@Target(value={ANNOTATION_TYPE,FIELD,METHOD,PARAMETER}) @Retention(value=RUNTIME) public @interface JsonMerge
Merging is only option if there is a way to introspect current state:
if there is accessor (getter, field) to use.
Merging can not be enabled if no accessor exists
or if assignment occurs using a Creator setter (constructor
or factory method), since there is no instance with state to introspect.
Merging also only has actual effect for structured types where there is an
obvious way to update a state (for example, POJOs have default values for properties,
and Collection
s and Map
s may have existing
elements; whereas scalar types do not such state: an int
has a value,
but no obvious and non-ambiguous way to merge state.
Merging is applied by using a deserialization method that accepts existing state
as an argument: it is then up to JsonDeserializer
implementation
to use that base state in a way that makes sense without further configuration.
For structured types this is usually obvious; and for scalar types not -- if
no obvious method exists, merging is not allowed; deserializer may choose to
either quietly ignore it, or throw an exception.
Note that use of merging usually adds some processing overhead since it adds an extra step of accessing the current state before assignment.
Note also that "root values" (values directly deserialized and not reached
via POJO properties) can not use this annotation; instead, ObjectMapper
and Object
have "updating reader" operations.
Default value is OptBoolean.TRUE
, that is, merging is enabled.
Modifier and Type | Optional Element and Description |
---|---|
OptBoolean |
value
Whether merging should or should not be enabled for the annotated property.
|
public abstract OptBoolean value
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