Package com.fasterxml.jackson.databind.deser.std

Class StdDelegatingDeserializer<T>

java.lang.Object

com.fasterxml.jackson.databind.JsonDeserializer<T>

com.fasterxml.jackson.databind.deser.std.StdDeserializer<T>

com.fasterxml.jackson.databind.deser.std.StdDelegatingDeserializer<T>

Type Parameters:

T - Target type to convert to, from delegate type

All Implemented Interfaces:

ContextualDeserializer, NullValueProvider, ResolvableDeserializer, ValueInstantiator.Gettable, java.io.Serializable

public class StdDelegatingDeserializer<T>
extends StdDeserializer<T>
implements ContextualDeserializer, ResolvableDeserializer

Deserializer implementation where given Java type is first deserialized by a standard Jackson deserializer into a delegate type; and then this delegate type is converted using a configured Converter into desired target type. Common delegate types to use are Map and JsonNode.

Note that although types (delegate, target) may be related, they must not be same; trying to do this will result in an exception.

Since 2.5 There is StdNodeBasedDeserializer that is a simplified version for cases where intermediate type is JsonNode

Since:

2.1

See Also:

StdNodeBasedDeserializer, Converter, Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class com.fasterxml.jackson.databind.JsonDeserializer

JsonDeserializer.None

Constructor Summary

Constructors

Constructor	Description
StdDelegatingDeserializer(Converter<?,T> converter)
StdDelegatingDeserializer(Converter<java.lang.Object,T> converter, JavaType delegateType, JsonDeserializer<?> delegateDeserializer)

Method Summary

Modifier and Type	Method	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.
T	deserialize(JsonParser p, DeserializationContext ctxt)	Method that can be called to ask implementation to deserialize JSON content into the value type this serializer handles.
T	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.
JsonDeserializer<?>	getDelegatee()	Accessor that can be used to determine if this deserializer uses another deserializer for actual deserialization, by delegating calls.
java.lang.Class<?>	handledType()	Method for accessing concrete physical type of values this deserializer produces.
LogicalType	logicalType()	Method for accessing logical type of values this deserializer produces.
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.

Methods inherited from class com.fasterxml.jackson.databind.deser.std.StdDeserializer

getValueClass, getValueInstantiator, getValueType, getValueType

Methods inherited from class com.fasterxml.jackson.databind.JsonDeserializer

deserializeWithType, findBackReference, getAbsentValue, getEmptyAccessPattern, getEmptyValue, getEmptyValue, getKnownPropertyNames, getNullAccessPattern, getNullValue, getNullValue, getObjectIdReader, isCachable, replaceDelegatee, unwrappingDeserializer

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

StdDelegatingDeserializer

public StdDelegatingDeserializer(Converter<?,T> converter)

StdDelegatingDeserializer

public StdDelegatingDeserializer(Converter<java.lang.Object,T> converter,
                                 JavaType delegateType,
                                 JsonDeserializer<?> delegateDeserializer)

Method Detail

resolve

public void resolve(DeserializationContext ctxt)
             throws JsonMappingException

Description copied from interface: ResolvableDeserializer

Method called after deserializer instance has been constructed (and registered as necessary by provider objects), but before it has returned it to the caller. Called object can then resolve its dependencies to other types, including self-references (direct or indirect).

Specified by:

resolve in interface ResolvableDeserializer

Parameters:

ctxt - Context to use for accessing configuration, resolving secondary deserializers

Throws:

JsonMappingException

createContextual

public JsonDeserializer<?> createContextual(DeserializationContext ctxt,
                                            BeanProperty property)
                                     throws JsonMappingException

Description copied from interface: ContextualDeserializer

Method called to see if a different (or differently configured) deserializer is needed to deserialize values of specified property. Note that instance that this method is called on is typically shared one and as a result method should NOT modify this instance but rather construct and return a new instance. This instance should only be returned as-is, in case it is already suitable for use.

Specified by:

createContextual in interface ContextualDeserializer

Parameters:

ctxt - Deserialization context to access configuration, additional deserializers that may be needed by this deserializer

property - 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)

Returns:

Deserializer to use for deserializing values of specified property; may be this instance or a new instance.

Throws:

JsonMappingException

getDelegatee

public JsonDeserializer<?> getDelegatee()

Description copied from class: JsonDeserializer

Accessor that can be used to determine if this deserializer uses another deserializer for actual deserialization, by delegating calls. If so, will return immediate delegate (which itself may delegate to further deserializers); otherwise will return null.

Overrides:

getDelegatee in class JsonDeserializer<T>

Returns:

Deserializer this deserializer delegates calls to, if null; null otherwise.

handledType

public java.lang.Class<?> handledType()

Description copied from class: JsonDeserializer

Method for accessing concrete physical type of values this deserializer produces. Note that this information is not guaranteed to be exact -- it may be a more generic (super-type) -- but it should not be incorrect (return a non-related type).

Default implementation will return null, which means almost same same as returning Object.class would; that is, that nothing is known about handled type.

Overrides:

handledType in class StdDeserializer<T>

Returns:

Physical type of values this deserializer produces, if known; null if not

logicalType

public LogicalType logicalType()

Description copied from class: JsonDeserializer

Method for accessing logical type of values this deserializer produces. Typically used for further configuring handling of values, for example, to find which coercions are legal.

Overrides:

logicalType in class JsonDeserializer<T>

Returns:

Logical type of values this deserializer produces, if known; null if not

supportsUpdate

public java.lang.Boolean supportsUpdate(DeserializationConfig config)

Description copied from class: JsonDeserializer

Introspection method that may be called to see whether deserializer supports update of an existing value (aka "merging") or not. Return value should either be 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.

Overrides:

supportsUpdate in class JsonDeserializer<T>

deserialize

public T deserialize(JsonParser p,
                     DeserializationContext ctxt)
              throws java.io.IOException

Description copied from class: JsonDeserializer

Method that can be called to ask implementation to deserialize JSON content into the value type this serializer handles. Returned instance is to be constructed by method itself.

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.

Specified by:

deserialize in class JsonDeserializer<T>

Parameters:

p - Parsed used for reading JSON content

ctxt - Context that can be used to access information about this deserialization activity.

Returns:

Deserialized value

Throws:

java.io.IOException

deserializeWithType

public java.lang.Object deserializeWithType(JsonParser p,
                                            DeserializationContext ctxt,
                                            TypeDeserializer typeDeserializer)
                                     throws java.io.IOException

Description copied from class: StdDeserializer

Base implementation that does not assume specific type inclusion mechanism. Sub-classes are expected to override this method if they are to handle type information.

Overrides:

deserializeWithType in class StdDeserializer<T>

typeDeserializer - Deserializer to use for handling type information

Throws:

java.io.IOException

deserialize

public T deserialize(JsonParser p,
                     DeserializationContext ctxt,
                     java.lang.Object intoValue)
              throws java.io.IOException

Description copied from class: JsonDeserializer

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. 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)

Overrides:

deserialize in class JsonDeserializer<T>

Throws:

java.io.IOException