django rest framework post请求过程剖析
class ItemsModelViewset(BaseView): ''' create: 创建项目 retrieve: 查询项目信息 list： 查询所有项目信息 ''' queryset = ItemsModel.objects.all() permission_classes = (IsAuthenticated,) authentication_classes = (JSONWebTokenAuthentication, authentication.SessionAuthentication) def get_serializer_class(self): if self.action == "retrieve": return ItemsModelDetailSerializer elif self.action == "create": return ItemsModelDetailSerializer return ItemsModelDetailSerializer
这里的BaseView继承了viewsets.ModelViewSet类
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
在viewsets.ModelViewSet类中继承了mixins.CreateModelMixin, mixins.RetrieveModelMixin，mixins.UpdateModelMixin, mixins.DestroyModelMixin, mixins.ListModelMixin,GenericViewSet 这几个类分别有创建方法，查看详情方法，更新方法，删除方法，查看所有方法，分别对应post,get,put,delete,get方法，GenericViewSet是视图基类
在mixins.CreateModelMixin类中
class CreateModelMixin: """ Create a model instance. """ def create(self, request, *args, **kwargs): serializer = self.get_serializer(data=request.data) serializer.is_valid(raise_exception=True) self.perform_create(serializer) headers = self.get_success_headers(serializer.data) return Response(serializer.data, status=status.HTTP_201_CREATED, headers=headers) def perform_create(self, serializer): serializer.save() def get_success_headers(self, data): try: return {'Location': str(data[api_settings.URL_FIELD_NAME])} except (TypeError, KeyError): return {}
这里self.get_serializer(data=request.data)获取的是视图中get_serializer_class(self)方法获取的serializer类
serializer.save()调用的是rest_framework.serializers.BaseSerializer类的save()方法
def save(self, **kwargs): assert not hasattr(self, 'save_object'), ( 'Serializer `%s.%s` has old-style version 2 `.save_object()` ' 'that is no longer compatible with REST framework 3. ' 'Use the new-style `.create()` and `.update()` methods instead.' % (self.__class__.__module__, self.__class__.__name__) ) assert hasattr(self, '_errors'), ( 'You must call `.is_valid()` before calling `.save()`.' ) assert not self.errors, ( 'You cannot call `.save()` on a serializer with invalid data.' ) # Guard against incorrect use of `serializer.save(commit=False)` assert 'commit' not in kwargs, ( "'commit' is not a valid keyword argument to the 'save()' method. " "If you need to access data before committing to the database then " "inspect 'serializer.validated_data' instead. " "You can also pass additional keyword arguments to 'save()' if you " "need to set extra attributes on the saved model instance. " "For example: 'serializer.save(owner=request.user)'.'" ) assert not hasattr(self, '_data'), ( "You cannot call `.save()` after accessing `serializer.data`." "If you need to access data before committing to the database then " "inspect 'serializer.validated_data' instead. " ) validated_data = dict( list(self.validated_data.items()) + list(kwargs.items()) ) if self.instance is not None: self.instance = self.update(self.instance, validated_data) assert self.instance is not None, ( '`update()` did not return an object instance.' ) else: self.instance = self.create(validated_data) assert self.instance is not None, ( '`create()` did not return an object instance.' ) return self.instance
当instance为空的时候，则调用rest_framework.ModelSerializer.create方法
def create(self, validated_data): """ We have a bit of extra checking around this in order to provide descriptive messages when something goes wrong, but this method is essentially just: return ExampleModel.objects.create(**validated_data) If there are many to many fields present on the instance then they cannot be set until the model is instantiated, in which case the implementation is like so: example_relationship = validated_data.pop('example_relationship') instance = ExampleModel.objects.create(**validated_data) instance.example_relationship = example_relationship return instance The default implementation also does not handle nested relationships. If you want to support writable nested relationships you'll need to write an explicit `.create()` method. """ raise_errors_on_nested_writes('create', self, validated_data) ModelClass = self.Meta.model # Remove many-to-many relationships from validated_data. # They are not valid arguments to the default `.create()` method, # as they require that the instance has already been saved. info = model_meta.get_field_info(ModelClass) many_to_many = {} for field_name, relation_info in info.relations.items(): if relation_info.to_many and (field_name in validated_data): many_to_many[field_name] = validated_data.pop(field_name) try: instance = ModelClass._default_manager.create(**validated_data) except TypeError: tb = traceback.format_exc() msg = ( 'Got a `TypeError` when calling `%s.%s.create()`. ' 'This may be because you have a writable field on the ' 'serializer class that is not a valid argument to ' '`%s.%s.create()`. You may need to make the field ' 'read-only, or override the %s.create() method to handle ' 'this correctly.\nOriginal exception was:\n %s' % ( ModelClass.__name__, ModelClass._default_manager.name, ModelClass.__name__, ModelClass._default_manager.name, self.__class__.__name__, tb ) ) raise TypeError(msg) # Save many-to-many relationships after the instance is created. if many_to_many: for field_name, value in many_to_many.items(): field = getattr(instance, field_name) field.set(value) return instance
这里instance = ModelClass._default_manager.create(**validated_data) 这里的ModelClass类是django.db.models.base.ModelBase类，_default_manager方法调用了django.db.models.options.Options类的default_manager方法
def default_manager(self): default_manager_name = self.default_manager_name if not default_manager_name and not self.local_managers: # Get the first parent's default_manager_name if there's one. for parent in self.model.mro()[1:]: if hasattr(parent, '_meta'): default_manager_name = parent._meta.default_manager_name break if default_manager_name: try: return self.managers_map[default_manager_name] except KeyError: raise ValueError( "%s has no manager named %r" % ( self.object_name, default_manager_name, ) ) if self.managers: return self.managers[0]
这里调用了Options类的managers方法
def managers(self): managers = [] seen_managers = set() bases = (b for b in self.model.mro() if hasattr(b, '_meta')) for depth, base in enumerate(bases): for manager in base._meta.local_managers: if manager.name in seen_managers: continue manager = copy.copy(manager) manager.model = self.model seen_managers.add(manager.name) managers.append((depth, manager.creation_counter, manager)) return make_immutable_fields_list( "managers", (m[2] for m in sorted(managers)), )
在这里self.model是指的类本身，base._meta指的是类的实例化对象，通过mro获取类的所有子类，然后再通过._meta(类的实例化对象)调用Options实例的local_managers属性
通过查看local_managers的来源可以发现是通过Options类的add_manager方法添加的，然后发现在django.db.models.BaseManager类的contribute_to_class方法中有调用
def contribute_to_class(self, model, name): self.name = self.name or name self.model = model setattr(model, name, ManagerDescriptor(self)) model._meta.add_manager(self)
然后发现在django.db.models.base.ModelBase类的add_to_class方法中有调用，当django.db.models.base.ModelBase类在创建的时候就会调用add_to_class方法，详情如下
def __new__(cls, name, bases, attrs, **kwargs): super_new = super().__new__ # Also ensure initialization is only performed for subclasses of Model # (excluding Model class itself). parents = [b for b in bases if isinstance(b, ModelBase)] if not parents: return super_new(cls, name, bases, attrs) # Create the class. module = attrs.pop('__module__') new_attrs = {'__module__': module} classcell = attrs.pop('__classcell__', None) if classcell is not None: new_attrs['__classcell__'] = classcell attr_meta = attrs.pop('Meta', None) # Pass all attrs without a (Django-specific) contribute_to_class() # method to type.__new__() so that they're properly initialized # (i.e. __set_name__()). contributable_attrs = {} for obj_name, obj in list(attrs.items()): if _has_contribute_to_class(obj): contributable_attrs[obj_name] = obj else: new_attrs[obj_name] = obj new_class = super_new(cls, name, bases, new_attrs, **kwargs) abstract = getattr(attr_meta, 'abstract', False) meta = attr_meta or getattr(new_class, 'Meta', None) base_meta = getattr(new_class, '_meta', None) app_label = None # Look for an application configuration to attach the model to. app_config = apps.get_containing_app_config(module) if getattr(meta, 'app_label', None) is None: if app_config is None: if not abstract: raise RuntimeError( "Model class %s.%s doesn't declare an explicit " "app_label and isn't in an application in " "INSTALLED_APPS." % (module, name) ) else: app_label = app_config.label new_class.add_to_class('_meta', Options(meta, app_label)) if not abstract: new_class.add_to_class( 'DoesNotExist', subclass_exception( 'DoesNotExist', tuple( x.DoesNotExist for x in parents if hasattr(x, '_meta') and not x._meta.abstract ) or (ObjectDoesNotExist,), module, attached_to=new_class)) new_class.add_to_class( 'MultipleObjectsReturned', subclass_exception( 'MultipleObjectsReturned', tuple( x.MultipleObjectsReturned for x in parents if hasattr(x, '_meta') and not x._meta.abstract ) or (MultipleObjectsReturned,), module, attached_to=new_class)) if base_meta and not base_meta.abstract: # Non-abstract child classes inherit some attributes from their # non-abstract parent (unless an ABC comes before it in the # method resolution order). if not hasattr(meta, 'ordering'): new_class._meta.ordering = base_meta.ordering if not hasattr(meta, 'get_latest_by'): new_class._meta.get_latest_by = base_meta.get_latest_by is_proxy = new_class._meta.proxy # If the model is a proxy, ensure that the base class # hasn't been swapped out. if is_proxy and base_meta and base_meta.swapped: raise TypeError("%s cannot proxy the swapped model '%s'." % (name, base_meta.swapped)) # Add remaining attributes (those with a contribute_to_class() method) # to the class. for obj_name, obj in contributable_attrs.items(): new_class.add_to_class(obj_name, obj) # All the fields of any type declared on this model new_fields = chain( new_class._meta.local_fields, new_class._meta.local_many_to_many, new_class._meta.private_fields ) field_names = {f.name for f in new_fields} # Basic setup for proxy models. if is_proxy: base = None for parent in [kls for kls in parents if hasattr(kls, '_meta')]: if parent._meta.abstract: if parent._meta.fields: raise TypeError( "Abstract base class containing model fields not " "permitted for proxy model '%s'." % name ) else: continue if base is None: base = parent elif parent._meta.concrete_model is not base._meta.concrete_model: raise TypeError("Proxy model '%s' has more than one non-abstract model base class." % name) if base is None: raise TypeError("Proxy model '%s' has no non-abstract model base class." % name) new_class._meta.setup_proxy(base) new_class._meta.concrete_model = base._meta.concrete_model else: new_class._meta.concrete_model = new_class # Collect the parent links for multi-table inheritance. parent_links = {} for base in reversed([new_class] + parents): # Conceptually equivalent to `if base is Model`. if not hasattr(base, '_meta'): continue # Skip concrete parent classes. if base != new_class and not base._meta.abstract: continue # Locate OneToOneField instances. for field in base._meta.local_fields: if isinstance(field, OneToOneField): related = resolve_relation(new_class, field.remote_field.model) parent_links[make_model_tuple(related)] = field # Track fields inherited from base models. inherited_attributes = set() # Do the appropriate setup for any model parents. for base in new_class.mro(): if base not in parents or not hasattr(base, '_meta'): # Things without _meta aren't functional models, so they're # uninteresting parents. inherited_attributes.update(base.__dict__) continue parent_fields = base._meta.local_fields + base._meta.local_many_to_many if not base._meta.abstract: # Check for clashes between locally declared fields and those # on the base classes. for field in parent_fields: if field.name in field_names: raise FieldError( 'Local field %r in class %r clashes with field of ' 'the same name from base class %r.' % ( field.name, name, base.__name__, ) ) else: inherited_attributes.add(field.name) # Concrete classes... base = base._meta.concrete_model base_key = make_model_tuple(base) if base_key in parent_links: field = parent_links[base_key] elif not is_proxy: attr_name = '%s_ptr' % base._meta.model_name field = OneToOneField( base, on_delete=CASCADE, name=attr_name, auto_created=True, parent_link=True, ) if attr_name in field_names: raise FieldError( "Auto-generated field '%s' in class %r for " "parent_link to base class %r clashes with " "declared field of the same name." % ( attr_name, name, base.__name__, ) ) # Only add the ptr field if it's not already present; # e.g. migrations will already have it specified if not hasattr(new_class, attr_name): new_class.add_to_class(attr_name, field) else: field = None new_class._meta.parents[base] = field else: base_parents = base._meta.parents.copy() # Add fields from abstract base class if it wasn't overridden. for field in parent_fields: if (field.name not in field_names and field.name not in new_class.__dict__ and field.name not in inherited_attributes): new_field = copy.deepcopy(field) new_class.add_to_class(field.name, new_field) # Replace parent links defined on this base by the new # field. It will be appropriately resolved if required. if field.one_to_one: for parent, parent_link in base_parents.items(): if field == parent_link: base_parents[parent] = new_field # Pass any non-abstract parent classes onto child. new_class._meta.parents.update(base_parents) # Inherit private fields (like GenericForeignKey) from the parent # class for field in base._meta.private_fields: if field.name in field_names: if not base._meta.abstract: raise FieldError( 'Local field %r in class %r clashes with field of ' 'the same name from base class %r.' % ( field.name, name, base.__name__, ) ) else: field = copy.deepcopy(field) if not base._meta.abstract: field.mti_inherited = True new_class.add_to_class(field.name, field) # Copy indexes so that index names are unique when models extend an # abstract model. new_class._meta.indexes = [copy.deepcopy(idx) for idx in new_class._meta.indexes] if abstract: # Abstract base models can't be instantiated and don't appear in # the list of models for an app. We do the final setup for them a # little differently from normal models. attr_meta.abstract = False new_class.Meta = attr_meta return new_class new_class._prepare() new_class._meta.apps.register_model(new_class._meta.app_label, new_class) return new_class
回过头来看contribute_to_class方法 model._meta.add_manager(self)这里把他自己的实例化对象传进去
