>'.format(self.base_url, self.total_page)
page_html_list.append(page_end_li) return "".join(page_html_list)
封装保存版
def user_list(request):
pager = Pagination(request.GET.get("page"), len(data), request.path_info)
user_list = data[pager.start:pager.end]
page_html = pager.page_html()
return render(request, "user_list.html", {"user_list": user_list, "page_html": page_html})
Django内置分页
from django.shortcuts import render
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger L = []
for i in range(999):
L.append(i) def index(request):
current_page = request.GET.get('p') paginator = Paginator(L, 10)
# per_page: 每页显示条目数量
# count: 数据总个数
# num_pages:总页数
# page_range:总页数的索引范围，如: (1,10),(1,200)
# page: page对象
try:
posts = paginator.page(current_page)
# has_next 是否有下一页
# next_page_number 下一页页码
# has_previous 是否有上一页
# previous_page_number 上一页页码
# object_list 分页之后的数据列表
# number 当前页
# paginator paginator对象
except PageNotAnInteger:
posts = paginator.page(1)
except EmptyPage:
posts = paginator.page(paginator.num_pages)
return render(request, 'index.html', {'posts': posts})
内置分页view部分
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
</head>
<body>
<ul>
{% for item in posts %}
<li>{{ item }}</li>
{% endfor %}
</ul> <div class="pagination">
<span class="step-links">
{% if posts.has_previous %}
<a href="?p={{ posts.previous_page_number }}">Previous</a>
{% endif %}
<span class="current">
Page {{ posts.number }} of {{ posts.paginator.num_pages }}.
</span>
{% if posts.has_next %}
<a href="?p={{ posts.next_page_number }}">Next</a>
{% endif %}
</span> </div>
</body>
</html>
内置分页HTML部分
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
需要导入
from django.utils.deprecation import MiddlewareMixin
注意，自定义的中间件模块名称和存放位置也不用固定，也可以放到具体应用文件夹中.
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
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
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