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一、源码剖析
对于以上示例，你可以会有疑问，问什么配置上了一些类的属性就能有不同的效果呢？当然源码是有这些定制配置的，这里以PageNumberPagination分页进行说明，下面是PageNumberPagination的源码，可能稍微长，我们进行配置部分解读就好，其他部分和分页相关的逻辑这里就不过多介绍，解读部分请看注释：
class PageNumberPagination(BasePagination):
"""
A simple page number based style that supports page numbers as
query parameters. For example:
http://api.example.org/accounts/?page=4
http://api.example.org/accounts/?page=4&page_size=100
"""# The default page size.# Defaults to `None`, meaning pagination is disabled.
page_size = api_settings.PAGE_SIZE #每页显示个数配置，可以在setting中配置，也可以在类里，当前类>全局（settings）
django_paginator_class = DjangoPaginator # 本质使用django自带的分页组件
# Client can control the page using this query parameter.
page_query_param = 'page' # url中的页码key配置
page_query_description = _('A page number within the paginated result set.') # 描述
# Client can control the page size using this query parameter.# Default is 'None'. Set to eg 'page_size' to enable usage.
page_size_query_param = None # url中每页显示个数的key配置
page_size_query_description = _('Number of results to return per page.')
# Set to an integer to limit the maximum page size the client may request.# Only relevant if 'page_size_query_param' has also been set.
max_page_size = None # 最多显示个数配置
last_page_strings = ('last',)
template = 'rest_framework/pagination/numbers.html' # 渲染的模板
invalid_page_message = _('Invalid page.') # 页面不合法返回的信息，当然我们也可以自己定制
def paginate_queryset(self, queryset, request, view=None): # 获取分页数据
"""
Paginate a queryset if required, either returning a
page object, or `None` if pagination is not configured for this view.
"""
page_size = self.get_page_size(request) # 调用get_page_size 获取当前请求的每页显示数量
if not page_size:
return None
paginator = self.django_paginator_class(queryset, page_size)
page_number = request.query_params.get(self.page_query_param, 1)
if page_number in self.last_page_strings:
page_number = paginator.num_pages
try:
self.page = paginator.page(page_number)
except InvalidPage as exc:
msg = self.invalid_page_message.format(
page_number=page_number, message=six.text_type(exc)
)
raise NotFound(msg)
if paginator.num_pages > 1 and self.template is not None:
# The browsable API should display pagination controls.
self.display_page_controls = True
self.request = request
return list(self.page)
def get_paginated_response(self, data):
return Response(OrderedDict([
('count', self.page.paginator.count),
('next', self.get_next_link()),
('previous', self.get_previous_link()),
('results', data)
]))
def get_page_size(self, request):
if self.page_size_query_param:
try:
return _positive_int(
request.query_params[self.page_size_query_param],
strict=True,
cutoff=self.max_page_size
)
except (KeyError, ValueError):
passreturn self.page_size
def get_next_link(self):
if not self.page.has_next():
return None
url = self.request.build_absolute_uri()
page_number = self.page.next_page_number()
return replace_query_param(url, self.page_query_param, page_number)
def get_previous_link(self):
if not self.page.has_previous():
return None
url = self.request.build_absolute_uri()
page_number = self.page.previous_page_number()
if page_number == 1:
return remove_query_param(url, self.page_query_param)
return replace_query_param(url, self.page_query_param, page_number)
def get_html_context(self):
base_url = self.request.build_absolute_uri()
def page_number_to_url(page_number):
if page_number == 1:
return remove_query_param(base_url, self.page_query_param)
else:
return replace_query_param(base_url, self.page_query_param, page_number)
current = self.page.number
final = self.page.paginator.num_pages
page_numbers = _get_displayed_page_numbers(current, final)
page_links = _get_page_links(page_numbers, current, page_number_to_url)
return {
'previous_url': self.get_previous_link(),
'next_url': self.get_next_link(),
'page_links': page_links
}
def to_html(self):
template = loader.get_template(self.template)
context = self.get_html_context()
return template.render(context)
def get_schema_fields(self, view):
assert coreapi is not None, 'coreapi must be installed to use `get_schema_fields()`'assert coreschema is not None, 'coreschema must be installed to use `get_schema_fields()`'
fields = [
coreapi.Field(
name=self.page_query_param,
required=False,
location='query',
schema=coreschema.Integer(
title='Page',
description=force_text(self.page_query_description)
)
)
]
if self.page_size_query_param is not None:
fields.append(
coreapi.Field(
name=self.page_size_query_param,
required=False,
location='query',
schema=coreschema.Integer(
title='Page size',
description=force_text(self.page_size_query_description)
)
)
)
return fields
复制代码二、使用总结
虽然对于分页来说，django rest framework 给我们提供了多种分页，但是最为常用的还是第一种PageNumberPagination，推荐使用。
而第二种LimitOffsetPagination，使用场景是当数据量比较大时候，只关心其中某一部分数据，推荐使用。
CursorPagination类型分页相对于PageNumberPagination有点在于，它避免了人为在url中自己传入参数进行页面的刷新（因为url不规则），缺点也显而易见只能进行上下页的翻阅。
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