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jsonvalidationgooption-type

JSON schema validation of optional fields using Golang

Golang JSON schema validation libraries validate that required fields on the schema are present in the service request/response.

I need to validate that any field in a service request or response must be a property on the schema. If a property in the payload does not exist in the schema, the validation should fail.

For example: a GET response:

{
   "pet": "dog",
   "name": "Scooby",
   "licence": "123-123"
}

In my sample JSON schema, none of the fields are required. However, if I changed the field "pet" to "petBreed" in my service, it will not be caught by a JSON schema validator (e.g. https://github.com/xeipuuv/gojsonschema).

Making all fields required is not an option. Can anyone suggest a library in Go that will:

  1. validate that all the response fields are in the schema
  2. not fail if a field from the schema isn't in the response
Solution

  • JSON Schema defines additionalProperties for this purpose, something like this schema should work:

    {
    "type": "object",
    "additionalProperties": false,
    "properties":{
        "pet": ...,
        "name": ...,
        "license": ...,
    },
}

    This is implemented but not documented as such in gojsonschema.

    Note that additionalProperties is a schema, not just a boolean, i.e. you can do arbitrary validation of unknown properties, not just disallow them.