Class ValueInstantiator

java.lang.Object
com.fasterxml.jackson.databind.deser.ValueInstantiator
Direct Known Subclasses:
StdValueInstantiator, ValueInstantiator.Base, ValueInstantiator.Delegating

public abstract class ValueInstantiator extends Object
Class that defines simple API implemented by objects that create value instances. Some or all of properties of value instances may be initialized by instantiator, rest being populated by deserializer, to which value instance is passed. Since different kinds of JSON values (structured and scalar) may be bound to Java values, in some cases instantiator fully defines resulting value; this is the case when JSON value is a scalar value (String, number, boolean).

Note that this type is not parameterized (even though it would seemingly make sense), because such type information cannot be use effectively during runtime: access is always using either wildcard type, or just basic Object; and so adding type parameter seems like unnecessary extra work.

Actual implementations are strongly recommended to be based on StdValueInstantiator which implements all methods, and as such will be compatible across versions even if new methods were added to this interface.

  • Constructor Details

    • ValueInstantiator

      public ValueInstantiator()
  • Method Details

    • createContextual

      public ValueInstantiator createContextual(DeserializationContext ctxt, BeanDescription beanDesc) throws JsonMappingException
      "Contextualization" method that is called after construction but before first use, to allow instantiator access to context needed to possible resolve its dependencies.
      Parameters:
      ctxt - Currently active deserialization context: needed to (for example) resolving TypeDeserializers.
      Returns:
      This instance, if no change, or newly constructed instance
      Throws:
      JsonMappingException - If there are issues with contextualization
      Since:
      2.12
    • getValueClass

      public Class<?> getValueClass()
      Accessor for raw (type-erased) type of instances to create.

      NOTE: since this method has not existed since beginning of Jackson 2.0 series, default implementation will just return Object.class; implementations are expected to override it with real value.

      Since:
      2.8
    • getValueTypeDesc

      public String getValueTypeDesc()
      Method that returns description of the value type this instantiator handles. Used for error messages, diagnostics.
    • canInstantiate

      public boolean canInstantiate()
      Method that will return true if any of canCreateXxx method returns true: that is, if there is any way that an instance could be created.
    • canCreateFromString

      public boolean canCreateFromString()
      Method that can be called to check whether a String-based creator is available for this instantiator.

      NOTE: does NOT include possible case of fallbacks, or coercion; only considers explicit creator.

    • canCreateFromInt

      public boolean canCreateFromInt()
      Method that can be called to check whether an integer (int, Integer) based creator is available to use (to call createFromInt(com.fasterxml.jackson.databind.DeserializationContext, int)).
    • canCreateFromLong

      public boolean canCreateFromLong()
      Method that can be called to check whether a long (long, Long) based creator is available to use (to call createFromLong(com.fasterxml.jackson.databind.DeserializationContext, long)).
    • canCreateFromBigInteger

      public boolean canCreateFromBigInteger()
      Method that can be called to check whether a BigInteger based creator is available to use (to call createFromBigInteger(com.fasterxml.jackson.databind.DeserializationContext, java.math.BigInteger)). +
    • canCreateFromDouble

      public boolean canCreateFromDouble()
      Method that can be called to check whether a double (double / Double) based creator is available to use (to call createFromDouble(com.fasterxml.jackson.databind.DeserializationContext, double)).
    • canCreateFromBigDecimal

      public boolean canCreateFromBigDecimal()
      Method that can be called to check whether a BigDecimal based creator is available to use (to call createFromBigDecimal(com.fasterxml.jackson.databind.DeserializationContext, java.math.BigDecimal)).
    • canCreateFromBoolean

      public boolean canCreateFromBoolean()
      Method that can be called to check whether a double (boolean / Boolean) based creator is available to use (to call createFromDouble(com.fasterxml.jackson.databind.DeserializationContext, double)).
    • canCreateUsingDefault

      public boolean canCreateUsingDefault()
      Method that can be called to check whether a default creator (constructor, or no-arg static factory method) is available for this instantiator
    • canCreateUsingDelegate

      public boolean canCreateUsingDelegate()
      Method that can be called to check whether a delegate-based creator (single-arg constructor or factory method) is available for this instantiator
    • canCreateUsingArrayDelegate

      public boolean canCreateUsingArrayDelegate()
      Method that can be called to check whether a array-delegate-based creator (single-arg constructor or factory method) is available for this instantiator
      Since:
      2.7
    • canCreateFromObjectWith

      public boolean canCreateFromObjectWith()
      Method that can be called to check whether a property-based creator (argument-taking constructor or factory method) is available to instantiate values from JSON Object
    • getFromObjectArguments

      public SettableBeanProperty[] getFromObjectArguments(DeserializationConfig config)
      Method called to determine types of instantiation arguments to use when creating instances with creator arguments (when canCreateFromObjectWith() returns true). These arguments are bound from JSON, using specified property types to locate deserializers.

      NOTE: all properties will be of type CreatorProperty.

    • getDelegateType

      public JavaType getDelegateType(DeserializationConfig config)
      Method that can be used to determine what is the type of delegate type to use, if any; if no delegates are used, will return null. If non-null type is returned, deserializer will bind JSON into specified type (using standard deserializer for that type), and pass that to instantiator.
    • getArrayDelegateType

      public JavaType getArrayDelegateType(DeserializationConfig config)
      Method that can be used to determine what is the type of array delegate type to use, if any; if no delegates are used, will return null. If non-null type is returned, deserializer will bind JSON into specified type (using standard deserializer for that type), and pass that to instantiator.
      Since:
      2.7
    • createUsingDefault

      public Object createUsingDefault(DeserializationContext ctxt) throws IOException
      Method called to create value instance from a JSON value when no data needs to passed to creator (constructor, factory method); typically this will call the default constructor of the value object. It will only be used if more specific creator methods are not applicable; hence "default".

      This method is called if getFromObjectArguments(com.fasterxml.jackson.databind.DeserializationConfig) returns null or empty List.

      Throws:
      IOException
    • createFromObjectWith

      public Object createFromObjectWith(DeserializationContext ctxt, Object[] args) throws IOException
      Method called to create value instance from JSON Object when instantiation arguments are passed; this is done, for example when passing information specified with "Creator" annotations.

      This method is called if getFromObjectArguments(com.fasterxml.jackson.databind.DeserializationConfig) returns a non-empty List of arguments.

      Throws:
      IOException
    • createFromObjectWith

      public Object createFromObjectWith(DeserializationContext ctxt, SettableBeanProperty[] props, PropertyValueBuffer buffer) throws IOException
      Method that delegates to createFromObjectWith(DeserializationContext, Object[]) by default, but can be overridden if the application should have customized behavior with respect to missing properties.

      The default implementation of this method uses PropertyValueBuffer.getParameters(SettableBeanProperty[]) to read and validate all properties in bulk, possibly substituting defaults for missing properties or throwing exceptions for missing properties. An overridden implementation of this method could, for example, use PropertyValueBuffer.hasParameter(SettableBeanProperty) and PropertyValueBuffer.getParameter(SettableBeanProperty) to safely read the present properties only, and to have some other behavior for the missing properties.

      Throws:
      IOException
      Since:
      2.8
    • createUsingDelegate

      public Object createUsingDelegate(DeserializationContext ctxt, Object delegate) throws IOException
      Method to called to create value instance from JSON Object using an intermediate "delegate" value to pass to createor method
      Throws:
      IOException
    • createUsingArrayDelegate

      public Object createUsingArrayDelegate(DeserializationContext ctxt, Object delegate) throws IOException
      Method to called to create value instance from JSON Array using an intermediate "delegate" value to pass to createor method
      Throws:
      IOException
    • createFromString

      public Object createFromString(DeserializationContext ctxt, String value) throws IOException
      Throws:
      IOException
    • createFromInt

      public Object createFromInt(DeserializationContext ctxt, int value) throws IOException
      Throws:
      IOException
    • createFromLong

      public Object createFromLong(DeserializationContext ctxt, long value) throws IOException
      Throws:
      IOException
    • createFromBigInteger

      public Object createFromBigInteger(DeserializationContext ctxt, BigInteger value) throws IOException
      Throws:
      IOException
    • createFromDouble

      public Object createFromDouble(DeserializationContext ctxt, double value) throws IOException
      Throws:
      IOException
    • createFromBigDecimal

      public Object createFromBigDecimal(DeserializationContext ctxt, BigDecimal value) throws IOException
      Throws:
      IOException
    • createFromBoolean

      public Object createFromBoolean(DeserializationContext ctxt, boolean value) throws IOException
      Throws:
      IOException
    • getDefaultCreator

      public AnnotatedWithParams getDefaultCreator()
      Method that can be called to try to access member (constructor, static factory method) that is used as the "default creator" (creator that is called without arguments; typically default [zero-argument] constructor of the type). Note that implementations not required to return actual object they use (or, they may use some other instantiation) method. That is, even if canCreateUsingDefault() returns true, this method may return null .
    • getDelegateCreator

      public AnnotatedWithParams getDelegateCreator()
      Method that can be called to try to access member (constructor, static factory method) that is used as the "delegate creator". Note that implementations not required to return actual object they use (or, they may use some other instantiation) method. That is, even if canCreateUsingDelegate() returns true, this method may return null .
    • getArrayDelegateCreator

      public AnnotatedWithParams getArrayDelegateCreator()
      Method that can be called to try to access member (constructor, static factory method) that is used as the "array delegate creator". Note that implementations not required to return actual object they use (or, they may use some other instantiation) method. That is, even if canCreateUsingArrayDelegate() returns true, this method may return null .
    • getWithArgsCreator

      public AnnotatedWithParams getWithArgsCreator()
      Method that can be called to try to access member (constructor, static factory method) that is used as the "non-default creator" (constructor or factory method that takes one or more arguments). Note that implementations not required to return actual object they use (or, they may use some other instantiation) method. That is, even if canCreateFromObjectWith() returns true, this method may return null .
    • _createFromStringFallbacks

      @Deprecated protected Object _createFromStringFallbacks(DeserializationContext ctxt, String value) throws IOException
      Deprecated.
      Since 2.12 should not handle coercions here
      Throws:
      IOException
      Since:
      2.4 (demoted from StdValueInstantiator)