How to validate string and number using json schema

Question

I would like to validate a schema based on either its maximum/minimum (number) OR maximumLength/minimumLength (string). I have a json form:

[
  {
    "key":"foo",  
    "title":"Test",
    "type":"string" 
  }
]

and a json schema:

    {
 "type": "object",
  "properties": {
    "foo": {
        "type": ["number","string"],
        "maxLength":2,
        "minLength":0,
        "minimum":3,
        "maximum":10
    }
  }
}

and a json model:

{
  "foo": "bar"
}

Why does this example not work with validation? The model I have is not validated to false. According to this document it is possible to have different types defined in an array, but how can we do validation based on min/max values?

Jason Desrosiers · Accepted Answer · 2016-01-27 19:49:18Z

2

Your schema is correct. The validator you are using doesn't work properly. Here is an alternative that uses anyOf instead.

{
    "type": "object",
    "properties": {
        "foo": {
            "anyOf": [
                { "$ref": "#/definitions/boundedNumber" }
                { "$ref": "#/definitions/boundedString" }
            ]
        }
    },
    "definitions": {
        "boundedString": {
            "type": "string",
            "maxLength": 2,
            "minLength": 0
        },
        "boundedNumber": {
            "type": "number",
            "minimum": 3,
            "maximum": 10
        }
    }
}

Although it is quite a bit longer, some would argue that this is actually easier to read/maintain because of the separation of the type specific keywords.

answered Jan 27, 2016 at 19:49

Jason Desrosiers

24.8k7 gold badges54 silver badges61 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

John Over a year ago

Your suggestion works with the json schema, but it still will not work with the library I am using: angular-schema-form validation, which is also using json schema. I think maybe there is something wrong withe the library.

Jason Desrosiers Over a year ago

I played around with the angular-schema-form validation demo page and it looks like it supports only the most basic JSON Schema features. What it does support isn't even entirely compliant with the JSON Schema spec.

Anthropic Over a year ago

Nor should it be, UI is far more complex than JSON Schema can currently handle and as the goal is to work within the UI, many JSON Schema rules are quite problematic, which is why there is a proposal to add a UI vocabulary to JSON Schema to reduce confusion and make it easy to work with for UI generation.

jruizaranguren · Accepted Answer · 2016-01-27 12:20:01Z

2

Your schema is validating JSON objects ("type":"object"). In addition, if they have a property with key "foo", its value must be either a number between 3 an 10, or a string of maximum length 2.

Valid objects according to your schema:

{"foo":6}
{"foo":"as"}

Invalid objects:

{"foo":60}
{"foo":"asereje"}

If you want to validate arrays you must define your parent object as an array and use items tag to specify the schema for the array items, for instance:

{
    "type" : "array",
    "items" : {
        "type" : "object",
        "properties" : {
            "foo" : {
                "type" : ["number", "string"],
                "maxLength" : 2,
                "minLength" : 0,
                "minimum" : 3,
                "maximum" : 10
            }
        }
    }
}

The schema above would validate the following JSON array:

[{
        "foo" : 6
    }, {
        "foo" : "as"
    }
]

answered Jan 27, 2016 at 12:20

jruizaranguren

13.8k7 gold badges60 silver badges74 bronze badges

3 Comments

John Over a year ago

I edited my question to add a model, to avoid confusion with the form. I am not able to get the example you provided to work as intended. Do I have to change my form as well?

jruizaranguren Over a year ago

You can test that the example validates the provided JSON here: json-schema-validator.herokuapp.com

John Over a year ago

You are completely right. I think maybe it is something wrong with the angular-schema-form validation.

Anthropic · Accepted Answer · 2017-07-21 01:51:01Z

John the issue is the type "type" : ["number", "string"]

Angular Schema Form is generating fields from the combined JSON Schema and the UI Schema (form), when the field type is defined it knows which type to validate against, when there are multiple types it doesn't know which part of the spec to base the form field against, so it falls back to a textbox and does not add the appropriate validation requirements for string alone.

To achieve your desired outcome you would need to tell it which field type you wish to use. There is a bug in the 0.8.x versions where it does not validate based on the type set in the UI schema if it cannot determine the type in the data schema, I believe that is fixed in the latest development branch. If not if there is an issue raised in Git, I would prioritise it.

Collectives™ on Stack Overflow

How to validate string and number using json schema

3 Answers 3

3 Comments

3 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

3 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related