DRF开发避坑指南01

在当今快速发展的Web开发领域，Django REST Framework（DRF）以其强大的功能和灵活性成为了众多开发者的首选。然而，错误的使用方法不仅会导致项目进度延误，还可能影响性能和安全性。本文将从我个人本身遇到的相关坑来给大家避坑。

一、API性能优化

坑：响应太慢！！！！！！

import os
from django_filters.rest_framework import DjangoFilterBackend

from rest_framework import viewsets
from rest_framework import filters
from rest_framework import permissions, authentication
from rest_framework.decorators import action
from rest_framework_simplejwt.authentication import JWTAuthentication

from utils.rest_framework_util.pagination import CommonPagination
from utils.rest_framework_util.response import rtn_success_info, rtn_error_info
from utils.rest_framework_util.excel_util import ExcelUtil, write_excel_file
from utils.utils import get_current_time_format
from utils.oss.tx_upload import CommonUpload
from drf_yasg import openapi

__all__ = {
    "CommonViewSet",
    "CommonUserViewSet"
}

from drf_yasg.utils import swagger_auto_schema
from drf_yasg import openapi

class CommonViewSet(viewsets.ModelViewSet):
    permission_classes = ()
    authentication_classes = ()

    filter_backends = [ DjangoFilterBackend, filters.SearchFilter]

    search_fields = ["id"]
    save_export_folder = "static/save_export/"
    pagination_class = CommonPagination

    def list(self, request, *args, **kwargs):
        queryset = self.filter_queryset(self.get_queryset())
        len_model = len(queryset)
        page = self.paginate_queryset(queryset)
        if page is not None:
            serializer = self.get_serializer(page, many=True)
            response_data = {
                "total": len_model,
                "list": serializer.data
            }
            return rtn_success_info(response_data, msg="查询数据成功")
        serializer = self.get_serializer(queryset, many=True)
        return rtn_success_info(serializer.data)

    def retrieve(self, request, *args, **kwargs):
        instance = self.get_object()
        serializer = self.get_serializer(instance)
        return rtn_success_info(serializer.data)

    def update(self, request, *args, **kwargs):
        """
        put 修改
        """
        try:
            partial = kwargs.pop('partial', False)
            instance = self.get_object()
            serializer = self.get_serializer(instance, data=request.data, partial=partial)
            serializer.is_valid(raise_exception=True)
            self.perform_update(serializer)

            if getattr(instance, '_prefetched_objects_cache', None):
                # If 'prefetch_related' has been applied to a queryset, we need to
                # forcibly invalidate the prefetch cache on the instance.
                instance._prefetched_objects_cache = {}

            return rtn_success_info(serializer.data, msg='修改数据成功')
        except Exception as e:
            return rtn_error_info(msg=e)

    def destroy(self, request, *args, **kwargs):
        instance = self.get_object()
        self.perform_destroy(instance)
        return rtn_success_info(msg="数据删除成功")

    def perform_destroy(self, instance):
        instance.delete()

    def create(self, request, *args, **kwargs):
        serializer = self.get_serializer(data=request.data)
        serializer.is_valid(raise_exception=True)
        self.perform_create(serializer)
        return rtn_success_info(serializer.data, msg="创建数据成功")

    @action(detail=False, methods=['POST'])
    def data_import(self, request, *args, **kwargs):
        response_data_list = []
        file = request.FILES.get("file", None)
        if file is None:
            return rtn_error_info("需要传入file文件")
        else:
            title_list, data_list = ExcelUtil(file).read_data()
            serializer_class = self.get_serializer_class()
            model = serializer_class.Meta.model
            try:
                if model is not None:
                    model.objects.create()
                    for create_data in data_list:
                        response_data = {}
                        for index_, title in enumerate(title_list):
                            response_data[title] = create_data[index_]
                        if response_data.get('id', None) is not None:
                            response_data.pop("id")
                        serializer = self.get_serializer(data=response_data)
                        if serializer.is_valid():
                            # 创建
                            self.perform_create(serializer)
            except Exception as e:
                return rtn_error_info(f"数据导入失败:{e}")
            response_data_list = data_list
        return rtn_success_info(data=response_data_list, msg='导入数据成功')

    @action(detail=False, methods=['POST'])
    def data_export(self, request, *args, **kwargs):
        id_list = request.data.get('ids', None)
        queryset = self.get_queryset()
        row_data_list = []
        is_first = False
        title_list = []
        title = ""
        for data in queryset:
            title = data.__class__.__name__
            if not is_first:
                data_list = []
                for data_meta in data._meta.fields:
                    data_list.append(data_meta.name)
                    title_list.append(data_meta.name)
                row_data_list.append(data_list)  # title
                is_first = True
                break

        for value_data in queryset.values():
            data_info = []
            if id_list is not None:
                for id_ in id_list:
                    if int(value_data['id']) == int(id_):
                        for title in title_list:
                            data_info.append(value_data[title])
            else:
                for title in title_list:
                    data_info.append(value_data[title])
            if len(data_info) > 0:
                row_data_list.append(data_info)
        excel_file_name = f"{title}_{get_current_time_format('%Y_%m_%d_%H_%M_%S')}.xlsx"
        if not os.path.exists(self.save_export_folder):
            os.makedirs(self.save_export_folder)
        write_excel_file(row_data_list, f"{self.save_export_folder}{excel_file_name}")
        if os.path.exists(f"{self.save_export_folder}{excel_file_name}"):
            url = CommonUpload().cos_upload_file(f"{self.save_export_folder}{excel_file_name}")
            data = {
                'excel_url': url
            }
            return rtn_success_info(data, '导出成功')
        return rtn_error_info("导出失败")


class CommonUserViewSet(CommonViewSet):
    """带用户权限的ViewSet

    Args:
        viewsets (_type_): _description_

    Returns:
        _type_: _description_
    """

    permission_classes = [permissions.IsAuthenticated]
    authentication_classes = [JWTAuthentication, authentication.SessionAuthentication,
                              authentication.BasicAuthentication]

    def create(self, request, *args, **kwargs):
        data = request.data
        data["user"] = request.user.id
        serializer = self.get_serializer(data=data)
        serializer.is_valid(raise_exception=True)
        self.perform_create(serializer)
        return rtn_success_info(serializer.data, msg="创建数据成功")

    def list(self, request, *args, **kwargs):
        queryset = self.filter_queryset(self.get_queryset())
        len_model = len(queryset)
        page = self.paginate_queryset(queryset)
        if page is not None:
            serializer = self.get_serializer(page, many=True)
            response_data = {
                "total": len_model,
                "list": serializer.data
            }
            return rtn_success_info(response_data, msg="查询数据成功")
        serializer = self.get_serializer(queryset, many=True)
        return rtn_success_info(serializer.data)

以这块代码为例，大家会发现一个问题，虽然都封装了ViewSet，但是他的响应速度比之前慢很多，原因何在，问题就出现在len_model = len(queryset)上，因为当前的len(queryset)会遍历每一个model，导致性能缓慢，正确的修改方式是使用queryset.count()，会大幅度的提高性能，直接获取里面的变量。
图片

二、复杂权限管理
针对于这类的权限管理，其实DRF也给咱们弄好了，但是基于实际业务场景的复杂性，本人也提供给大家一个参考的可定制化的代码！
1.通过定制通用类的permissions

class CommonUserViewSet(CommonViewSet):
    """带用户权限的ViewSet

    Args:
        viewsets (_type_): _description_

    Returns:
        _type_: _description_
    """

    permission_classes = [permissions.IsAuthenticated]
    authentication_classes = [JWTAuthentication, authentication.SessionAuthentication,
                              authentication.BasicAuthentication]
 ``
类似这个，这个是用于基础的认证，比方说用户需要登陆才能确认的，使用这个比较方便。
![在这里插入图片描述](https://i-blog.csdnimg.cn/direct/07b878dcf2d641b79e9700d6a8ade683.png)


2.特定用户
这类的需求，可以通过获取self.request.user来判断，其中可以通过获取用户是否为超级用户，以及username等判断，大大提高drf的灵活性！

![在这里插入图片描述](https://i-blog.csdnimg.cn/direct/8ddab551e10942f7a1b7ebc0d0dd9686.png)

最后，大家还遇到哪些坑，也可以分享在评论区中，大家一起排雷，祝大家春节喜乐！觉得有用的话可以分享以及关注哈！