org.codehaus.jackson.annotate
Annotation Type JsonTypeInfo


@Target(value={TYPE,FIELD,METHOD,PARAMETER})
@Retention(value=RUNTIME)
public @interface JsonTypeInfo

Annotation used for configuring details of if and how type information is used with JSON serialization and deserialization, to preserve information about actual class of Object instances. This is necessarily for polymorphic types, and may also be needed to link abstract declared types and matching concrete implementation.

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.

NOTE: originally this annotation was only available to use with types (classes), but starting with 1.7, it is also allowed for properties (fields, methods, constructor parameters).

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.

Since:
1.5 (but available to fields, methods and constructor parameters since 1.7)
Author:
tatu
See Also:
JsonTypeResolver

Required Element Summary
 JsonTypeInfo.Id use
          What kind of type metadata is to be used for serializing and deserializing type information for instances of annotated type (and its subtypes unless overridden)
 
Optional Element Summary
 Class<?> defaultImpl
          Optional property that can be used to specify default implementation class to use 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).
 JsonTypeInfo.As include
          What mechanism is used for including type metadata (if any; for JsonTypeInfo.Id.NONE nothing is included).
 String property
          Property names used when type inclusion method (JsonTypeInfo.As.PROPERTY) is used (or possibly when using type metadata of type JsonTypeInfo.Id.CUSTOM).
 

Element Detail

use

public abstract JsonTypeInfo.Id use
What kind of type metadata is to be used for serializing and deserializing type information for instances of annotated type (and its subtypes unless overridden)

include

public abstract JsonTypeInfo.As include
What mechanism is used for including type metadata (if any; for JsonTypeInfo.Id.NONE nothing is included). Default

Note that for type metadata type of JsonTypeInfo.Id.CUSTOM, this setting may or may not have any effect.

Default:
org.codehaus.jackson.annotate.JsonTypeInfo.As.PROPERTY

property

public abstract String property
Property names used when type inclusion method (JsonTypeInfo.As.PROPERTY) is used (or possibly when using type metadata of type JsonTypeInfo.Id.CUSTOM).

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

public abstract Class<?> defaultImpl
Optional property that can be used to specify default implementation class to use 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).

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 sub-types are added, but base type is not changed to reference new sub-types.

Since:
1.9
Default:
org.codehaus.jackson.annotate.JsonTypeInfo.None.class