Module tools.jackson.databind
Package tools.jackson.databind.deser.std

Class ReferenceTypeDeserializer<T>

java.lang.Object
tools.jackson.databind.ValueDeserializer<T>
tools.jackson.databind.deser.std.StdDeserializer<T>
tools.jackson.databind.deser.std.ReferenceTypeDeserializer<T>
All Implemented Interfaces:
NullValueProvider, ValueInstantiator.Gettable
Direct Known Subclasses:
AtomicReferenceDeserializer, Jdk8OptionalDeserializer
public abstract class ReferenceTypeDeserializer<T> extends StdDeserializer<T>
Base deserializer implementation for properties ReferenceType values. Implements most of functionality, only leaving couple of abstract methods for sub-classes to implement

  • Field Details

    • _fullType

      protected final JavaType _fullType
      Full type of property (or root value) for which this deserializer has been constructed and contextualized.

    • _valueInstantiator

      protected final ValueInstantiator _valueInstantiator

    • _valueTypeDeserializer

      protected final TypeDeserializer _valueTypeDeserializer

    • _valueDeserializer

      protected final ValueDeserializer<Object> _valueDeserializer

  • Constructor Details

  • Method Details

    • createContextual

      public ValueDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property)
      Description copied from class: ValueDeserializer
      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.
      Overrides:
      createContextual in class ValueDeserializer<T>
      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.

    • getNullAccessPattern

      public AccessPattern getNullAccessPattern()
      Null value varies dynamically (unlike with scalar types), so let's indicate this.
      Specified by:
      getNullAccessPattern in interface NullValueProvider
      Overrides:
      getNullAccessPattern in class ValueDeserializer<T>

    • getEmptyAccessPattern

      public AccessPattern getEmptyAccessPattern()
      Description copied from class: ValueDeserializer
      This method may be called in conjunction with calls to ValueDeserializer.getEmptyValue(DeserializationContext), to check whether it needs to be called just once (static values), or each time empty value is needed.
      Overrides:
      getEmptyAccessPattern in class ValueDeserializer<T>

    • withResolved

      protected abstract ReferenceTypeDeserializer<T> withResolved(TypeDeserializer typeDeser, ValueDeserializer<?> valueDeser)
      Mutant factory method called when changes are needed; should construct newly configured instance with new values as indicated.

      NOTE: caller has verified that there are changes, so implementations need NOT check if a new instance is needed.

    • getNullValue

      public abstract T getNullValue(DeserializationContext ctxt)
      Description copied from class: ValueDeserializer
      Method that can be called to determine value to be used for representing null values (values deserialized when JSON token is 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 ValueDeserializer.getNullAccessPattern() returns.

      Default implementation simply returns null.

      Specified by:
      getNullValue in interface NullValueProvider
      Overrides:
      getNullValue in class ValueDeserializer<T>

    • getEmptyValue

      public Object getEmptyValue(DeserializationContext ctxt)
      Description copied from class: ValueDeserializer
      Method called to determine value to be used for "empty" values (most commonly when deserializing from empty JSON Strings). Usually this is same as ValueDeserializer.getNullValue(tools.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 ValueDeserializer.getEmptyAccessPattern() returns.

      Default implementation simply calls ValueDeserializer.getNullValue(tools.jackson.databind.DeserializationContext) and returns value.

      Overrides:
      getEmptyValue in class ValueDeserializer<T>

    • getAbsentValue

      public Object getAbsentValue(DeserializationContext ctxt)
      Description copied from class: ValueDeserializer
      Method called to determine placeholder value to be used for cases where no value was obtained from input but we must pass a value nonetheless: the common case is that of Creator methods requiring passing a value for every parameter. Usually this is same as ValueDeserializer.getNullValue(tools.jackson.databind.DeserializationContext) (which in turn is usually simply Java null), but it can be overridden for specific types: most notable scalar types must use "default" values.

      This method needs to be called every time a determination is made.

      Default implementation simply calls ValueDeserializer.getNullValue(tools.jackson.databind.DeserializationContext) and returns value.

      Specified by:
      getAbsentValue in interface NullValueProvider
      Overrides:
      getAbsentValue in class ValueDeserializer<T>

    • referenceValue

      public abstract T referenceValue(Object contents)

    • updateReference

      public abstract T updateReference(T reference, Object contents)
      Method called in case of "merging update", in which we should try update reference instead of creating a new one. If this does not succeed, should just create a new instance.

    • getReferenced

      public abstract Object getReferenced(T reference)
      Method that may be called to find contents of specified reference, if any; or `null` if none. Note that method should never fail, so for types that use concept of "absence" vs "presence", `null` is to be returned for both "absent" and "reference to `null`" cases.

    • getValueInstantiator

      public ValueInstantiator getValueInstantiator()
      Specified by:
      getValueInstantiator in interface ValueInstantiator.Gettable
      Overrides:
      getValueInstantiator in class StdDeserializer<T>

    • getValueType

      public JavaType getValueType()
      Description copied from class: StdDeserializer
      Exact structured type this deserializer handles, if known.
      Overrides:
      getValueType in class StdDeserializer<T>

    • logicalType

      public LogicalType logicalType()
      Description copied from class: ValueDeserializer
      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 ValueDeserializer<T>
      Returns:
      Logical type of values this deserializer produces, if known; null if not

    • supportsUpdate

      public Boolean supportsUpdate(DeserializationConfig config)
      By default we assume that updateability mostly relies on value deserializer; if it supports updates, typically that's what matters. So let's just delegate.
      Overrides:
      supportsUpdate in class ValueDeserializer<T>

    • deserialize

      public T deserialize(JsonParser p, DeserializationContext ctxt) throws JacksonException
      Description copied from class: ValueDeserializer
      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).

      Handling null values (JsonToken.VALUE_NULL)
      : Note that this method is never called for the JSON null literal to avoid every deserializer from having to handle null values. Instead, the ValueDeserializer.getNullValue(DeserializationContext) method is called to produce a null value. To influence null handling, custom deserializers should override ValueDeserializer.getNullValue(DeserializationContext) and usually also ValueDeserializer.getNullAccessPattern().

      Specified by:
      deserialize in class ValueDeserializer<T>
      Parameters:
      p - Parser used for reading JSON content
      ctxt - Context that can be used to access information about this deserialization activity.
      Returns:
      Deserialized value
      Throws:
      JacksonException

    • deserialize

      public T deserialize(JsonParser p, DeserializationContext ctxt, T reference) throws JacksonException
      Description copied from class: ValueDeserializer
      Alternate deserialization method (compared to the most commonly used, ValueDeserializer.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 ValueDeserializer<T>
      Throws:
      JacksonException

    • deserializeWithType

      public Object deserializeWithType(JsonParser p, DeserializationContext ctxt, TypeDeserializer typeDeserializer) throws JacksonException
      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:
      JacksonException