json library

JSON for Dart objects: ObjectMapper turns objects into JSON and back, without hand-written fromJson / toJson methods.

Import it to read and write JSON in your own code, to shape the JSON of a model with Jackson-style annotations (@JsonProperty, @JsonIgnore, @JsonInclude, @JsonFormat, @JsonTypeInfo, ...), or to add a serializer for a type the mapper does not know. It is also exported by package:spring_core_dart/spring_core_dart.dart. The web and Feign starters use the same mapper for request and response bodies, so these annotations shape the HTTP JSON too. The mapper reads metadata that spring_core_dart_generator writes for classes marked @Introspected(); there is no reflection. It also offers a tree model (JsonNode), naming strategies and JsonMapper.builder().

@Introspected()
class Book {
  const Book({required this.isbn, required this.title});
  final String isbn;
  final String title;
}

// In Spring Boot the mapper is a bean: inject ObjectMapper.
final json = mapper.writeValueAsString(
  const Book(isbn: '1', title: 'Dune'),
);
final book = mapper.readValue<Book>(json);

Spring (Java): Jackson's com.fasterxml.jackson.databind, configured by Spring Boot's JacksonAutoConfiguration.

Classes

ArrayNode: A JSON array: an ordered list of child nodes, which can be changed in place.
BooleanNode: A JSON true or false.
ClassType<T>: The TypeInfo of a class or scalar type that needs no further description: ClassType<String>(), ClassType<Book>().
DynamicType: The TypeInfo of dynamic, Object? or a type that is not described further: values are taken as they are. void (e.g. of ResponseEntity<void>) is DynamicType.forVoid, so a reader can ignore the value.
EnumType<E extends Enum>: The TypeInfo of an enum, with its values, so a value can be found by name: EnumType<Mood>(Mood.values). jsonValue reads the field marked @JsonValue(), when the enum has one.
GenericType<T>: The TypeInfo of a generic class other than the collections, with the descriptions of its type arguments: GenericType<ResponseEntity<Book>>([ClassType<Book>()]). T is the whole type; arguments describe its type arguments in order.
JsonAlias: Other JSON names a property (or constructor parameter) is read from, besides its own.
JsonAnyGetter: Writes the entries of a map property as extra properties of the object, after the declared ones.
JsonAnySetter: Collects the JSON properties a class does not have, instead of skipping them or failing.
JsonCreator: Marks the constructor (or factory constructor) the mapper creates objects with when reading JSON.
JsonDeserializer<T extends Object>: Custom code that builds values of T from decoded JSON, for a type the mapper cannot read on its own or should read differently.
JsonFeature: An on/off setting of a mapper, named after Jackson's feature flags.
JsonFormat: Changes the JSON form of one property's value: a date pattern and time zone, or a shape (a number as a string, an enum by index, ...).
JsonIgnore: Leaves a property out of JSON in both directions.
JsonIgnoreProperties: Lists JSON properties a class ignores, and can make it accept unknown ones when reading.
JsonInclude: Decides which values of a property, or of every property of a class, are written: for example, leave out nulls.
JsonMapper: An ObjectMapper with a builder, for configuring a mapper step by step in Jackson 3's style.
JsonMapperBuilder: Collects settings, serializers and modules, then creates a JsonMapper with build.
JsonModule: A group of serializers and deserializers that is added to a mapper in one step.
JsonNaming: Sets the naming strategy of one class's properties, overriding the mapper's.
JsonNode: One value of a JSON document held as a tree: an object, array, string, number, boolean or null, with typed accessors for navigating it.
JsonProperty: Gives a property, constructor parameter or enum constant another name in JSON, or limits it to one direction.
JsonPropertyOrder: Puts chosen properties of a class first when it is written, for JSON that people read or that a fixed format expects.
JsonSerializer<T extends Object>: Custom code that writes values of T as JSON, for a type the mapper cannot handle or should write differently.
JsonSubType: One entry of JsonSubTypes: a subclass and the type ids it is written and read with (Jackson's @JsonSubTypes.Type).
JsonSubTypes: Lists the subclasses of a @JsonTypeInfo class and their type ids.
JsonTypeInfo: Makes a class hierarchy polymorphic in JSON: each object carries a type id, so a value of the base type is read back as the right subclass.
JsonTypeName: Sets the type id of a subclass in a @JsonTypeInfo hierarchy.
JsonUnwrapped: Writes the properties of a nested object inline, in the enclosing object, instead of under its own key.
JsonValue: Makes one value stand for the whole object in JSON: an enum constant's JSON form, or a small value class written as a plain string or number.
JsonView: Puts a property into one or more views, so the same class can be written with fewer or more properties depending on who reads it.
ListType<E>: The TypeInfo of a List<E>, with the description of its elements: ListType<Book>(ClassType<Book>()).
MapType<K, V>: The TypeInfo of a Map<K, V>, with the descriptions of its keys and values: MapType<String, int>(ClassType<String>(), ClassType<int>()).
MissingNode: The stand-in that JsonNode.path and JsonNode.at return where the document has no node, so navigation can go on without null checks.
NullNode: A JSON null value, which is present (unlike a MissingNode).
NumericNode: A JSON number: an int when the JSON had no fraction, else a double.
ObjectMapper: Converts Dart objects to JSON and back: the one place where models, JSON text, decoded maps and JsonNode trees meet.
ObjectNode: A JSON object: named child nodes, kept in insertion order.
ObjectReader: A reader bound to one @JsonView: it reads only the properties of that view and skips the others, with its mapper's settings.
ObjectWriter: A writer bound to one @JsonView: it writes only the properties of that view, with its mapper's settings.
SetType<E>: The TypeInfo of a Set<E>, with the description of its elements: SetType<String>(ClassType<String>()).
StringNode: A JSON string. asInt, asDouble and asBoolean convert numeric and "true" / "false" text.
TypeInfo<T>: A description of a full Dart type, such as List<Book> or String?, that code can take apart at run time without reflection.
TypeInfoVisitor<R>: One method per kind of TypeInfo, called by TypeInfo.accept with the kind's type arguments in scope.

Enums

DateTimeFeature: On/off settings for writing and reading DateTime and Duration, named after Jackson 3's DateTimeFeature (set by spring.json.datatype.datetime.*; Spring Boot 4: spring.jackson.datatype.datetime.*).
DeserializationFeature: On/off settings for reading JSON, named after Jackson's DeserializationFeature; the defaults are Spring Boot's.
JsonFormatShape: The JSON shapes JsonFormat.shape can ask for (Jackson's JsonFormat.Shape).
JsonInclusion: Which property values are written, for JsonInclude and the mapper's inclusion (Jackson's JsonInclude.Include).
JsonPropertyAccess: The directions a property takes part in, for JsonProperty.access (Jackson's JsonProperty.Access).
JsonTypeId: What identifies the subclass in JSON, for JsonTypeInfo.use (Jackson's JsonTypeInfo.Id).
JsonTypeInclusion: Where the type id is placed, for JsonTypeInfo.include (Jackson's JsonTypeInfo.As).
MapperFeature: On/off settings that change how the mapper sees classes, named after Jackson's MapperFeature.
PropertyNamingStrategy: A rule that turns Dart property names (publishedAt) into JSON names (published_at), applied to every property of a class or of the whole mapper.
SerializationFeature: On/off settings for writing JSON, named after Jackson's SerializationFeature.

Exceptions / Errors

JsonMappingException: The error the JSON mapper throws when JSON cannot be turned into the requested type, or a value cannot be written as JSON.
JsonNodeException: The error a JsonNode accessor throws when the node has the wrong kind, such as stringValue() on a number, or cannot be converted.

json library

Classes

Enums

Exceptions / Errors

spring_core_dart package

json library