These are the recommendation for rendering an instance of a nullable type without any other sample value provided.

null value

{ "type": [ "string", "null" ] }

(instance of a nullable string type)

xsi:nil="true" attribute

nil value

NULL value

None value

nil value

undef value

- key (string, optional)

The instance of key will be omitted in the rendered JSON:

{}

- key (string, optional, nullable)

The value of the instance will be unset in the rendered JSON:

{
  "key": null
}

- key (string, required)

The value of instance will be empty in the rendered JSON:

{
  "key": ""
}

- key (string, required, nullable)

The value of instance of key will be unset in the rendered JSON:

{
  "key": null
}