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Serialize JSON object into a model object and retrieve a python dictionary on load
from django.db import models
from django.utils import simplejson as json
from django.conf import settings
from datetime import datetime
import time
class JSONEncoder(json.JSONEncoder):
def default(self, obj):
if isinstance(obj, datetime):
return obj.strftime('%Y-%m-%d %H:%M:%S')
elif isinstance(obj,
return obj.strftime('%Y-%m-%d')
elif isinstance(obj, datetime.time):
return obj.strftime('%H:%M:%S')
return json.JSONEncoder.default(self, obj)
class JSONDecoder(json.JSONDecoder):
def decode(self, json_string):
json_data = json.loads(json_string)
for key in json_data.keys():
json_data[key] = datetime.fromtimestamp(time.mktime(time.strptime(json_data[key], "%Y-%m-%d %H:%M:%S")))
except TypeError:
# It's not a datetime/time object
return json_data
class JSONField(models.TextField):
def _dumps(self, data):
return JSONEncoder().encode(data)
def _loads(self, str):
return JSONDecoder().decode(str)
def db_type(self):
return 'text'
def pre_save(self, model_instance, add):
value = getattr(model_instance, self.attname, None)
return self._dumps(value)
def contribute_to_class(self, cls, name):
self.class_name = cls
super(JSONField, self).contribute_to_class(cls, name)
def get_json(model_instance):
return self._dumps(getattr(model_instance, self.attname, None))
setattr(cls, 'get_%s_json' %, get_json)
def set_json(model_instance, json):
return setattr(model_instance, self.attname, self._loads(json))
setattr(cls, 'set_%s_json' %, set_json)
def post_init(self, **kwargs):
if 'sender' in kwargs and 'instance' in kwargs:
if kwargs['sender'] == self.class_name and hasattr(kwargs['instance'], self.attname):
value = self.value_from_object(kwargs['instance'])
if (value):
setattr(kwargs['instance'], self.attname, self._loads(value))
setattr(kwargs['instance'], self.attname, None)
class SampleModel(models.Model):
first_name = models.CharField(max_length=50)
last_name = models.CharField(max_length=50)
data = JSONField(null=True, blank=True)
data = {'pets': None, 'children': ['Benjamin', 'Clare', 'Joshua'], 'some_date': datetime(2010, 02, 01)}
# Test decode / encode
decode = JSONEncoder().encode(data)
encode = JSONDecoder().decode(decode)
# Save model
sample = SampleModel(first_name='Patrick', last_name='Altman') = data
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