django相关操作

Django内置序列化组件

我们在学习Django内置序列化组件之前需要知道的一点是：前后端分离的项目，它的视图函数只需要返回json格式的数据即可

from django.http import JsonResponse
1.不适用序列化组件
JsonResponse发送到前端的数据是以字典形式发送的，所以正常情况下如果我们想将数据以json格式通过JsonResponse发送到前端需要将数据转为字典格式
eg:
    def ad_set_func(request):
        book_queryset = models.Book.objects.all()
        data_dict = {}
        for book_obj in book_queryset:
            temp_dict = {}
            temp_dict['pk'] = book_obj.pk
            temp_dict['name'] = book_obj.name
            temp_dict['price'] = book_obj.price
            data_dict[book_obj.pk] = temp_dict
        return JsonResponse(data_dict)
    
2.使用序列化组件(django自带的)
    def ad_set_func(request):
        book_queryset = models.Book.objects.all()
        # 导入内置的序列化模块
        from django.core import serializers
        # 调用该模块下的方法，第一个参数是我们希望以什么样的方式序列化数据
        res = serializers.serialize('json', book_queryset)
        return HttpResponse(res)
    
注意：无论我们以哪种方式传json数据，汉字都会变成二进制编码，需要我们自己解码

批量操作数据

需求：现在有一张books表，需要往该表中插入10万条数据
1.使用for循环
    def insert_data(request):
        for i in range(1, 100000):
            models.Books.objects.create(name='第%s本书' % i)
        book_queryset = models.Books.objects.all()
        return render(request, 'datapage.html', locals())
    使用for循环往表中批量插数据速度会非常慢，数据量小的情况下还好，数据量一旦很大就会很慢
    
2.使用ORM提供的批量插入操作 bulk_create()
    def insert_data(request):
        book_obj_list = []  # 也可以使用列表生成式
        for i in range(1, 100000):
            book_obj = models.Book01(name='第%s本书' % i)  # 单纯的用类名加括号产生对象
            book_obj_list.append(book_obj)
        models.Book01.objects.bulk_create(book_obj_list)  # 使用ORM提供的批量插入操作
        book_queryset = models.Books.objects.all()
        return render(request, 'datapage.html', locals())

自定义分页器的使用

django自带分页器模块但是使用起来很麻烦 所以我们自己封装了一个，我们自己封装的模块可以创建一个自定义的py文件用来存储

class Pagination(object):
    def __init__(self, current_page, all_count, 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 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.all_count = all_count
        self.per_page_num = per_page_num
 
        # 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)
        
        if current_page > all_pager:
            current_page = 1
            
        self.current_page = current_page
 
    @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 = []
        # 添加前面的nav和ul标签
        page_html_list.append('''
                    <nav aria-label='Page navigation>'
                    <ul class='pagination'>
                ''')
        first_page = '<li><a href="?page=%s">首页</a></li>' % (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="?page=%s">上一页</a></li>' % (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="?page=%s">%s</a></li>' % (i, i,)
            else:
                temp = '<li><a href="?page=%s">%s</a></li>' % (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="?page=%s">下一页</a></li>' % (self.current_page + 1,)
        page_html_list.append(next_page)
 
        last_page = '<li><a href="?page=%s">尾页</a></li>' % (self.all_pager,)
        page_html_list.append(last_page)
        input_page = '<li><form action="" method="post"><input type="text" name="page"><input type="submit"></form></li>'
        page_html_list.append(input_page)
        # 尾部添加标签
        page_html_list.append('''
                                           </nav>
                                           </ul>
                                       ''')
        return ''.join(page_html_list)
    
    
后端使用
     def get_book(request):
           book_list = models.Book.objects.all()
           if request.method == 'POST':
               current_page = request.POST.get('page')
           else:
               current_page = request.GET.get("page", 1)
           all_count = book_list.count()
           page_obj = Pagination(current_page=current_page,all_count=all_count,per_page_num=10)
           page_queryset = book_list[page_obj.start:page_obj.end]
           return render(request,'booklist.html',locals())
    
前端使用
    <div class="container">
    <div class="row">
        <div class="col-md-8 col-md-offset-2">
            {% for book in page_queryset %}
            <p>{{ book.title }}</p>
            {% endfor %}
            {{ page_obj.page_html|safe }}
        </div>
    </div>
</div>