Java · Jackson JSON naming

Jackson snake_case ↔ camelCase

Keep Java properties idiomatic camelCase and translate snake_case external JSON names at the serialization boundary.

By Camel Case Converter Editorial TeamPublished Sep 12, 2026Last reviewed

Use @JsonNaming for one model or DTO

import com.fasterxml.jackson.databind.PropertyNamingStrategies;
import com.fasterxml.jackson.databind.annotation.JsonNaming;

@JsonNaming(PropertyNamingStrategies.SnakeCaseStrategy.class)
public class UserProfile {
  private String firstName;
  private String avatarUrl;
}

SnakeCaseStrategy maps properties such as firstName to first_name without annotating every field.

Use ObjectMapper for an application-wide convention

ObjectMapper mapper = new ObjectMapper();
mapper.setPropertyNamingStrategy(PropertyNamingStrategies.SNAKE_CASE);
UserProfile profile = mapper.readValue(json, UserProfile.class);
String output = mapper.writeValueAsString(profile);

PropertyNamingStrategies.SNAKE_CASE applies the external naming convention during serialization and deserialization.

Use @JsonProperty for explicit exceptions

public class UserProfile {
  @JsonProperty("user_id")
  private String userId;

  @JsonProperty("display_name")
  private String displayName;
}

Use @JsonProperty when only a few external names are unusual or should bypass the global rule.

Production considerations

  • Choose a clear ownership level: class-level strategy, application ObjectMapper, or explicit field mappings.
  • Naming strategies affect property names, not arbitrary string values in JSON.
  • Duplicate external names that normalize to one property are an API contract problem.
  • The examples use Jackson 2.x com.fasterxml.jackson packages; check your major-version migration notes.

Test the JSON boundary online

Use the browser tool to test nested objects, arrays, excluded keys, stop paths, semantic prefixes, collision handling, and a key-only diff before you copy the same convention into an application.

Drop a .json file here or choose one from your device

Files are read only in your browser. Maximum file size: 5 MB.

Converted JSON
{
  "user_profile": {
    "first_name": "Ada",
    "created_at": "2026-09-12"
  }
}

Parsing, file reading, formatting, and key conversion run locally in your browser. JSON input is not sent to a conversion server.

Related tools and guides

JSON → snake_caseJSON → camelCasesnake_case → camelCase in JavaAPI Case ConverterJSON Key Case ConverterPydantic camelCase ↔ snake_case