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2. Django REST Framework (DRF) Serialization & amp; Deserialization & amp; Data Validation
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Five, DRF model serializer ModelSerializer
1. Background
1. Create a request, post, and the user can directly create a piece of data by inputting json data
2. The update request, put, requires two types of data:
- The json data passed in by the user, which fields need to be updated.
- You need to go to the library to take out the instance that needs to be updated, and then update it.
Our current post creates and puts update requests. They are all database operations performed using the ORM framework in the views.py view function.
create request, post
# create class
def post(self, request):
# 1. Get the json parameter and convert it to the data type (dictionary) in python
try:
dic_data = json. loads(request. body)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
# Get the deserialized instance object
class_obj = ClassSerializer(data=dic_data)
# Validate the data
# Validation failed
if not class_obj.is_valid():
return JsonResponse(class_obj. errors, status=400)
# Create data, execute saql
miaoclass = MiaoClass.objects.create(**class_obj.validated_data)
# Perform data echo (serialization) on the created data
serializer = ClassSerializer(instance=miaoclass)
return JsonResponse(serializer.data, status=201)
Update request, put:
def put(self, request, pk):
# 1. It is necessary to verify whether pk exists in the database
# 2. Read project data from the database
try:
student_obj = MiaoStudent.objects.get(id=pk)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
# 3. Get the json parameter and convert it into a dictionary
try:
dic = json.loads(request.body)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
# 4. Serialization, converting the dictionary entered by the user into a serialized instance
serializer_obj=StudentSerializer(data=dic)
# 5. The serializer verifies the parameters passed in by the user
# is_valid() data validation
# serializer_obj.errors error message after verification
if not serializer_obj.is_valid():
return JsonResponse(serializer_obj. errors, status=400)
# 6. Update data and operate the database
student_obj.sname = serializer_obj.validated_data.get('sname')
student_obj.sgender = serializer_obj.validated_data.get('sgender')
student_obj.sid = serializer_obj.validated_data.get('sid')
student_obj.sscore = serializer_obj.validated_data.get('sscore')
student_obj.classid_id = serializer_obj.validated_data.get('classid_id')
student_obj. save()
# 7. Data display (not required). Convert the read item data into a dictionary
serializer = StudentSerializer(instance=student_obj)
return JsonResponse(serializer.data, status=201)
2. Serializer create method and update method
The above processing database operation is carried out in the views view function, now
Encapsulate the behavior of operating the database into the serializer class.
The post create creation operation is implemented through the serializer create method
The put update update operation is implemented through the serializer update method.
2.1 Serializer create method
Original post creation request
class StudentsView(View):
# query all data
def get(self, request):
# get list data
queryset = MiaoStudent. objects. all()
print(queryset)
serializer = StudentSerializer(instance=queryset, many=True)
return JsonResponse(serializer. data, safe=False)
# create data
def post(self, request):
# 1. Get the json parameter and convert it to the data type (dictionary) in python
try:
dic_data = json. loads(request. body)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
# Get the deserialized instance object
student_serializer_obj = StudentSerializer(data=dic_data)
# Validate the data
# Validation failed
if not student_serializer_obj.is_valid():
return JsonResponse(student_serializer_obj. errors, status=400)
# create data, execute saql
student=MiaoStudent.objects.create(**student_serializer_obj.validated_data)
# Perform data echo (serialization) on the created data
serializer = StudentSerializer(instance=student)
return JsonResponse(serializer.data, status=201)
1. Change the original code to create data
# create data, execute saql
student=MiaoStudent.objects.create(**student_serializer_obj.validated_data)
replace with
# create data, execute saql
# student=MiaoStudent.objects.create(**student_serializer_obj.validated_data)
# Operate the database through the serializer
student_serializer_obj. save()
# Perform data echo (serialization) on the created data
#serializer = StudentSerializer(instance=student)
return JsonResponse(student_serializer_obj.data, status=201)
When constructing the serializer object, only pass in the data= parameter.
# Get the deserialized instance object
student_serializer_obj = StudentSerializer(data=dic_data)
When the serializer calls the save method, it actually calls the create method in the serializer. (According to the parameters passed in when creating the object, it is judged whether to call the create method or the update method when executing the save method.
When building a serializer instance, only pass data= , and when calling save, the create method is called.
When building a serializer instance, pass data= and instance= at the same time, and when calling save, call the update method.
2. In the serializer, create the create method
def create(self, validated_data: dict):
project_obj = MiaoStudent.objects.create(**validated_data)
return project_obj
The operation of the database will be executed in the create method.
in:
- validated_data: dict is the obtained user input data after validation, which is a dictionary.
3. Save method keyword parameter passing
Execute the save method.
student_serializer_obj.save()
Which fields are entered by the user, and which fields are used when operating the database.
Implementation function:
Not only do I want to get the fields entered by the user, but I also need to add some additional fields that I want to add to the program.
able to pass
.save(keyword 1:"value 1",keyword 2:"value 2")
incoming.
The create method is used to obtain, and the validated user passes in validated_data, which is a dictionary. This dictionary contains the additional data we just passed in.
Example:
passed in when calling save
student_serializer_obj.save(address="Beijing",hobby="play")
Execute the create method to retrieve additional data.
def create(self, validated_data: dict):
address = validated_data. pop("address")
hobby = validated_data. pop("address")
project_obj = MiaoStudent.objects.create(**validated_data)
return project_obj
2.2 Serializer update method
In the views view, put the original code
def put(self, request, pk):
# 1. It is necessary to verify whether pk exists in the database
# 2. Read project data from the database
try:
student_obj = MiaoStudent.objects.get(id=pk)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
# 3. Get the json parameter and convert it into a dictionary
try:
dic = json.loads(request.body)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
# 4. Serialization, converting the dictionary entered by the user into a serialized instance
serializer_obj=StudentSerializer(data=dic)
# 5. The serializer verifies the parameters passed in by the user
# is_valid() data validation
# serializer_obj.errors error message after verification
if not serializer_obj.is_valid():
return JsonResponse(serializer_obj. errors, status=400)
# 6. Update data and operate the database
student_obj.sname = serializer_obj.validated_data.get('sname')
student_obj.sgender = serializer_obj.validated_data.get('sgender')
student_obj.sid = serializer_obj.validated_data.get('sid')
student_obj.sscore = serializer_obj.validated_data.get('sscore')
student_obj.classid_id = serializer_obj.validated_data.get('classid_id')
student_obj. save()
# 7. Data display (not required). Convert the read item data into a dictionary
serializer = StudentSerializer(instance=student_obj)
return JsonResponse(serializer.data, status=201)
1. View function: When creating a serialized instance, use data= , instance=
student_obj = MiaoStudent.objects.get(id=pk) dic = json.loads(request.body) serializer_obj = StudentSerializer(data=dic, instance=student_obj)
The overall code of the modified view function
class StudentsDetailView(View):
def get(self, request, pk):
# 1. It is necessary to verify whether pk exists in the database
# 2. Read project data from the database
try:
student_obj = MiaoStudent.objects.get(id=pk)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
serializer = StudentSerializer(instance=student_obj)
return JsonResponse(serializer.data)
def put(self, request, pk):
# 1. It is necessary to verify whether pk exists in the database
# 2. Read project data from the database
try:
student_obj = MiaoStudent.objects.get(id=pk)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
# 3. Get the json parameter and convert it into a dictionary
try:
dic = json.loads(request.body)
except Exception as e:
return JsonResponse({'msg': 'The parameter is wrong'}, status=400)
# 4. Serialization, converting the dictionary entered by the user into a serialized instance
# serializer_obj=StudentSerializer(data=dic)
serializer_obj = StudentSerializer(data=dic, instance=student_obj)
# 5. The serializer verifies the parameters passed in by the user
# is_valid() data validation
# serializer_obj.errors error message after verification
if not serializer_obj.is_valid():
return JsonResponse(serializer_obj. errors, status=400)
# 6. Update data and operate the database
# student_obj.sname = serializer_obj.validated_data.get('sname')
# student_obj.sgender = serializer_obj.validated_data.get('sgender')
# student_obj.sid = serializer_obj.validated_data.get('sid')
# student_obj.sscore = serializer_obj.validated_data.get('sscore')
# student_obj.classid_id = serializer_obj.validated_data.get('classid_id')
# student_obj. save()
serializer_obj. save()
# 7. Data display (not required). Convert the read item data into a dictionary
# serializer = StudentSerializer(instance=student_obj)
return JsonResponse(serializer_obj.data, status=201)
2. The update method in the serializer
def update(self, instance, validated_data: dict):
# for key, value in validated_data.items():
# setattr(instance, key, value)
# validated_data is the data passed in by the user after verification
instance.sname = validated_data.get('sname') or instance.sname
instance.sgender = validated_data.get('sgender') or instance.sgender
instance.sid = validated_data.get('sid') or instance.sid
instance.sage = validated_data.get('sage') or instance.sage
instance.sscore = validated_data.get('sscore') or instance.sscore
instance.classid_id = validated_data.get('classid_id') or instance.classid_id
instance. save()
return instance
- or is for processing when the value is empty
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