Type Attribute Overrides

[dalucasPeraton]

I am trying to get the type attribute overrides to work and it mentions the use of the annotation
@ValidOneOfTypes

Where is that annotation implemented? The use of an object type with overrides using the annotation is very powerful but I am unable to track down the import to use it.

https://victools.github.io/jsonschema-generator/#type-attribute-overrides

Thanks for any help in advance.

[CarstenWickner]

Hi @dalucasPeraton,

There was no particular annotation of that name. It is merely a fictional example to illustrate the use of those Type Attribute Overrides.
You can create the annotation type yourself if you want to use it for such a scenario.

@Retention(RetentionPolicy.RUNTIME)
@interface ValidOneOfTypes {
  Class[] value();
}

EDIT: as discussed below, the @Retention(RetentionPolicy.RUNTIME) is required for the annotation being picked up by the schema generator at runtime. Other annotations are (currently) not considered.

Alternatively, you could use the jsonschema-module-swagger-2 and add the @Schema(anyOf = {String.class, Number.class}) annotation. That would be the io.swagger.v3.oas.annotations.media.Schema annotation to be exact.
The Swagger 2 module uses a Sub Type Resolver internally instead of a Type Attribute Override, but the result is the same.

[dalucasPeraton]

I have tried both methods and only receive an empty object property without the anyOf reference aka "value": { }

I created a java objects:

public @interface ValidOneOfTypes {
    Class[] value();    
}

@Data
@NoArgsConstructor
@AllArgsConstructor
@JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class)
public class Observation {
    
    @JsonProperty(required = true)
    private String observationType;
    @ValidOneOfTypes({String.class, Number.class, Boolean.class})
    private Object value;
    private String unitOfMeasure;
    

    public void setValue(String textValue) {
        this.value = textValue;
    }
    public void setValue(Number numericValue) {
        this.value = numericValue;
    }
    public void setValue(Boolean booleanValue) {
        this.value = booleanValue;
    }

}

public class ObservationSchemaGenerator {
    public static void main(String[] args) {

        JavaxValidationModule javaxModule = new JavaxValidationModule(
                JavaxValidationOption.NOT_NULLABLE_FIELD_IS_REQUIRED);
        JacksonModule jacksonModule = new JacksonModule(JacksonOption.RESPECT_JSONPROPERTY_REQUIRED,
                JacksonOption.RESPECT_JSONPROPERTY_ORDER);

        SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_2020_12,
                OptionPreset.PLAIN_JSON)
                        .with(Option.EXTRA_OPEN_API_FORMAT_VALUES, Option.FLATTENED_ENUMS_FROM_TOSTRING,
                                Option.DEFINITIONS_FOR_ALL_OBJECTS)
                        .with(javaxModule).with(jacksonModule);
        configBuilder.forFields()
                .withTargetTypeOverridesResolver(field -> Optional
                        .ofNullable(field.getAnnotationConsideringFieldAndGetterIfSupported(ValidOneOfTypes.class))
                        .map(ValidOneOfTypes::value).map(Stream::of)
                        .map(stream -> stream.map(specificSubtype -> field.getContext().resolve(specificSubtype)))
                        .map(stream -> stream.collect(Collectors.toList()))
                        .orElse(null));
        SchemaGeneratorConfig config = configBuilder.build();
        SchemaGenerator generator = new SchemaGenerator(config);
        JsonNode jsonSchema = generator.generateSchema(Observation.class);

        System.out.println(jsonSchema.toPrettyString());

    }
}

{
  "$schema" : "https://json-schema.org/draft/2020-12/schema",
  "type" : "object",
  "properties" : {
    "observation_type" : {
      "type" : "string"
    },
    "unit_of_measure" : {
      "type" : "string"
    },
    "value" : { }
  },
  "required" : [ "observation_type" ]
}

[CarstenWickner]

Thanks for the complete example. You only need to add @Retention(RetentionPolicy.RUNTIME) on your annotation definition, in order for it to become visible at the time of the schema generation.
Then it works as expected:

@Retention(RetentionPolicy.RUNTIME)
@interface ValidOneOfTypes {
    Class[] value();
}

Then the result looks like this:

{
  "$schema" : "https://json-schema.org/draft/2020-12/schema",
  "type" : "object",
  "properties" : {
    "observation_type" : {
      "type" : "string"
    },
    "value" : {
      "anyOf" : [ {
        "type" : "string"
      }, {
        "type" : "number"
      }, {
        "type" : "boolean"
      } ]
    }
  },
  "required" : [ "observation_type" ]
}

I'm updating my original answer now accordingly.

[dalucasPeraton]

I used Jackson annotations:

@JsonSubTypes(
        {
            @JsonSubTypes.Type(value = String.class),
            @JsonSubTypes.Type(value = Number.class),
            @JsonSubTypes.Type(value = ZonedDateTime.class),
            @JsonSubTypes.Type(value = Boolean.class)
        }
    )
    @JsonPropertyDescription("The observation can be string, numerical, or a boolean value")
    @JsonProperty(required = true)
    private Object value;

This worked as I expected.