Annotation Interface JsonTypeInfo
Some examples of typical annotations:
// Include Java class name ("com.myempl.ImplClass") as JSON property "class" @JsonTypeInfo(use=Id.CLASS, include=As.PROPERTY, property="class") // Include logical type name (defined in impl classes) as wrapper; 2 annotations @JsonTypeInfo(use=Id.NAME, include=As.WRAPPER_OBJECT) @JsonSubTypes({com.myemp.Impl1.class, com.myempl.Impl2.class})Alternatively you can also define fully customized type handling by using
@JsonTypeResolver
annotation (from databind package).
This annotation can be used both for types (classes) and properties. If both exist, annotation on property has precedence, as it is considered more specific.
When used for properties (fields, methods), this annotation applies
to values: so when applied to structure types
(like Collection
, Map
, arrays),
will apply to contained values, not the container;
for non-structured types there is no difference.
This is identical to how JAXB handles type information
annotations; and is chosen since it is the dominant use case.
There is no per-property way to force type information to be included
for type of container (structured type); for container types one has
to use annotation for type declaration.
Note on visibility of type identifier: by default, deserialization
(use during reading of JSON) of type identifier
is completely handled by Jackson, and is not passed to
deserializers. However, if so desired,
it is possible to define property visible = true
in which case property will be passed as-is to deserializers
(and set via setter or field) on deserialization.
On serialization side, Jackson will generate type id by itself,
except if there is a property with name that matches
property()
, in which case value of that property is
used instead.
NOTE: use of type id of "class name" with very general base type
(such as Object
or Serializable
)
can potentially open up security holes if deserializing content
generated by untrusted sources. If content can not be trusted,
it is necessary to either use "type name" as type id, or to
limit possible types using other means.
-
Nested Class Summary
Modifier and TypeClassDescriptionstatic enum
Definition of standard type inclusion mechanisms for type metadata.static enum
Definition of different type identifiers that can be included in JSON during serialization, and used for deserialization.static class
Deprecated. -
Required Element Summary
Modifier and TypeRequired ElementDescriptionSpecifies kind of type metadata to use when serializing type information for instances of annotated type and its subtypes; as well as what is expected during deserialization. -
Optional Element Summary
Modifier and TypeOptional ElementDescriptionClass<?>
Optional property that can be used to specify default implementation class to use for deserialization if type identifier is either not present, or can not be mapped to a registered type (which can occur for ids, but not when specifying explicit class to use).Specifies mechanism to use for including type metadata (if any; forJsonTypeInfo.Id.NONE
nothing is included); used when serializing, and expected when deserializing.Property names used when type inclusion method (JsonTypeInfo.As.PROPERTY
) is used (or possibly when using type metadata of typeJsonTypeInfo.Id.CUSTOM
).boolean
Property that defines whether type identifier value will be passed as part of JSON stream to deserializer (true), or handled and removed byTypeDeserializer
(false).
-
Element Details
-
use
JsonTypeInfo.Id useSpecifies kind of type metadata to use when serializing type information for instances of annotated type and its subtypes; as well as what is expected during deserialization.
-
-
-
include
JsonTypeInfo.As includeSpecifies mechanism to use for including type metadata (if any; forJsonTypeInfo.Id.NONE
nothing is included); used when serializing, and expected when deserializing.Note that for type metadata type of
JsonTypeInfo.Id.CUSTOM
, this setting may or may not have any effect.- Default:
- PROPERTY
-
property
String propertyProperty names used when type inclusion method (JsonTypeInfo.As.PROPERTY
) is used (or possibly when using type metadata of typeJsonTypeInfo.Id.CUSTOM
). If POJO itself has a property with same name, value of property will be set with type id metadata: if no such property exists, type id is only used for determining actual type.Default property name used if this property is not explicitly defined (or is set to empty
String
) is based on type metadata type (use()
) used.- Default:
- ""
-
defaultImpl
Class<?> defaultImplOptional property that can be used to specify default implementation class to use for deserialization if type identifier is either not present, or can not be mapped to a registered type (which can occur for ids, but not when specifying explicit class to use). Property has no effect on choice of type id used for serialization; it is only used in deciding what to do for otherwise unmappable cases.Note that while this property allows specification of the default implementation to use, it does not help with structural issues that may arise if type information is missing. This means that most often this is used with type-name -based resolution, to cover cases where new subtypes are added, but base type is not changed to reference new subtypes.
There are certain special values that indicate alternate behavior:
Void
means that objects with unmappable (or missing) type are to be mapped to null references. For backwards compatibility (2.5 and below), value ofedu.internet2.middleware.grouperClientExt.com.fasterxml.jackson.databind.annotation.NoClass
is also allowed for such usage.- Placeholder value of
JsonTypeInfo
(that is, this annotation type itself} means "there is no default implementation" (in which case an error results from unmappable type). For backwards compatibility with earlier versions (2.5 and below), value ofJsonTypeInfo.None
may also be used.
- Default:
- edu.internet2.middleware.grouperClientExt.com.fasterxml.jackson.annotation.JsonTypeInfo.class
-
visible
boolean visibleProperty that defines whether type identifier value will be passed as part of JSON stream to deserializer (true), or handled and removed byTypeDeserializer
(false). Property has no effect on serialization.Default value is false, meaning that Jackson handles and removes the type identifier from JSON content that is passed to
JsonDeserializer
.- Since:
- 2.0
- Default:
- false
-
JsonTypeInfo
), if such behavior is needed; this is rarely necessary.