Jackson Integration

Jackson Integration

Use krandom-jackson when you want Jackson to understand kRandom schema definitions.

Jackson 2.x only

krandom-jackson is built for Jackson 2.x (com.fasterxml.jackson.core:jackson-databind, packages com.fasterxml.jackson.*) and brings jackson-databind 2.x transitively. KrandomJacksonModule extends Jackson 2’s SimpleModule; it cannot be registered with a Jackson 3 (tools.jackson.*) mapper. Spring Boot 4 defaults to Jackson 3, so its auto-configured JsonMapper does not pick the module up: use a Jackson 2 ObjectMapper, for example KrandomJackson.newObjectMapper(), for kRandom schema serialization. Jackson 2 and Jackson 3 use different packages and coexist on one classpath.

Dependency

Use Maven Central:

repositories {
    mavenCentral()
}

dependencies {
    implementation("io.github.frikit:krandom-core:2.10.0")
    implementation("io.github.frikit:krandom-jackson:2.10.0")
}

Configure An ObjectMapper

import com.fasterxml.jackson.databind.ObjectMapper;
import io.github.frikit.krandom.jackson.KrandomJackson;

ObjectMapper mapper = KrandomJackson.configure(new ObjectMapper());

KrandomJackson.newObjectMapper() is the shortest setup path:

ObjectMapper mapper = KrandomJackson.newObjectMapper();

Serialize A Schema As JSON Schema

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import io.github.frikit.krandom.generator.GeneratorConfig;
import io.github.frikit.krandom.generator.schema.Field;
import io.github.frikit.krandom.generator.schema.Schema;
import io.github.frikit.krandom.generator.schema.SchemaValueProvider;
import io.github.frikit.krandom.jackson.KrandomJackson;

import java.util.LinkedHashMap;
import java.util.Locale;
import java.util.Map;

GeneratorConfig cfg = GeneratorConfig.builder()
        .locale(Locale.US)
        .seed(42L)
        .build();

Field field = new Field(cfg);
Map<String, SchemaValueProvider> fields = new LinkedHashMap<>();
fields.put("order", field.bind("commerce.order_info"));
fields.put("company", field.bind("company.info"));
fields.put("payment", field.bind("finance.payment_info"));

Schema schema = new Schema(cfg, fields);
ObjectMapper mapper = KrandomJackson.newObjectMapper();

JsonNode jsonSchema = mapper.valueToTree(schema);
String type = jsonSchema.path("properties").path("order").path("type").asText(); // "object"

Serializing a Schema is side-effect free: it reads provider JSON Schema metadata and does not advance seeded row generation.

Serialize Generated Rows

Generated rows are ordinary Map<String, Object> values. Composite provider outputs are Java records, so Jackson serializes them as nested objects:

Map<String, Object> row = schema.generate();

JsonNode rowJson = mapper.valueToTree(row);
String orderNumber = rowJson.path("order").path("orderNumber").asText();
String companyName = rowJson.path("company").path("name").asText();

For non-Jackson exports, Schema also preserves composite records as structured data:

String jsonl = schema.toJsonLines(10);
String csv = schema.toCsv(10);
String xml = schema.toXml(10);
String sql = schema.toSqlInserts("public.orders", 10);
Map<String, Object> jsonSchemaMap = schema.toJsonSchema();