Add null to enum definition

[enthimema]

Hello I am trying to validate a json based on a schema generated from the class below and I was wondering if there is a way to add null to the enum definition during the generation without modifying the enum definition? I tried to use @null on field, but has no impact on enum definition. Thanks in advance for you support.

Class and enums definitions

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class UiField {
...
     @Null
     private UiFieldDisplayType displayType;
     @Null
     private UiFieldContentType contentType;
...
}

public enum UiFieldDisplayType {
    fieldNameAndAddress,
    fieldName,
    fieldAddress;
}

public enum UiFieldContentType {
  combobox, checkbox, text;
}

Generated schema

"contentType": {
	"type": [
		"string",
		"null"
	],
	"enum": [
		"combobox",
		"checkbox",
		"text",
                null <- add this during generation
	] 
},

"displayType": {
	"type": [
		"string",
		"null"
	],
	"enum": [
		"fieldNameAndAddress",
		"fieldName",
		"fieldAddress",
                 null          <- add this during generation
	]
}

Input JSON for validate

{
...
"displayType": null,
"contentType": "combobox",
...
}

[CarstenWickner]

HI @enthimema,

In what way is the enum generated?
Are you using one of the standard options or some kind of custom definition?
I was expecting the nullable definition to look more like this:

{
    "anyOf": [
        {
            "type": "null"
        },
        {
            "type": "string",
            "enum": [
                "fieldNameAndAddress",
                "fieldName",
                "fieldAddress"
            ]
        }
    ]
}

Perhaps the automatic clean-up logic is not correct there.

[enthimema]

Hi @CarstenWickner ,

Thanks for your reply. This is how I'm doing it

JakartaValidationModule module = new JakartaValidationModule(JakartaValidationOption.INCLUDE_PATTERN_EXPRESSIONS);
SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_7, OptionPreset.PLAIN_JSON)
                .with(Option.FORBIDDEN_ADDITIONAL_PROPERTIES_BY_DEFAULT)
                .with(module);

SchemaGeneratorConfig config = configBuilder.build();
SchemaGenerator generator = new SchemaGenerator(config);
JsonNode jsonSchema = generator.generateSchema(UiField.class);
System.out.println(jsonSchema);

I also tried adding .with(Option.NULLABLE_FIELDS_BY_DEFAULT ) to the config Builder

[CarstenWickner]

I'll have a look over the weekend and get back to you.
Might need a bug fix there.

[enthimema]

Hi @CarstenWickner , I'm posting here a full example. I removed the Option.FORBIDDEN_ADDITIONAL_PROPERTIES_BY_DEFAULT , but I don't think it matters.

UiField.java

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class UiField {
    private String name;
    private boolean mandatory;
    private UiSubField subfield;
    @Null
    private UiFieldDisplayType displayType;
    @Null
    private UiFieldContentType contentType;
}

UiSubField.java

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class UiSubField {
    private String subField;
    private boolean enabled;
}

UiFieldContentType.java

public enum UiFieldContentType {
    combobox, checkbox, text;
}

UiFieldDisplayType.java

public enum UiFieldDisplayType {
    fieldNameAndAddress, fieldName, fieldAddress;
}

JsonSchema.json

{
	"$schema": "http://json-schema.org/draft-07/schema#",
	"type": "object",
	"properties": {
		"contentType": {
			"type": [
				"string",
				"null"
			],
			"enum": [
				"combobox",
				"checkbox",
				"text"
			]
		},
		"displayType": {
			"type": [
				"string",
				"null"
			],
			"enum": [
				"fieldNameAndAddress",
				"fieldName",
				"fieldAddress"
			]
		},
		"mandatory": {
			"type": "boolean"
		},
		"name": {
			"type": "string"
		},
		"subfield": {
			"type": "object",
			"properties": {
				"enabled": {
					"type": "boolean"
				},
				"subField": {
					"type": "string"
				}
			}
		}
	}
}

inputJson.json

{
	"name": "FieldName",
	"mandatory": true,
	"subfield": {
		"subField": null,
		"enabled": false
	},
	"displayType": null,
	"contentType": "text"
}

validation Message

[
$.displayType: does not have a value in the enumeration [fieldNameAndAddress, fieldName, fieldAddress],
$.subfield.subField: null found, string expected
]

For the $.subfield.subField I understand why the message appears as it doesn't have @Null annotation
But the $.displayType, on the other hand, has it.

This is how I generate the schema and validate the json.

JakartaValidationModule module = new JakartaValidationModule(JakartaValidationOption.INCLUDE_PATTERN_EXPRESSIONS);
SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_7, OptionPreset.PLAIN_JSON)
                .with(module);
SchemaGeneratorConfig config = configBuilder.build();
SchemaGenerator generator = new SchemaGenerator(config);
JsonNode jsonSchema = generator.generateSchema(UiField.class);
System.out.println(jsonSchema);

ObjectMapper mapper = new ObjectMapper();

JsonNode node = mapper.readTree(jsonSchema.toPrettyString());
JsonSchemaFactory factory = JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V7);
JsonSchema schema = factory.getSchema(node);

String inputJson = mapper.writeValueAsString(UiField.builder().name("FieldName").contentType(UiFieldContentType.text).mandatory(true).subfield(UiSubField.builder().build()).build());
System.out.println(inputJson);
JsonNode curValue = mapper.readTree(inputJson);
Set<ValidationMessage> errors = schema.validate(curValue);
System.out.println(errors);

Do you think the schema is invalid or not right for the enums? Thank you.

[CarstenWickner]

Hello again @enthimema,

First of all, as already hinted at above (and described explicitly on #213), the handling of null values on enum types had a bug.
A bug fix was created and just released in v4.21.0.
Therefore, please update the jsonschema-generator dependencies accordingly.

Secondly, your configuration is not quite right yet.

1. The @Null annotation (according to its JavaDoc) is supposed to be used for fields that are always null. It is therefore the incorrect choice (even though the resulting schema is not reflecting that interpretation, but I didn't bother "fixing" that now as well. There is a @javax.validation.Nullable annotation, which Is probably what you had in mind, but that's not supported out-of-the-box today.
2. Instead, as you already mentioned yourself, you should rather use the Option.NULLABLE_FIELDS_BY_DEFAULT and then annotate the mandatory fields with @NotNull.
3. As per the second error message you were getting, the "subField" property should also be treated as nullable if you want to be able to send null.

---

I've adjusted your given example to make it work (now against the new library version 4.21.0):

Type Definitions

public class UiField {
    @NotNull
    public String name;
    @NotNull
    public boolean mandatory;
    @NotNull
    public UiSubField subfield;
    public UiFieldDisplayType displayType;
    public UiFieldContentType contentType;
}

public class UiSubField {
    public String subField;
    @NotNull
    public boolean enabled;
}

public enum UiFieldContentType {
    combobox, checkbox, text;
}

public enum UiFieldDisplayType {
    fieldNameAndAddress, fieldName, fieldAddress;
}

Test Code

JakartaValidationModule module = new JakartaValidationModule(JakartaValidationOption.INCLUDE_PATTERN_EXPRESSIONS);
SchemaGeneratorConfigBuilder configBuilder = new SchemaGeneratorConfigBuilder(SchemaVersion.DRAFT_7, OptionPreset.PLAIN_JSON)
        .with(Option.NULLABLE_FIELDS_BY_DEFAULT)
        .with(module);
SchemaGeneratorConfig config = configBuilder.build();
SchemaGenerator generator = new SchemaGenerator(config);
JsonNode jsonSchema = generator.generateSchema(UiField.class);
System.out.println(jsonSchema.toPrettyString() + "\n————————————————————");

ObjectMapper mapper = new ObjectMapper();

JsonNode curValue = mapper.readTree("{\n"
        + "	\"name\": \"FieldName\",\n"
        + "	\"mandatory\": true,\n"
        + "	\"subfield\": {\n"
        + "		\"subField\": null,\n"
        + "		\"enabled\": false\n"
        + "	},\n"
        + "	\"displayType\": null,\n"
        + "	\"contentType\": \"text\"\n"
        + "}");
JsonSchemaFactory factory = JsonSchemaFactory.getInstance(SpecVersion.VersionFlag.V7);
JsonSchema schema = factory.getSchema(jsonSchema);
Set<ValidationMessage> errors = schema.validate(curValue);
System.out.println(errors);

Generated Schema

{
  "$schema" : "http://json-schema.org/draft-07/schema#",
  "type" : "object",
  "properties" : {
    "contentType" : {
      "anyOf" : [ {
        "type" : "null"
      }, {
        "type" : "string",
        "enum" : [ "combobox", "checkbox", "text" ]
      } ]
    },
    "displayType" : {
      "anyOf" : [ {
        "type" : "null"
      }, {
        "type" : "string",
        "enum" : [ "fieldNameAndAddress", "fieldName", "fieldAddress" ]
      } ]
    },
    "mandatory" : {
      "type" : "boolean"
    },
    "name" : {
      "type" : "string"
    },
    "subfield" : {
      "type" : "object",
      "properties" : {
        "enabled" : {
          "type" : "boolean"
        },
        "subField" : {
          "type" : [ "string", "null" ]
        }
      }
    }
  }
}

[enthimema]

Hi @CarstenWickner , wow, thanks for the quick fix and for your support. And also for the tips regarding the @Null . At the moment I cannot check but will do and come with feedback. Thanks again, really appreciate your work.

[enthimema]

Hi @CarstenWickner , I can confirm it works as you mentioned. I had some issues with Maven recognizing the proper version, but now it's fine. Thank you and have a nice day!