如何从架构中的json文件中获取缺少的字段，反之亦然

Question

I have installed jsonschema using pip install jsonschema .

from jsonschema import validate

schema_data = {
    "type" : "object",
    "properties" : {
        "price" : {"type" : "number"},
        "name" : {"type" : "string"},
        "additional" : {"type" : "number"},
        },
    }

json_data = {"name" : "Eggs", "price" : 34.99, "new": 90}

I am having above schema_data and json_data which is just validating the datatype.

Here additional is an extra field in schema_data which is absent in json_data , and new is present in json_data which is absent in schema_data .

How can I list missing fields like additional is missing in json_data and new is missing in schema_data ?

Answer 1

In a JSON Schema, by default properties are not required , all that your schema does is state what type they must be if the property is present . So for validation to flag that additional is missing, you need to mark that key as a required property first, by adding a required list with names:

schema_data = {
    "type" : "object",
    "properties" : {
        "price" : {"type" : "number"},
        "name" : {"type" : "string"},
        "additional" : {"type" : "number"},
        },
    "required": ["price", "name", "additional"]
}

Now validation will fail your JSON data because additional is missing:

>>> validate(json_data, schema_data)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/.../site-packages/jsonschema/validators.py", line 541, in validate
    cls(schema, *args, **kwargs).validate(instance)
  File "/.../site-packages/jsonschema/validators.py", line 130, in validate
    raise error
jsonschema.exceptions.ValidationError: 'additional' is a required property

Failed validating 'required' in schema:
    {'properties': {'additional': {'type': 'number'},
                    'name': {'type': 'string'},
                    'price': {'type': 'number'}},
     'required': ['price', 'name', 'additional'],
     'type': 'object'}

On instance:
    {'name': 'Eggs', 'new': 90, 'price': 34.99}

To make adding more keys invalid, you need to set additionalProperties to false ; the default is to allow for extra properties:

schema_data = {
    "type" : "object",
    "properties" : {
        "price" : {"type" : "number"},
        "name" : {"type" : "string"},
        "additional" : {"type" : "number"},
        },
    "required": ["price", "name", "additional"],
    "additionalProperties": False
}

However, with additional still missing, the addition of new key isn't found when you use validate() , because the first error found is raised as an exception.

To get all schema validation errors, create a validator object for the schema then use the IValidator.iter_errors() method to list all errors found:

from json_schema.validators import validator_for

validator = validator_for(schema_data)(schema_data)  # get class, create instance
for error in validator.iter_errors(json_data):
    print(error)

and now you get information about each error:

'additional' is a required property

Failed validating 'required' in schema:
    {'additionalProperties': False,
     'properties': {'additional': {'type': 'number'},
                    'name': {'type': 'string'},
                    'price': {'type': 'number'}},
     'required': ['price', 'name', 'additional'],
     'type': 'object'}

On instance:
    {'name': 'Eggs', 'new': 90, 'price': 34.99}
Additional properties are not allowed ('new' was unexpected)

Failed validating 'additionalProperties' in schema:
    {'additionalProperties': False,
     'properties': {'additional': {'type': 'number'},
                    'name': {'type': 'string'},
                    'price': {'type': 'number'}},
     'required': ['price', 'name', 'additional'],
     'type': 'object'}

On instance:
    {'name': 'Eggs', 'new': 90, 'price': 34.99}

Each error object in the loop is a ValidatorError exception object , which has a series of attributes can help you figure out exactly what the problem is, in code.