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package com.fasterxml.jackson.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

/**
 * 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 {@link 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 {@link JsonValue} * (used for serialization). *
  • *
  • Constructor/factory method where every argument is annotated with * either {@link JsonProperty} or {@link JacksonInject}, to indicate name * of property to bind to *
  • *
* Also note that all {@link 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 {@link JsonValue}. *

* NOTE: As of Jackson 2.6, use of {@link JsonProperty#required()} is supported * for Creator methods (but not necessarily for regular setters or fields!). * * @see JsonProperty */ @Target({ElementType.ANNOTATION_TYPE, ElementType.METHOD, ElementType.CONSTRUCTOR}) @Retention(RetentionPolicy.RUNTIME) @JacksonAnnotation public @interface JsonCreator { /** * 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 {@link Mode} for more complete explanation of possible choices. *

* Default value of {@link Mode#DEFAULT} means that caller is to use standard * heuristics for choosing mode to use. * * @since 2.5 */ public Mode mode() default Mode.DEFAULT; /** * @since 2.5 */ public enum Mode { /** * Pseudo-mode that indicates that caller is to use default heuristics for * choosing mode to use. This typically favors use of delegating mode for * single-argument creators that take structured types. */ DEFAULT, /** * Mode that indicates that if creator takes a single argument, the whole incoming * data value is to be bound into declared type of that argument; this "delegate" * value is then passed as the argument to creator. */ DELEGATING, /** * Mode that indicates that the argument(s) for creator are to be bound from matching * properties of incoming Object value, using creator argument names (explicit or implicit) * to match incoming Object properties to arguments. *

* Note that this mode is currently (2.5) always used for multiple-argument creators; * the only ambiguous case is that of a single-argument creator. */ PROPERTIES, /** * Pseudo-mode that indicates that creator is not to be used. This can be used as a result * value for explicit disabling, usually either by custom annotation introspector, * or by annotation mix-ins (for example when choosing different creator). */ DISABLED } }





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