DJango REST framework之分页组件以及对源码的阅读

分页围绕三类

　　a. 分页看第n页， 每页显示的n条数据 PageNumberPagination
　　b. 在n个位置，向后查看n条数据 LimitOffsetPagination
　　c. 加密分页 上一页和下一页CursorPagination  用户不能随便输入页码，页码已被这个类加密 ，这个类做的好，它把当前页的最大的id和最小的id的记住，下次在分页的时候根据最大和最小id来，如果不加密的话，假如数据库数据非常多的话，用户万一从当前页直接输入“四九”页，这时候应该数据响应速度慢，MySQL服务器压力太大了。

举例：

表设计

from django.db import models


class UserGroup(models.Model):
    title = models.CharField(max_length=32)


class UserInfo(models.Model):
    user_type_choices = (
        (1, '普通用户'),
        (2, 'vip'),
        (3, 'svip'),
    )
    user_type = models.IntegerField(choices=user_type_choices)
    username = models.CharField(max_length=32, unique=True)
    password = models.CharField(max_length=64)
    group = models.ForeignKey('UserGroup', on_delete=models.CASCADE)
    roles = models.ManyToManyField('Role')


class UserToken(models.Model):
    user = models.OneToOneField(to='UserInfo', on_delete=models.CASCADE)
    token = models.CharField(max_length=64)


class Role(models.Model):
    title = models.CharField(max_length=32)

 路由：

from django.contrib import admin
from django.urls import path, re_path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    re_path('api/', include('api.urls')),
]

 分发：

from django.urls import path, re_path, include
from api import views

urlpatterns = [
    # 分页
    re_path('(?P<version>[v1|v2]+)/page1/$', views.Page1View.as_view()),
]

视图以及序列化

class PagerSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Role
        fields = '__all__'


from rest_framework.response import Response
from rest_framework.pagination import PageNumberPagination, LimitOffsetPagination, CursorPagination


class MyPageNumberPagination(PageNumberPagination):
    """
    http://api.example.org/accounts/?page=4
    http://api.example.org/accounts/?page=4&page_size=100
    """
    page_size = 2
    # 自己通过传参定制一页显示多少数据
    # http://127.0.0.1:8000/api/v1/page1/?page=2&size=3
    page_size_query_param = 'size'
    max_page_size = 5

    page_query_param = 'page'


class MyLimitOffsetPagination(LimitOffsetPagination):
    """
    http://api.example.org/accounts/?limit=100
    http://api.example.org/accounts/?offset=400&limit=100
    """
    default_limit = 2
    limit_query_param = 'limit'
    offset_query_param = 'offset'
    max_limit = 5


class MyCursorPagination(CursorPagination):
    """
    "next": "http://127.0.0.1:8000/api/v1/page1/?cursor=cD02",
    "previous": "http://127.0.0.1:8000/api/v1/page1/?cursor=cj0xJnA9NQ%3D%3D",
    """
    cursor_query_param = 'cursor'
    page_size = 2
    ordering = 'id'
    page_size_query_param = None
    max_page_size = None


class Page1View(APIView):
    def get(self, request, *args, **kwargs):
        roles = models.Role.objects.all()

        # pg = PageNumberPagination()
        # pg = MyPageNumberPagination()
        # pg = MyLimitOffsetPagination()
        pg = MyCursorPagination()

        # 在数据库中获取分页的数据
        pg_roles = pg.paginate_queryset(queryset=roles, request=request, view=self)
        # 对数据序列化
        ser = PagerSerializer(instance=pg_roles, many=True)

        # 返回两种方式
        # ret = ser.data
        # return Response(ret)
        # 帮我们做了上一页下一页的
        # "count": 8,
        # "next": "http://127.0.0.1:8000/api/v1/page1/?page=3&size=3",
        # "previous": "http://127.0.0.1:8000/api/v1/page1/?size=3",
        ret = pg.get_paginated_response(ser.data)
        return ret

全局也可配置：

REST_FRAMEWORK = {
    # 分页
    'PAGE_SIZE': 2
}

内置的分页类：

我觉得这个三个已经够用了。CursorPagination这个重要，而且涉及到了性能。