public abstract class DelegatingDeserializer extends StdDeserializer<java.lang.Object> implements ContextualDeserializer, ResolvableDeserializer
JsonDeserializer
s
that mostly delegate functionality to another deserializer implementation
(possibly forming a chaing of deserializers delegating functionality
in some cases)JsonDeserializer.None
Constructor and Description |
---|
DelegatingDeserializer(JsonDeserializer<?> d) |
Modifier and Type | Method and Description |
---|---|
JsonDeserializer<?> |
createContextual(DeserializationContext ctxt,
BeanProperty property)
Method called to see if a different (or differently configured) deserializer
is needed to deserialize values of specified property.
|
java.lang.Object |
deserialize(JsonParser p,
DeserializationContext ctxt)
Method that can be called to ask implementation to deserialize
JSON content into the value type this serializer handles.
|
java.lang.Object |
deserialize(JsonParser p,
DeserializationContext ctxt,
java.lang.Object intoValue)
Alternate deserialization method (compared to the most commonly
used,
JsonDeserializer.deserialize(JsonParser, DeserializationContext) ),
which takes in initialized value instance, to be
configured and/or populated by deserializer. |
java.lang.Object |
deserializeWithType(JsonParser p,
DeserializationContext ctxt,
TypeDeserializer typeDeserializer)
Base implementation that does not assume specific type
inclusion mechanism.
|
SettableBeanProperty |
findBackReference(java.lang.String logicalName)
Method needed by
BeanDeserializerFactory to properly link
managed- and back-reference pairs. |
JsonDeserializer<?> |
getDelegatee()
Accessor that can be used to determine if this deserializer uses
another deserializer for actual deserialization, by delegating
calls.
|
java.lang.Object |
getEmptyValue(DeserializationContext ctxt)
Method called to determine value to be used for "empty" values
(most commonly when deserializing from empty JSON Strings).
|
java.util.Collection<java.lang.Object> |
getKnownPropertyNames()
Method that will
either return null to indicate that type being deserializers
has no concept of properties; or a collection of identifiers
for which
toString will give external property
name. |
AccessPattern |
getNullAccessPattern()
This method may be called in conjunction with calls to
JsonDeserializer.getNullValue(DeserializationContext) , to check whether it needs
to be called just once (static values), or each time empty value is
needed. |
java.lang.Object |
getNullValue(DeserializationContext ctxt)
Method that can be called to determine value to be used for
representing null values (values deserialized when JSON token
is
JsonToken.VALUE_NULL ). |
ObjectIdReader |
getObjectIdReader()
Accessor that can be used to check whether this deserializer
is expecting to possibly get an Object Identifier value instead of full value
serialization, and if so, should be able to resolve it to actual
Object instance to return as deserialized value.
|
boolean |
isCachable()
Method called to see if deserializer instance is cachable and
usable for other properties of same type (type for which instance
was created).
|
JsonDeserializer<?> |
replaceDelegatee(JsonDeserializer<?> delegatee)
Method that can be called to try to replace deserializer this deserializer
delegates calls to.
|
void |
resolve(DeserializationContext ctxt)
Method called after deserializer instance has been constructed
(and registered as necessary by provider objects),
but before it has returned it to the caller.
|
java.lang.Boolean |
supportsUpdate(DeserializationConfig config)
Introspection method that may be called to see whether deserializer supports
update of an existing value (aka "merging") or not.
|
getValueClass, getValueType, getValueType, handledType
deserializeWithType, getEmptyAccessPattern, getEmptyValue, getNullValue, unwrappingDeserializer
public DelegatingDeserializer(JsonDeserializer<?> d)
public void resolve(DeserializationContext ctxt) throws JsonMappingException
ResolvableDeserializer
resolve
in interface ResolvableDeserializer
ctxt
- Context to use for accessing configuration, resolving
secondary deserializersJsonMappingException
public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property) throws JsonMappingException
ContextualDeserializer
createContextual
in interface ContextualDeserializer
ctxt
- Deserialization context to access configuration, additional
deserializers that may be needed by this deserializerproperty
- Method, field or constructor parameter that represents the property
(and is used to assign deserialized value).
Should be available; but there may be cases where caller cannot provide it and
null is passed instead (in which case impls usually pass 'this' deserializer as is)JsonMappingException
public JsonDeserializer<?> replaceDelegatee(JsonDeserializer<?> delegatee)
JsonDeserializer
UnsupportedOperationException
(if operation does not
make sense or is not allowed); or return this deserializer as is.replaceDelegatee
in class JsonDeserializer<java.lang.Object>
public java.lang.Object deserialize(JsonParser p, DeserializationContext ctxt) throws java.io.IOException
JsonDeserializer
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 or a FIELD_NAME.
The two possible input conditions for structured types result from polymorphism via fields. In the ordinary case, Jackson calls this method when it has encountered an OBJECT_START, and the method implementation must advance to the next token to see the first field name. If the application configures polymorphism via a field, then the object looks like the following.
{ "@class": "class name", ... }Jackson consumes the two tokens (the @class field name and its value) in order to learn the class and select the deserializer. Thus, the stream is pointing to the FIELD_NAME for the first field after the @class. Thus, if you want your method to work correctly both with and without polymorphism, you must begin your method with:
if (p.currentToken() == JsonToken.START_OBJECT) { p.nextToken(); }This results in the stream pointing to the field name, so that the two conditions align.
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.
deserialize
in class JsonDeserializer<java.lang.Object>
p
- Parsed used for reading JSON contentctxt
- Context that can be used to access information about
this deserialization activity.java.io.IOException
public java.lang.Object deserialize(JsonParser p, DeserializationContext ctxt, java.lang.Object intoValue) throws java.io.IOException
JsonDeserializer
JsonDeserializer.deserialize(JsonParser, DeserializationContext)
),
which takes in initialized value instance, to be
configured and/or populated by deserializer.
Method is not necessarily used (or supported) by all types
(it will not work for immutable types, for obvious reasons):
most commonly it is used for Collections and Maps.
It may be used both with "updating readers" (for POJOs) and
when Collections and Maps use "getter as setter".
Default implementation just throws
UnsupportedOperationException
, to indicate that types
that do not explicitly add support do not necessarily support
update-existing-value operation (esp. immutable types)
deserialize
in class JsonDeserializer<java.lang.Object>
java.io.IOException
public java.lang.Object deserializeWithType(JsonParser p, DeserializationContext ctxt, TypeDeserializer typeDeserializer) throws java.io.IOException
StdDeserializer
deserializeWithType
in class StdDeserializer<java.lang.Object>
typeDeserializer
- Deserializer to use for handling type informationjava.io.IOException
public boolean isCachable()
JsonDeserializer
Note that cached instances are still resolved on per-property basis,
if instance implements ResolvableDeserializer
:
cached instance is just as the base. This means that in most cases it is safe to
cache instances; however, it only makes sense to cache instances
if instantiation is expensive, or if instances are heavy-weight.
Default implementation returns false, to indicate that no caching is done.
isCachable
in class JsonDeserializer<java.lang.Object>
public java.lang.Boolean supportsUpdate(DeserializationConfig config)
JsonDeserializer
Boolean.FALSE
if update is not supported at all (immutable values);
Boolean.TRUE
if update should usually work (regular POJOs, for example),
or null
if this is either not known, or may sometimes work.
Information gathered is typically used to either prevent merging update for
property (either by skipping, if based on global defaults; or by exception during
deserialization construction if explicit attempt made) if Boolean.FALSE
returned, or inclusion if Boolean.TRUE
is specified. If "unknown" case
(null
returned) behavior is to exclude property if global defaults
used; or to allow if explicit per-type or property merging is defined.
Default implementation returns null
to allow explicit per-type
or per-property attempts.
supportsUpdate
in class JsonDeserializer<java.lang.Object>
public JsonDeserializer<?> getDelegatee()
JsonDeserializer
getDelegatee
in class JsonDeserializer<java.lang.Object>
public SettableBeanProperty findBackReference(java.lang.String logicalName)
JsonDeserializer
BeanDeserializerFactory
to properly link
managed- and back-reference pairs.findBackReference
in class JsonDeserializer<java.lang.Object>
public AccessPattern getNullAccessPattern()
JsonDeserializer
JsonDeserializer.getNullValue(DeserializationContext)
, to check whether it needs
to be called just once (static values), or each time empty value is
needed.
Default implementation indicates that "null value" to use for input null is simply Java `null` for all deserializers, unless overridden by sub-classes. This information may be used as optimization.
getNullAccessPattern
in interface NullValueProvider
getNullAccessPattern
in class JsonDeserializer<java.lang.Object>
public java.lang.Object getNullValue(DeserializationContext ctxt) throws JsonMappingException
JsonDeserializer
JsonToken.VALUE_NULL
). Usually this is simply
Java null, but for some types (especially primitives) it may be
necessary to use non-null values.
This method may be called once, or multiple times, depending on what
JsonDeserializer.getNullAccessPattern()
returns.
Default implementation simply returns null.
getNullValue
in interface NullValueProvider
getNullValue
in class JsonDeserializer<java.lang.Object>
JsonMappingException
public java.lang.Object getEmptyValue(DeserializationContext ctxt) throws JsonMappingException
JsonDeserializer
JsonDeserializer.getNullValue(com.fasterxml.jackson.databind.DeserializationContext)
(which in turn
is usually simply Java null), but it can be overridden
for specific types. Or, if type should never be converted from empty
String, method can also throw an exception.
This method may be called once, or multiple times, depending on what
JsonDeserializer.getEmptyAccessPattern()
returns.
Default implementation simply calls JsonDeserializer.getNullValue(com.fasterxml.jackson.databind.DeserializationContext)
and
returns value.
getEmptyValue
in class JsonDeserializer<java.lang.Object>
JsonMappingException
public java.util.Collection<java.lang.Object> getKnownPropertyNames()
JsonDeserializer
toString
will give external property
name.
This is only to be used for error reporting and diagnostics
purposes (most commonly, to accompany "unknown property"
exception).getKnownPropertyNames
in class JsonDeserializer<java.lang.Object>
public ObjectIdReader getObjectIdReader()
JsonDeserializer
Default implementation returns null, as support cannot be implemented
generically. Some standard deserializers (most notably
BeanDeserializer
)
do implement this feature, and may return reader instance, depending on exact
configuration of instance (which is based on type, and referring property).
getObjectIdReader
in class JsonDeserializer<java.lang.Object>
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