Format Conversion

This example loads one supported format and saves another format through the core document model.

Converter

final class ConfigConverter {
  private final List<ConfigFormat> formats = List.of(
    YamlConfigFormat.INSTANCE,
    TomlConfigFormat.INSTANCE,
    JsonConfigFormat.INSTANCE,
    HoconConfigFormat.INSTANCE,
    PropertiesConfigFormat.INSTANCE
  );

  void convert(Path source, Path target) {
    var sourceLoader = loaderFor(source);
    var targetLoader = loaderFor(target);
    var document = ConfigLoaders.load(source, sourceLoader);
    ConfigLoaders.save(target, targetLoader, document);
  }

  private ConfigLoader loaderFor(Path path) {
    var extension = extension(path.getFileName().toString());
    return formats.stream()
      .filter(format -> format.extensions().contains(extension))
      .findFirst()
      .orElseThrow(() -> new ConfigException("Unsupported extension: " + extension))
      .loader();
  }

  private static String extension(String fileName) {
    var index = fileName.lastIndexOf('.');
    return index < 0 ? "" : fileName.substring(index + 1).toLowerCase(Locale.ROOT);
  }
}

Use It

new ConfigConverter().convert(
  Path.of("config.yml"),
  Path.of("config.toml")
);

What Carries Across

Core values, comments, ordering, and decorations stay available in memory. The target backend decides what can be written to the target file.

Source detail	Conversion behavior
Object and list values	Written when the target format supports the shape.
Scalar values	Written through the target backend’s scalar rules.
Leading comments	Written when the target backend supports comments.
YAML anchors or JSON5 radix	Kept as metadata, but not all target formats can render it.

Use conversion for import/export tools, not as a promise that every byte of source formatting will be identical in another format.