我有一个带有JSONField (django.contrib.postgres.fields.JSONField) 的 django 模型
有什么方法可以根据 json 模式文件验证模型数据吗？
（预保存）
类似my_field = JSONField(schema_file=my_schema_file)
【问题讨论】：
标签： json django postgresql jsonschema
为了做到这一点，我使用jsonschema 编写了一个自定义验证器。
project/validators.py
import django
from django.core.validators import BaseValidator
import jsonschema
class JSONSchemaValidator(BaseValidator):
def compare(self, value, schema):
try:
jsonschema.validate(value, schema)
except jsonschema.exceptions.ValidationError:
raise django.core.exceptions.ValidationError(
'%(value)s failed JSON schema check', params={'value': value}
)
project/app/models.py
from django.db import models
from project.validators import JSONSchemaValidator
MY_JSON_FIELD_SCHEMA = {
'schema': 'http://json-schema.org/draft-07/schema#',
'type': 'object',
'properties': {
'my_key': {
'type': 'string'
}
},
'required': ['my_key']
}
class MyModel(models.Model):
my_json_field = models.JSONField(
default=dict,
validators=[JSONSchemaValidator(limit_value=MY_JSON_FIELD_SCHEMA)]
)
【讨论】：
这就是 Model.clean() 方法的用途 (see docs)。示例：
class MyData(models.Model):
some_json = JSONField()
...
def clean(self):
if not is_my_schema(self.some_json):
raise ValidationError('Invalid schema.')
【讨论】：
您可以使用cerberus 根据架构验证您的数据
from cerberus import Validator
schema = {'name': {'type': 'string'}}
v = Validator(schema)
data = {'name': 'john doe'}
v.validate(data) # returns "True" (if passed)
v.errors # this would return the error dict (or on empty dict in case of no errors)
使用起来非常简单（也因为它的文档很好 -> 验证规则：http://docs.python-cerberus.org/en/stable/validation-rules.html）
【讨论】：
我编写了一个自定义的JSONField，它扩展了models.JSONField，并使用jsonschema（Django 3.1、Python 3.7）验证了属性的值。
我没有使用validators参数有一个原因：我想让用户动态定义架构。所以我使用schema参数，应该是：
None（默认）：该字段的行为与其父类相似（不支持 JSON 模式验证）。dict 对象。此选项适用于小型架构定义（例如：{"type": "string"}）；str 对象，描述了包含架构代码的文件的路径。此选项适用于大模式定义（以保留模型类定义代码的美感）。对于搜索，我使用所有启用的查找器：django.contrib.staticfiles.finders.find()。dict 对象返回的函数。因此，您可以根据给定模型实例的状态构建模式。每次调用validate()时都会调用该函数。myapp/models/fields.py
import json
from jsonschema import validators as json_validators
from jsonschema import exceptions as json_exceptions
from django.contrib.staticfiles import finders
from django.core import checks, exceptions
from django.db import models
from django.utils.functional import cached_property
class SchemaMode:
STATIC = 'static'
DYNAMIC = 'dynamic'
class JSONField(models.JSONField):
"""
A models.JSONField subclass that supports the JSON schema validation.
"""
def __init__(self, *args, schema=None, **kwargs):
if schema is not None:
if not(isinstance(schema, (bool, dict, str)) or callable(schema)):
raise ValueError('The "schema" parameter must be bool, dict, str, or callable object.')
self.validate = self._validate
else:
self.__dict__['schema_mode'] = False
self.schema = schema
super().__init__(*args, **kwargs)
def check(self, **kwargs):
errors = super().check(**kwargs)
if self.schema_mode == SchemaMode.STATIC:
errors.extend(self._check_static_schema(**kwargs))
return errors
def _check_static_schema(self, **kwargs):
try:
schema = self.get_schema()
except (TypeError, OSError):
return [
checks.Error(
f"The file '{self.schema}' cannot be found.",
hint="Make sure that 'STATICFILES_DIRS' and 'STATICFILES_FINDERS' settings "
"are configured correctly.",
obj=self,
id='myapp.E001',
)
]
except json.JSONDecodeError:
return [
checks.Error(
f"The file '{self.schema}' contains an invalid JSON data.",
obj=self,
id='myapp.E002'
)
]
validator_cls = json_validators.validator_for(schema)
try:
validator_cls.check_schema(schema)
except json_exceptions.SchemaError:
return [
checks.Error(
f"{schema} must be a valid JSON Schema.",
obj=self,
id='myapp.E003'
)
]
else:
return []
def deconstruct(self):
name, path, args, kwargs = super().deconstruct()
if self.schema is not None:
kwargs['schema'] = self.schema
return name, path, args, kwargs
@cached_property
def schema_mode(self):
if callable(self.schema):
return SchemaMode.DYNAMIC
return SchemaMode.STATIC
@cached_property
def _get_schema(self):
if callable(self.schema):
return self.schema
elif isinstance(self.schema, str):
with open(finders.find(self.schema)) as fp:
schema = json.load(fp)
else:
schema = self.schema
return lambda obj: schema
def get_schema(self, obj=None):
"""
Return schema data for this field.
"""
return self._get_schema(obj)
def _validate(self, value, model_instance):
super(models.JSONField, self).validate(value, model_instance)
schema = self.get_schema(model_instance)
try:
json_validators.validate(value, schema)
except json_exceptions.ValidationError as e:
raise exceptions.ValidationError(e.message, code='invalid')
用法：
myapp/models/__init__.py
def schema(instance):
schema = {}
# Here is your code that uses the other
# instance's fields to create a schema.
return schema
class JSONSchemaModel(models.Model):
dynamic = JSONField(schema=schema, default=dict)
from_dict = JSONField(schema={'type': 'object'}, default=dict)
# A static file: myapp/static/myapp/schema.json
from_file = JSONField(schema='myapp/schema.json', default=dict)
【讨论】：
另一种使用jsonschema 处理简单情况的解决方案。
class JSONValidatedField(models.JSONField):
def __init__(self, *args, **kwargs):
self.props = kwargs.pop('props')
self.required_props = kwargs.pop('required_props', [])
super().__init__(*args, **kwargs)
def validate(self, value, model_instance):
try:
jsonschema.validate(
value, {
'schema': 'http://json-schema.org/draft-07/schema#',
'type': 'object',
'properties': self.props,
'required': self.required_props
}
)
except jsonschema.exceptions.ValidationError:
raise ValidationError(
f'Value "{value}" failed schema validation.')
class SomeModel(models.Model):
my_json_field = JSONValidatedField(
props={
'foo': {'type': 'string'},
'bar': {'type': 'integer'}
},
required_props=['foo'])
【讨论】：