Package com.fasterxml.jackson.annotation

Annotation Type JsonCreator

@Target({ANNOTATION_TYPE,METHOD,CONSTRUCTOR}) @Retention(RUNTIME) public @interface JsonCreator
Marker annotation that can be used to define constructors and factory methods as one to use for instantiating new instances of the associated class.

NOTE: when annotating creator methods (constructors, factory methods), method must either be:

  • Single-argument constructor/factory method without JsonProperty annotation for the argument: if so, this is so-called "delegate creator", in which case Jackson first binds JSON into type of the argument, and then calls creator. This is often used in conjunction with JsonValue (used for serialization).
  • Constructor/factory method where every argument is annotated with either JsonProperty or JacksonInject, to indicate name of property to bind to
Also note that all JsonProperty annotations must specify actual name (NOT empty String for "default") unless you use one of extension modules that can detect parameter name; this because default JDK versions before 8 have not been able to store and/or retrieve parameter names from bytecode. But with JDK 8 (or using helper libraries such as Paranamer, or other JVM languages like Scala or Kotlin), specifying name is optional.

One common use case is to use a delegating Creator to construct instances from scalar values (like java.lang.String) during deserialization, and serialize values using JsonValue.

NOTE: As of Jackson 2.6, use of JsonProperty.required() is supported for Creator methods (but not necessarily for regular setters or fields!).

See Also:

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static enum 
    JsonCreator.Mode
     

  • Optional Element Summary

    Optional Elements
    Modifier and Type
    Optional Element
    Description
    JsonCreator.Mode
    mode
    Property that is used to indicate how argument(s) is/are bound for creator, in cases there may be multiple alternatives.

  • Element Details

    • mode

      JsonCreator.Mode mode
      Property that is used to indicate how argument(s) is/are bound for creator, in cases there may be multiple alternatives. Currently the one case is that of a single-argument creator method, for which both so-called "delegating" and "property-based" bindings are possible: since delegating mode can not be used for multi-argument creators, the only choice there is "property-based" mode. Check JsonCreator.Mode for more complete explanation of possible choices.

      Default value of JsonCreator.Mode.DEFAULT means that caller is to use standard heuristics for choosing mode to use.

      Since:
      2.5
      Default:
      DEFAULT