Custom vocabulary

This shows how to add support for custom keywords but only when your custom vocabulary is turned on.

EvaluatorFactory implementation

Implementation of CustomEvaluator is omitted for brevity.

import dev.harrel.jsonschema.Evaluator;
import dev.harrel.jsonschema.EvaluatorFactory;
import dev.harrel.jsonschema.JsonNode;
import dev.harrel.jsonschema.SchemaParsingContext;

import java.util.Optional;

class CustomEvaluatorFactory implements EvaluatorFactory {
    @Override
    public Optional<Evaluator> create(SchemaParsingContext ctx, String fieldName, JsonNode fieldNode) {
        if ("customKeyword".equals(fieldName) && ctx.getActiveVocabularies().contains("urn:custom-vocabulary")) {
            return Optional.of(new CustomEvaluator(ctx, fieldNode));
        }
        return Optional.empty();
    }
}

Dialect implementation

import dev.harrel.jsonschema.Dialects;
import dev.harrel.jsonschema.Draft2020EvaluatorFactory;
import dev.harrel.jsonschema.EvaluatorFactory;

import java.util.HashSet;
import java.util.Set;

class CustomDialect extends Dialects.Draft2020Dialect {
    @Override
    public String getMetaSchema() {
        return "urn:custom-dialect";
    }

    @Override
    public EvaluatorFactory getEvaluatorFactory() {
        return EvaluatorFactory.compose(new CustomEvaluatorFactory(), new Draft2020EvaluatorFactory());
    }

    @Override
    public Set<String> getSupportedVocabularies() {
        Set<String> supported = new HashSet<>(super.getSupportedVocabularies());
        supported.add("urn:custom-vocabulary");
        return supported;
    }
}

Meta-schema definition

{
  "$id": "urn:custom-dialect",
  "$ref": "https://json-schema.org/draft/2020-12/schema",
  "$vocabulary": {
    "https://json-schema.org/draft/2020-12/vocab/core": true,
    "https://json-schema.org/draft/2020-12/vocab/applicator": true,
    "https://json-schema.org/draft/2020-12/vocab/unevaluated": true,
    "https://json-schema.org/draft/2020-12/vocab/validation": true,
    "https://json-schema.org/draft/2020-12/vocab/meta-data": true,
    "https://json-schema.org/draft/2020-12/vocab/format-annotation": true,
    "https://json-schema.org/draft/2020-12/vocab/content": true,
    "urn:custom-vocabulary": true
  }
}

Example of schema definition

{
  "$id": "urn:schema",
  "$schema": "urn:custom-dialect",
  "customKeyword": "something"
}

Validator configuration

Validator validator = new ValidatorFactory()
    .withDialect(new CustomDialect())
    .createValidator();
validator.registerSchema(customMetaSchema);
validator.registerSchema(schema);

04 August 2025