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JSONField in serializers – Django REST Framework

Last Updated : 22 Mar, 2022
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In Django REST Framework the very concept of Serializing is to convert DB data to a datatype that can be used by javascript. Every serializer comes with some fields (entries) which are going to be processed. For example if you have a class with name Employee and its fields as Employee_id, Employee_name, is_admin, etc. Then, you would need AutoField, CharField and BooleanField for storing and manipulating data through Django. Similarly, serializer also works with same principle and has fields that are used to create a serializer. This article revolves around JSONField in Serializers in Django REST Framework.


JSONField is basically a field class that validates that the incoming data structure consists of valid JSON primitives. In its alternate binary mode, it will represent and validate JSON-encoded binary strings. It has the following arguments –

  • binary – If set to True then the field will output and validate a JSON encoded string, rather than a primitive data structure. Defaults to False.
  • encoder – Use this JSON encoder to serialize input object. Defaults to None.

Syntax – 

field_name = serializers.JSONField(*args, **kwargs)

How to use JSONField in Serializers ?

To explain the usage of JSONField, let’s use the same project setup from – How to Create a basic API using Django Rest Framework ?. Now that you have a file called serializers in your project, let’s create a serializer with JSONField as the field. 


# import serializer from rest_framework
from rest_framework import serializers
class Geeks(object):
    def __init__(self, json_data):
        self.json_data = json_data
# create a serializer
class GeeksSerializer(serializers.Serializer):
    # initialize fields
    json_data = serializers.JSONField()

Now let us create some objects and try serializing them and check if they are actually working, Run, –

Python shell

Now, run following python commands in the shell

# create a json object
>>> import json
>>> x = json.dumps({"name":"Naveen", "Age":"21"})
>>> x
'{"name": "Naveen", "Age": "21"}'

# import everything from serializers
>>> from apis.serializers import *

# create a object of type Geeks
>>> obj = Geeks(x)

# serialize the object
>>> serializer = GeeksSerializer(obj)

# print serialized data
{'json_data': '{"name": "Naveen", "Age": "21"}'}

Here is the output of all these operations on terminal – jsonfield-in-serializers-Django-REST-Framework

Validation on JSONField

Note that prime motto of these fields is to impart validations, such as JSONField validates the data to JSON only. Let’s check if these validations are working or not –

# Create a dictionary and add invalid values
>>> data = {}
>>> data['json_data'] = x

# dictionary created
>>> data
{'json_data': '{"name": "Naveen", "Age": "21"}'}

# deserialize the data
>>> serializer = GeeksSerializer(data=data)

# check if data is valid
>>> serializer.is_valid()

# check the errors
>>> serializer.errors

Here is the output of these commands which clearly shows json_data valid – JSONField-in-serializers

Advanced concepts

Validations are part of Deserialization and not serialization. As explained earlier, serializing is process of converting already made data into another data type, so there is no requirement of these default validations out there. Deserialization requires validations as data needs to be saved to database or any more operation as specified. So if you serialize data using these fields that would work.

Core arguments in serializer fields

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Argument Description
read_only Set this to True to ensure that the field is used when serializing a representation, but is not used when creating or updating an instance during deserialization
write_only Set this to True to ensure that the field may be used when updating or creating an instance, but is not included when serializing the representation.
required Setting this to False also allows the object attribute or dictionary key to be omitted from output when serializing the instance.
default If set, this gives the default value that will be used for the field if no input value is supplied.
allow_null Normally an error will be raised if None is passed to a serializer field. Set this keyword argument to True if None should be considered a valid value.
source The name of the attribute that will be used to populate the field.
validators A list of validator functions which should be applied to the incoming field input, and which either raise a validation error or simply return.
error_messages A dictionary of error codes to error messages.
label A short text string that may be used as the name of the field in HTML form fields or other descriptive elements.
help_text A text string that may be used as a description of the field in HTML form fields or other descriptive elements.
initial A value that should be used for pre-populating the value of HTML form fields.

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