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YAML Parsers

The YamlParser class is used to parse YAML into POJOs.

The class hierarchy for the builder of this parser is:

Context.BuilderMarshallingContextable.BuilderParser.BuilderReaderParser.BuilderYamlParser.Builder

Refer to the builder javadocs for configurable settings.

The following pre-configured parsers are provided for convenience:

YamlParserDEFAULT

The YAML parser supports:

  • Block-style mappings and sequences (indentation-based).
  • Flow-style mappings ({key: value}) and sequences ([item1, item2]).
  • Plain, single-quoted, and double-quoted scalars.
  • Literal block scalars (|) and folded block scalars (>).
  • Comments (# ...).
  • Null values (null, ~).
  • Booleans (true, false).
  • Integer and floating-point numbers.
  • Document markers (---, ...).
  • Bean type dictionaries via _type property.

Usage​

// Parse YAML into a POJO
MyBean bean = YamlParser.DEFAULT.read(yaml, MyBean.class);

// Parse into generic types
JsonMap map = YamlParser.DEFAULT.read(yaml, JsonMap.class);
JsonList list = YamlParser.DEFAULT.read(yaml, JsonList.class);

// Parse with generic type parameters
List<MyBean> beans = YamlParser.DEFAULT.read(yaml, List.class, MyBean.class);

// Use the Yaml marshaller for convenience
MyBean bean = Yaml.to(yaml, MyBean.class);

Example​

public class Person {
    public int age;
    public String name;
    public List<String> tags;
}

String yaml = """
    # A person
    age: 5
    name: Zed
    tags: [a, b]
    """;

Person p = YamlParser.DEFAULT.read(yaml, Person.class);

Block and flow styles can be mixed freely, so tags: [a, b] and a - block sequence produce the same result.

Parser settings​

YamlParser has no format-specific builder settings. It inherits the standard settings from ReaderParser / Parser / MarshallingContext (for example trimStrings(), bean dictionaries, swaps and ignoreUnknownBeanProperties()). Media types consumed: application/yaml, text/yaml.

The @YamlConfig annotation (see YAML Serializers) only carries serializer-side settings today.

Limitations compared to JSON​

  • Maps with non-String keys (Boolean, Date, Temporal, Enum) may not round-trip when the target is a generic Map; LinkedHashMap / TreeMap with String keys work reliably.
  • There is no strict vs non-strict mode; YAML has no equivalent of JSON's lax parsing of unquoted attributes or concatenated strings.
  • Indentation is significant; malformed indentation can cause parse errors where equivalent JSON would parse.