public abstract class JsonDeserializer<T> extends Object
ObjectMapper
(and
other chained JsonDeserializer
s too) to deserialize Objects of
arbitrary types from JSON, using provided JsonParser
.Modifier and Type | Class and Description |
---|---|
static class |
JsonDeserializer.None
This marker class is only to be used with annotations, to
indicate that no deserializer is configured.
|
Constructor and Description |
---|
JsonDeserializer() |
Modifier and Type | Method and Description |
---|---|
abstract T |
deserialize(JsonParser jp,
DeserializationContext ctxt)
Method that can be called to ask implementation to deserialize
JSON content into the value type this serializer handles.
|
T |
deserialize(JsonParser jp,
DeserializationContext ctxt,
T intoValue)
Alternate deserialization method (compared to the most commonly
used,
deserialize(JsonParser, DeserializationContext) ),
which takes in initialized value instance, to be
configured and/or populated by deserializer. |
Object |
deserializeWithType(JsonParser jp,
DeserializationContext ctxt,
TypeDeserializer typeDeserializer)
Deserialization called when type being deserialized is defined to
contain additional type identifier, to allow for correctly
instantiating correct subtype.
|
T |
getEmptyValue()
Method called to determine value to be used for "empty" values
(most commonly when deserializing from empty JSON Strings).
|
T |
getNullValue()
Method that can be called to determine value to be used for
representing null values (values deserialized when JSON token
is
JsonToken.VALUE_NULL ). |
JsonDeserializer<T> |
unwrappingDeserializer()
Method that will return deserializer instance that is able
to handle "unwrapped" value instances
If no unwrapped instance can be constructed, will simply
return this object as-is.
|
public abstract T deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException
Pre-condition for this method is that the parser points to the first event that is part of value to deserializer (and which is never JSON 'null' literal, more on this below): for simple types it may be the only value; and for structured types the Object start marker. Post-condition is that the parser will point to the last event that is part of deserialized value (or in case deserialization fails, event that was not recognized or usable, which may be the same event as the one it pointed to upon call).
Note that this method is never called for JSON null literal, and thus deserializers need (and should) not check for it.
jp
- Parsed used for reading JSON contentctxt
- Context that can be used to access information about
this deserialization activity.IOException
JsonProcessingException
public T deserialize(JsonParser jp, DeserializationContext ctxt, T intoValue) throws IOException, JsonProcessingException
deserialize(JsonParser, DeserializationContext)
),
which takes in initialized value instance, to be
configured and/or populated by deserializer.
Method is not necessarily used for all supported types; most commonly
it is used
for Collections and Maps.
Default implementation just throws
UnsupportedOperationException
, to indicate that types
that do not explicitly add support do not expect to get the call.
IOException
JsonProcessingException
public Object deserializeWithType(JsonParser jp, DeserializationContext ctxt, TypeDeserializer typeDeserializer) throws IOException, JsonProcessingException
Default implementation may work for some types, but ideally subclasses should not rely on current default implementation. Implementation is mostly provided to avoid compilation errors with older code.
typeDeserializer
- Deserializer to use for handling type informationIOException
JsonProcessingException
public JsonDeserializer<T> unwrappingDeserializer()
Default implementation just returns 'this' indicating that no unwrapped variant exists
public T getNullValue()
JsonToken.VALUE_NULL
). Usually this is simply
Java null, but for some types (especially primitives) it may be
necessary to use non-null values.
Note that deserializers are allowed to call this just once and then reuse returned value; that is, method is not guaranteed to be called once for each conversion.
Default implementation simply returns null.
public T getEmptyValue()
getNullValue()
(which in turn
is usually simply Java null), but it can be overridden
for types. Or, if type should never be converted from empty
String, method can also throw an exception.
Default implementation simple calls getNullValue()
and
returns value.