Django REST_framework框架 02

mixin類編寫視圖

將上一篇文章中的寫法進一步封裝簡化

urls

from app01 import views
urlpatterns = [
    ......
    url(r'^authors/$', views.AuthorView.as_view(), name="author"),
    url(r'^authors/(?P<pk>\d+)/$', views.AuthorDetailView.as_view(), name="detail_author"),
]

還要寫一個ModelSerializer，方法與上一篇博文中相同
views

from rest_framework import mixins
from rest_framework import generics

#GenericAPIView繼承了APIView
class AuthorView(mixins.ListModelMixin,    #查看全部
                 mixins.CreateModelMixin,  #添加
                 generics.GenericAPIView):
    queryset = Author.objects.all()
    serializer_class = AuthorModelSerializers

    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

class AuthorDetailView(mixins.DestroyModelMixin,   #刪除
                       mixins.RetrieveModelMixin,  #查看單條
                       mixins.UpdateModelMixin,    #更新
                       generics.GenericAPIView):
    queryset = Author.objects.all()
    serializer_class = AuthorModelSerializers

    def get(self, request, *args, **kwargs):
        return self.retrieve(request, *args, **kwargs)

    def put(self, request, *args, **kwargs):
        return self.update(request, *args, **kwargs)

    def delete(self, request, *args, **kwargs):
        return self.destroy(request, *args, **kwargs)

viewsets.ModelViewSet

這是最終封裝版本，關鍵在於讓兩條不一樣的url（帶pk值和不帶pk值）都匯聚到同一個視圖類中

urls.py:

url(r'^authors/$', views.AuthorView.as_view({"get":"list","post":"create"}),name="author"),
url(r'^authors/(?P<pk>\d+)$', views.AuthorView.as_view({
            'get': 'retrieve',
            'put': 'update',
            'patch': 'partial_update',
            'delete': 'destroy'
        }),name="detail_author"),

views.py:

from rest_framework import viewsets

class AuthorView(viewsets.ModelViewSet):
    queryset = Author.objects.all()
    serializer_class = AuthorModelSerializers

源碼解析

如下面這個url爲例子，咱們能夠看到這條url最大的變化就是as_view後面傳值了，所以要看看是如何處理的

url(r'^authors/$', views.AuthorView.as_view({"get": "list", "post": "create"}), name="author")

咱們須要看看此時的as_view是如何用一個視圖類處理兩條url的，首先尋找這個as_view方法在哪裏，事實上它已經不是原來的as_view方法了
AuthorView類-ModelViewSet類-GenericViewSet類-ViewSetMixin類

在ViewSetMixin類中找到as_view方法

def as_view(cls, actions=None, **initkwargs):
    ......
    return csrf_exempt(view)

找到同在ViewSetMixin類中的view：

def as_view(cls, actions=None, **initkwargs):
    ......
    def view(request, *args, **kwargs):
        ......
        for method, action in actions.items(): #循環actions{"get": "list", "post": "create"}
            handler = getattr(self, action)    #handler = self.list或handler = self.create
            setattr(self, method, handler)     #self.get = self.list或self.post = self.create
            ......
        return self.dispatch(request, *args, **kwargs)

Django啓動後的url就等同於下面的狀況，等待用戶訪問

url(r'^authors/$', ViewSetMixin.view({"get": "list", "post": "create"}), name="author")

---

用戶訪問開始後：
在views.APIView中找到self.dispatch：

class APIView(View):
    def dispatch(self, request, *args, **kwargs):
        try:
            ......
            # Get the appropriate handler method
            if request.method.lower() in self.http_method_names:
                handler = getattr(self, request.method.lower(), #此處的request.method.lower()是字符串，get或post
                                  self.http_method_not_allowed)
                #由於上面已經經過反射綁定self.get = self.list或self.post = self.create，
                #所以這裏：
                #handler = self.list或self.create
            else:
                handler = self.http_method_not_allowed

            response = handler(request, *args, **kwargs) #這裏去找self.list或self.create，將執行的結果返回給response

        self.response = self.finalize_response(request, response, *args, **kwargs)
        return self.response #將ListModelMixin處理後的結果返回給請求者

self.list或self.create在ModelViewSet類的父類mixins.ListModelMixin或mixins.CreateModelMixin中

class ModelViewSet(mixins.CreateModelMixin,
                   mixins.RetrieveModelMixin,
                   mixins.UpdateModelMixin,
                   mixins.DestroyModelMixin,
                   mixins.ListModelMixin,
                   GenericViewSet):
    """
    A viewset that provides default `create()`, `retrieve()`, `update()`,
    `partial_update()`, `destroy()` and `list()` actions.
    """
    pass

ListModelMixin類將數據處理並序列化後返回給APIView下的dispatch

class ListModelMixin(object):
    """
    List a queryset.
    """
    def list(self, request, *args, **kwargs):
        queryset = self.filter_queryset(self.get_queryset())

        page = self.paginate_queryset(queryset)
        if page is not None:
            serializer = self.get_serializer(page, many=True)
            return self.get_paginated_response(serializer.data)

        serializer = self.get_serializer(queryset, many=True)
        return Response(serializer.data)

思考：viewsets.ModelViewSet經過覆蓋APIView中同名的as_view來實現了新功能，若是有需求的話咱們也能夠經過覆蓋同名方法來實現新的功能，例如咱們能夠本身寫一個list方法來實現不一樣的需求

認證組件

#認證組件
self.perform_authentication(request)
#權限組件
self.check_permissions(request)
#頻率組件
self.check_throttles(request)

局部視圖認證

在app01.service.auth.py:

from rest_framework import exceptions
from rest_framework.authentication import BaseAuthentication

class TokenAuth(BaseAuthentication):
    def authenticate(self, request):
        token = request.GET.get("token")
        token_obj = Token.objects.filter(token=token).first()
        if not token_obj: #認證失敗拋錯，被源碼中的try捕獲
            raise exceptions.AuthenticationFailed("驗證失敗!")
        return token_obj.user, token_obj.token #須要返回一個元組

在views.py：

def get_random_str(user):
    import hashlib, time
    ctime = str(time.time())

    md5 = hashlib.md5(bytes(user, encoding="utf8"))
    md5.update(bytes(ctime, encoding="utf8"))

    return md5.hexdigest()

from django.http import JsonResponse

class loginView(APIView):
    authentication_classes = [TokenAuth]

    def post(self, request):
        res = {"code": 1000, "msg": None}

        user = request.data.get("user")
        pwd = request.data.get("pwd")

        user_obj = User.objects.filter(name=user, pwd=pwd).first()
        if not user_obj:
            res["code"] = 1001
            res["msg"] = "用戶名或密碼錯誤"

        else:
            token = get_random_str(user)
            Token.objects.update_or_create(user=user_obj, defaults={"token": token})
            res["token"] = token

        return JsonResponse(res, json_dumps_params={"ensure_ascii": False})

源碼解析

咱們知道在APIView類中能夠找到as_view，而此時的as_view又指向了父類View中的as_view，此時父類as_view又會return dispatch，所以咱們在APIView類中找到dispatch方法，從這裏開始看源碼的執行過程。

class APIView(View):
    def dispatch(self, request, *args, **kwargs):
        self.initial(request, *args, **kwargs) #這一步就是在處理認證、權限、頻率

↓

class APIView(View):        
    def initial(self, request, *args, **kwargs):
        self.perform_authentication(request) #認證組件
        self.check_permissions(request)      #權限組件
        self.check_throttles(request)        #訪問頻率組件

↓

class APIView(View):
    def perform_authentication(self, request):
        request.user

這個request是Request類的實例化對象，所以咱們要去Request下面去找user方法
↓

class Request(object):
    @property
    def user(self):

        if not hasattr(self, '_user'):
            with wrap_attributeerrors():
                self._authenticate() #調用user過程其實就是在執行這個方法
        return self._user

查看self._authenticate
↓

class Request(object):
    def _authenticate(self):
        for authenticator in self.authenticators: #循環包含着一個個認證類實例的列表，此時就是一個[TokenAuth(),]
            try:
                user_auth_tuple = authenticator.authenticate(self) #將視圖中的authenticate返回結果賦值給user_auth_tuple，此時傳進去的self是Request類的實例化對象
            except exceptions.APIException: #驗證失敗拋錯
                self._not_authenticated()
                raise

            if user_auth_tuple is not None: #若是不爲空
                self._authenticator = authenticator
                self.user, self.auth = user_auth_tuple #user_auth_tuple是個元祖，分紅了兩個變量，這兩個變量能夠爲下面的權限組件所利用
                return #認證成功後返回

self.authenticators是什麼？
往上走，發現構建request時傳進來的參數

class APIView(View):
    def initialize_request(self, request, *args, **kwargs):
        ......

        return Request(
            request,
            parsers=self.get_parsers(),
            authenticators=self.get_authenticators(), #在這裏
            negotiator=self.get_content_negotiator(),
            parser_context=parser_context
        )

點進去看看，發現就是self.authentication_classes循環的結果

def get_authenticators(self):
        """
        Instantiates and returns the list of authenticators that this view can use.
        """
        return [auth() for auth in self.authentication_classes] #列表解析式，循環的是咱們本身在視圖中寫的一個個認證類

所以可見，self.authenticators就是包含着一個個認證類實例對象的列表

authenticator.authenticate(self)是什麼意思？
咱們再回到_authenticate方法中看看這句話

authenticator.authenticate(self)

實例化對象調本身的方法是不須要傳self的，所以這是個形參，我要知道這個self是誰

那麼這個self是誰？
要往上一級一級找，上一級是_authenticate(self)，誰調用的？
找到user(self),誰調用的user(self)?

class APIView(View):
    def perform_authentication(self, request):
        request.user

request.user調的user，所以self就是這個新構建的request，這個request是Request類的實例化對象

GET訪問時加上數據庫中已有的一個token就能經過驗證
http://127.0.0.1:8000/books/?token=1a54a64ee1111738c5d8b7b5487e801b

全局視圖認證組件

若是咱們本身不設authentication_classes，那麼就會去父類APIView中找，裏面有這麼一段代碼

authentication_classes = api_settings.DEFAULT_AUTHENTICATION_CLASSES

api_settings是APISettings類的一個實例化對象

api_settings = APISettings(None, DEFAULTS, IMPORT_STRINGS)

api_settings.DEFAULT_AUTHENTICATION_CLASSES會去找settings.py中的REST_FRAMEWORK

所以咱們本身在settings.py設置這個REST_FRAMEWORK就能夠

REST_FRAMEWORK = {
    "DEFAULT_AUTHENTICATION_CLASSES": ["app01.utils.TokenAuth"]
}

["app01.utils.TokenAuth"]這個值是具體路徑，也能夠是元祖

若是某個視圖（好比Login）不但願它通過全局認證，那麼能夠在視圖類中添加一個authentication_classes = []便可