Example 1: Primitive and complex types with null values

In OpenAPI 3.0, null values for both primitive and complex data types are represented using the nullable: true property.

To accept null values in Genero BDL, you must configure your variables in one of the following ways:

• Define the variable with the json_null="null" attribute so it accepts NULL in addition to its base type (for example, STRING)
• Enable null handling globally by setting the allowNullAsDefault option in the The json.Serializer class

If null values are not handled using one of these approaches, serialization error-15807 is raised.

When working with user-defined record types, a special case applies. If a record is defined with json_null="null", its fields can also contain null values. The following example shows a tAddress record type with nullable fields:

TYPE tAddress RECORD
    street STRING,
    city STRING,
    state STRING,
    zip STRING
END RECORD

TYPE customer RECORD
    lastname STRING ATTRIBUTES(json_null="null"),
    firstname STRING,
    address tAddress ATTRIBUTE(json_null="null")
END RECORD

In this example, fglrestful maps the Genero BDL types to the JSON object schema as follows:

• The nullable: true property is set for fields that accept null values.
• The anyOf property is used to allow fields to accept either the expected type or NULL.
• The tAddress type is defined as a reference ($ref) in the components/schemas section, where its schema is declared.

When a property uses a $ref, OpenAPI requires it to be wrapped in an anyOf clause if it appears alongside the nullable property. The following example shows how this is represented in the generated OpenAPI document:

 "content": {
	"application/json": {
	    "schema": {
		  "type": "object",
		   "properties": {
			 "lastname": {
			     "type": "string",
			     "nullable": true
			 },
			 "firstname": {
			     "type": "string"
			 },
			 "address": {
			     "nullable": true,
			     "anyOf": [
			        {
			         "$ref": "#/components/schemas/tAddress"
			        }
			     ]
		         },