com.fasterxml.jackson.annotation.JsonValue Maven / Gradle / Ivy
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 indicates that the value of annotated accessor (either field
* or "getter" method [a method with non-void return type, no args])
* is to be used as the single value to serialize for the instance,
* instead of the usual method of collecting properties of value.
* Usually value will be of a simple scalar type
* (String or Number), but it can be any serializable type (Collection,
* Map or Bean).
*
* At most one accessor of a Class can be annotated with this annotation;
* if more than one is found, an exception may be thrown.
* Also, if method signature of annotated method is not compatible with Getters,
* an exception may be thrown (whether exception is thrown or not is an
* implementation detail (due to filtering during introspection, some annotations
* may be skipped) and applications should not rely on specific behavior).
*
* A typical usage is that of annotating toString()
* method so that returned String value is used as the JSON serialization;
* and if deserialization is needed, there is matching constructor
* or factory method annotated with {@link JsonCreator} annotation.
*
* Boolean argument is only used so that subclasses can "disable"
* annotation if necessary.
*
* NOTE: when use for Java enums, one additional feature is
* that value returned by annotated method is also considered to be the
* value to deserialize from, not just JSON String to serialize as.
* This is possible since set of Enum values is constant and it is possible
* to define mapping, but can not be done in general for POJO types; as such,
* this is not used for POJO deserialization.
*
* NOTE: When the instance is being serialized as the key of a Map type,
* this will be ignored if an accessor is annotated with
* {@link JsonKey}.
*
* @see JsonCreator
* @see JsonKey
*/
@Target({ElementType.ANNOTATION_TYPE, ElementType.METHOD,
ElementType.FIELD // since 2.9
})
@Retention(RetentionPolicy.RUNTIME)
@JacksonAnnotation
public @interface JsonValue
{
/**
* Optional argument that defines whether this annotation is active
* or not. The only use for value 'false' if for overriding purposes.
* Overriding may be necessary when used
* with "mix-in annotations" (aka "annotation overrides").
* For most cases, however, default value of "true" is just fine
* and should be omitted.
*/
boolean value() default true;
}