org.codehaus.jackson.map

## Class MapperConfig<T extends MapperConfig<T>>

- java.lang.Object
- - org.codehaus.jackson.map.MapperConfig<T>

- All Implemented Interfaces:
    ClassIntrospector.MixInResolver
  Direct Known Subclasses:
    DeserializationConfig, SerializationConfig

      public abstract class MapperConfig<T extends MapperConfig<T>>
      extends Object
      implements ClassIntrospector.MixInResolver

  Interface that defines functionality accessible through both serialization and deserialization configuration objects; accessors to mode-independent configuration settings and such.

  As of version 1.9, the goal is to make this class eventually immutable. Because of this, existing methods that allow changing state of this instance are deprecated in favor of methods that create new instances with different configuration ("fluent factories"). One major remaining issue is that of handling mix-in annotations, which still represent a bit of mutable state; may need to implement a functional-style immutable map for storing those.

  Since:
    1.2 -- major change in 1.8, changed from interface to abstract class

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `MapperConfig.Base` Immutable container class used to store simple configuration settings.
    `static interface` | `MapperConfig.ConfigFeature` Interface that actual Feature enumerations used by `MapperConfig` implementations must implement.

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected MapperConfig.Base` | `_base` Immutable container object for simple configuration settings.
    `protected HashMap<ClassKey,Class<?>>` | `_mixInAnnotations` Mapping that defines how to apply mix-in annotations: key is the type to received additional annotations, and value is the type that has annotations to "mix in".
    `protected boolean` | `_mixInAnnotationsShared` Flag used to detect when a copy if mix-in annotations is needed: set when current copy is shared, cleared when a fresh copy is made
    `protected SubtypeResolver` | `_subtypeResolver` Registered concrete subtypes that can be used instead of (or in addition to) ones declared using annotations.
    `protected static DateFormat` | `DEFAULT_DATE_FORMAT` This is the default `DateFormat` used unless overridden by custom implementation.

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `MapperConfig(ClassIntrospector<? extends BeanDescription> ci, AnnotationIntrospector ai, VisibilityChecker<?> vc, SubtypeResolver str, PropertyNamingStrategy pns, TypeFactory tf, HandlerInstantiator hi)`
    `protected` | `MapperConfig(MapperConfig<T> src)` Simple copy constructor
    `protected` | `MapperConfig(MapperConfig<T> src, MapperConfig.Base base, SubtypeResolver str)`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addMixInAnnotations(Class<?> target, Class<?> mixinSource)` Method to use for adding mix-in annotations to use for augmenting specified class or interface.
    `void` | `appendAnnotationIntrospector(AnnotationIntrospector introspector)` Deprecated. Since 1.9 use `withAppendedAnnotationIntrospector(AnnotationIntrospector)` instead; this method is deprecated as it changes state, preventing immutability of instances
    `abstract boolean` | `canOverrideAccessModifiers()` Accessor for determining whether it is ok to try to force override of access modifiers to be able to get or set values of non-public Methods, Fields; to invoke non-public Constructors, Methods; or to instantiate non-public Classes.
    `JavaType` | `constructSpecializedType(JavaType baseType, Class<?> subclass)`
    `JavaType` | `constructType(Class<?> cls)` Helper method that will construct `JavaType` for given raw class.
    `JavaType` | `constructType(TypeReference<?> valueTypeRef)` Helper method that will construct `JavaType` for given type reference This is a simple short-cut for:
    `abstract T` | `createUnshared(SubtypeResolver subtypeResolver)` Method to use for constructing an instance that is not shared between multiple operations but only used for a single one (which may be this instance, if it is immutable; if not, a copy is constructed with same settings)
    `Class<?>` | `findMixInClassFor(Class<?> cls)` Method that will check if there are "mix-in" classes (with mix-in annotations) for given class
    `abstract void` | `fromAnnotations(Class<?> cls)` Deprecated. Since 1.9, it is preferably to explicitly configure instances; this method also modifies existing instance which is against immutable design goals of this class.
    `AnnotationIntrospector` | `getAnnotationIntrospector()` Method for getting `AnnotationIntrospector` configured to introspect annotation values used for configuration.
    `ClassIntrospector<? extends BeanDescription>` | `getClassIntrospector()`
    `DateFormat` | `getDateFormat()` Method for accessing currently configured (textual) date format that will be used for reading or writing date values (in case of writing, only if textual output is configured; not if dates are to be serialized as time stamps).
    `TypeResolverBuilder<?>` | `getDefaultTyper(JavaType baseType)` Method called to locate a type info handler for types that do not have one explicitly declared via annotations (or other configuration).
    `VisibilityChecker<?>` | `getDefaultVisibilityChecker()` Accessor for object used for determining whether specific property elements (method, constructors, fields) can be auto-detected based on their visibility (access modifiers).
    `HandlerInstantiator` | `getHandlerInstantiator()`
    `PropertyNamingStrategy` | `getPropertyNamingStrategy()`
    `SubtypeResolver` | `getSubtypeResolver()` Accessor for object used for finding out all reachable subtypes for supertypes; needed when a logical type name is used instead of class name (or custom scheme).
    `TypeFactory` | `getTypeFactory()`
    `void` | `insertAnnotationIntrospector(AnnotationIntrospector introspector)` Deprecated. Since 1.9 use `withInsertedAnnotationIntrospector(AnnotationIntrospector)` instead; this method is deprecated as it changes state, preventing immutability of instances
    `<DESC extends BeanDescription> DESC` | `introspectClassAnnotations(Class<?> cls)` Accessor for getting bean description that only contains class annotations: useful if no getter/setter/creator information is needed.
    `abstract <DESC extends BeanDescription> DESC` | `introspectClassAnnotations(JavaType type)` Accessor for getting bean description that only contains class annotations: useful if no getter/setter/creator information is needed.
    `<DESC extends BeanDescription> DESC` | `introspectDirectClassAnnotations(Class<?> cls)` Accessor for getting bean description that only contains immediate class annotations: ones from the class, and its direct mix-in, if any, but not from super types.
    `abstract <DESC extends BeanDescription> DESC` | `introspectDirectClassAnnotations(JavaType type)` Accessor for getting bean description that only contains immediate class annotations: ones from the class, and its direct mix-in, if any, but not from super types.
    `abstract boolean` | `isAnnotationProcessingEnabled()` Method for determining whether annotation processing is enabled or not (default settings are typically that it is enabled; must explicitly disable).
    `abstract boolean` | `isEnabled(MapperConfig.ConfigFeature f)` Method for checking whether given feature is enabled or not
    `int` | `mixInCount()`
    `void` | `setAnnotationIntrospector(AnnotationIntrospector ai)` Deprecated. Since 1.8, use either `withAnnotationIntrospector(AnnotationIntrospector)` or Module API instead
    `void` | `setDateFormat(DateFormat df)` Deprecated. As of version 1.8, it is preferable to call method in `ObjectMapper` instead; or construct new instance with `withDateFormat(DateFormat)`
    `void` | `setMixInAnnotations(Map<Class<?>,Class<?>> sourceMixins)` Method to use for defining mix-in annotations to use for augmenting annotations that processable (serializable / deserializable) classes have.
    `abstract boolean` | `shouldSortPropertiesAlphabetically()` Accessor for checking whether default settings for property handling indicate that properties should be alphabetically ordered or not.
    `TypeIdResolver` | `typeIdResolverInstance(Annotated annotated, Class<? extends TypeIdResolver> resolverClass)` Method that can be called to obtain an instance of `TypeIdResolver` of specified type.
    `TypeResolverBuilder<?>` | `typeResolverBuilderInstance(Annotated annotated, Class<? extends TypeResolverBuilder<?>> builderClass)` Method that can be called to obtain an instance of `TypeIdResolver` of specified type.
    `abstract T` | `withAnnotationIntrospector(AnnotationIntrospector ai)` Method for constructing and returning a new instance with different `AnnotationIntrospector` to use (replacing old one).
    `abstract T` | `withAppendedAnnotationIntrospector(AnnotationIntrospector introspector)` Method for constructing and returning a new instance with additional `AnnotationIntrospector` appended (as the lowest priority one)
    `abstract T` | `withClassIntrospector(ClassIntrospector<? extends BeanDescription> ci)` Method for constructing and returning a new instance with different `ClassIntrospector` to use.
    `abstract T` | `withDateFormat(DateFormat df)` Method for constructing and returning a new instance with different `DateFormat` to use.
    `abstract T` | `withHandlerInstantiator(HandlerInstantiator hi)` Method for constructing and returning a new instance with different `HandlerInstantiator` to use.
    `abstract T` | `withInsertedAnnotationIntrospector(AnnotationIntrospector introspector)` Method for constructing and returning a new instance with additional `AnnotationIntrospector` inserted (as the highest priority one)
    `abstract T` | `withPropertyNamingStrategy(PropertyNamingStrategy strategy)` Method for constructing and returning a new instance with different `PropertyNamingStrategy` to use.
    `abstract T` | `withSubtypeResolver(SubtypeResolver str)` Method for constructing and returning a new instance with different `SubtypeResolver` to use.
    `abstract T` | `withTypeFactory(TypeFactory typeFactory)` Method for constructing and returning a new instance with different `TypeFactory` to use.
    `abstract T` | `withTypeResolverBuilder(TypeResolverBuilder<?> trb)` Method for constructing and returning a new instance with different `TypeResolverBuilder` to use.
    `abstract T` | `withVisibility(JsonMethod forMethod, JsonAutoDetect.Visibility visibility)` Method for constructing and returning a new instance with different minimal visibility level for specified property type
    `abstract T` | `withVisibilityChecker(VisibilityChecker<?> vc)` Method for constructing and returning a new instance with different `VisibilityChecker` to use.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### DEFAULT_DATE_FORMAT

          protected static final DateFormat DEFAULT_DATE_FORMAT

      This is the default `DateFormat` used unless overridden by custom implementation.

    - #### _base

          protected MapperConfig.Base _base

      Immutable container object for simple configuration settings.

      Note: ideally this would be final, but until we can eliminate mutators, must keep it mutable.

    - #### _mixInAnnotations

          protected HashMap<ClassKey,Class<?>> _mixInAnnotations

      Mapping that defines how to apply mix-in annotations: key is the type to received additional annotations, and value is the type that has annotations to "mix in".

      Annotations associated with the value classes will be used to override annotations of the key class, associated with the same field or method. They can be further masked by sub-classes: you can think of it as injecting annotations between the target class and its sub-classes (or interfaces)

      Since:
        1.2

    - #### _mixInAnnotationsShared

          protected boolean _mixInAnnotationsShared

      Flag used to detect when a copy if mix-in annotations is needed: set when current copy is shared, cleared when a fresh copy is made
      Since:
        1.2

    - #### _subtypeResolver

          protected SubtypeResolver _subtypeResolver

      Registered concrete subtypes that can be used instead of (or in addition to) ones declared using annotations. Unlike most other settings, it is not configured as early as it is set, but rather only when a non-shared instance is constructed by `ObjectMapper` (or -Reader or -Writer)

      Note: this is the only property left as non-final, to allow lazy construction of the instance as necessary.

      Since:
        1.6

  - ### Constructor Detail

    - #### MapperConfig

          protected MapperConfig(ClassIntrospector<? extends BeanDescription> ci,
                      AnnotationIntrospector ai,
                      VisibilityChecker<?> vc,
                      SubtypeResolver str,
                      PropertyNamingStrategy pns,
                      TypeFactory tf,
                      HandlerInstantiator hi)

    - #### MapperConfig

          protected MapperConfig(MapperConfig<T> src)

      Simple copy constructor
      Since:
        1.8

    - #### MapperConfig

          protected MapperConfig(MapperConfig<T> src,
                      MapperConfig.Base base,
                      SubtypeResolver str)

      Since:
        1.8

  - ### Method Detail

    - #### fromAnnotations

          @Deprecated
          public abstract void fromAnnotations(Class<?> cls)

      Deprecated. Since 1.9, it is preferably to explicitly configure instances; this method also modifies existing instance which is against immutable design goals of this class.
      Method that checks class annotations that the argument Object has, and modifies settings of this configuration object accordingly, similar to how those annotations would affect actual value classes annotated with them, but with global scope. Note that not all annotations have global significance, and thus only subset of Jackson annotations will have any effect.

    - #### createUnshared

          public abstract T createUnshared(SubtypeResolver subtypeResolver)

      Method to use for constructing an instance that is not shared between multiple operations but only used for a single one (which may be this instance, if it is immutable; if not, a copy is constructed with same settings)
      Since:
        1.8

    - #### withClassIntrospector

          public abstract T withClassIntrospector(ClassIntrospector<? extends BeanDescription> ci)

      Method for constructing and returning a new instance with different `ClassIntrospector` to use.

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withAnnotationIntrospector

          public abstract T withAnnotationIntrospector(AnnotationIntrospector ai)

      Method for constructing and returning a new instance with different `AnnotationIntrospector` to use (replacing old one).

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withVisibilityChecker

          public abstract T withVisibilityChecker(VisibilityChecker<?> vc)

      Method for constructing and returning a new instance with different `VisibilityChecker` to use.

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withVisibility

          public abstract T withVisibility(JsonMethod forMethod,
                         JsonAutoDetect.Visibility visibility)

      Method for constructing and returning a new instance with different minimal visibility level for specified property type

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.9

    - #### withTypeResolverBuilder

          public abstract T withTypeResolverBuilder(TypeResolverBuilder<?> trb)

      Method for constructing and returning a new instance with different `TypeResolverBuilder` to use.

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withSubtypeResolver

          public abstract T withSubtypeResolver(SubtypeResolver str)

      Method for constructing and returning a new instance with different `SubtypeResolver` to use.

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withPropertyNamingStrategy

          public abstract T withPropertyNamingStrategy(PropertyNamingStrategy strategy)

      Method for constructing and returning a new instance with different `PropertyNamingStrategy` to use.

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withTypeFactory

          public abstract T withTypeFactory(TypeFactory typeFactory)

      Method for constructing and returning a new instance with different `TypeFactory` to use.

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withDateFormat

          public abstract T withDateFormat(DateFormat df)

      Method for constructing and returning a new instance with different `DateFormat` to use.

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withHandlerInstantiator

          public abstract T withHandlerInstantiator(HandlerInstantiator hi)

      Method for constructing and returning a new instance with different `HandlerInstantiator` to use.

      NOTE: make sure to register new instance with `ObjectMapper` if directly calling this method.

      Since:
        1.8

    - #### withInsertedAnnotationIntrospector

          public abstract T withInsertedAnnotationIntrospector(AnnotationIntrospector introspector)

      Method for constructing and returning a new instance with additional `AnnotationIntrospector` inserted (as the highest priority one)
      Since:
        1.9

    - #### withAppendedAnnotationIntrospector

          public abstract T withAppendedAnnotationIntrospector(AnnotationIntrospector introspector)

      Method for constructing and returning a new instance with additional `AnnotationIntrospector` appended (as the lowest priority one)
      Since:
        1.9

    - #### isEnabled

          public abstract boolean isEnabled(MapperConfig.ConfigFeature f)

      Method for checking whether given feature is enabled or not

    - #### isAnnotationProcessingEnabled

          public abstract boolean isAnnotationProcessingEnabled()

      Method for determining whether annotation processing is enabled or not (default settings are typically that it is enabled; must explicitly disable).
      Returns:
        True if annotation processing is enabled; false if not
      Since:
        1.8

    - #### canOverrideAccessModifiers

          public abstract boolean canOverrideAccessModifiers()

      Accessor for determining whether it is ok to try to force override of access modifiers to be able to get or set values of non-public Methods, Fields; to invoke non-public Constructors, Methods; or to instantiate non-public Classes. By default this is enabled, but on some platforms it needs to be prevented since if this would violate security constraints and cause failures.
      Returns:
        True if access modifier overriding is allowed (and may be done for any Field, Method, Constructor or Class); false to prevent any attempts to override.
      Since:
        1.8

    - #### shouldSortPropertiesAlphabetically

          public abstract boolean shouldSortPropertiesAlphabetically()

      Accessor for checking whether default settings for property handling indicate that properties should be alphabetically ordered or not.
      Since:
        1.9

    - #### getClassIntrospector

          public ClassIntrospector<? extends BeanDescription> getClassIntrospector()

    - #### getAnnotationIntrospector

          public AnnotationIntrospector getAnnotationIntrospector()

      Method for getting `AnnotationIntrospector` configured to introspect annotation values used for configuration.

      Non-final since it is actually overridden by sub-classes (for now?)

    - #### insertAnnotationIntrospector

          @Deprecated
          public final void insertAnnotationIntrospector(AnnotationIntrospector introspector)

      Deprecated. Since 1.9 use `withInsertedAnnotationIntrospector(AnnotationIntrospector)` instead; this method is deprecated as it changes state, preventing immutability of instances
      Method for registering specified `AnnotationIntrospector` as the highest priority introspector (will be chained with existing introspector(s) which will be used as fallbacks for cases this introspector does not handle)
      Parameters:
        `introspector` - Annotation introspector to register.
      Since:
        1.7

    - #### appendAnnotationIntrospector

          @Deprecated
          public final void appendAnnotationIntrospector(AnnotationIntrospector introspector)

      Deprecated. Since 1.9 use `withAppendedAnnotationIntrospector(AnnotationIntrospector)` instead; this method is deprecated as it changes state, preventing immutability of instances
      Method for registering specified `AnnotationIntrospector` as the lowest priority introspector, chained with existing introspector(s) and called as fallback for cases not otherwise handled.
      Parameters:
        `introspector` - Annotation introspector to register.
      Since:
        1.7

    - #### getDefaultVisibilityChecker

          public VisibilityChecker<?> getDefaultVisibilityChecker()

      Accessor for object used for determining whether specific property elements (method, constructors, fields) can be auto-detected based on their visibility (access modifiers). Can be changed to allow different minimum visibility levels for auto-detection. Note that this is the global handler; individual types (classes) can further override active checker used (using `JsonAutoDetect` annotation)
      Since:
        1.5

    - #### getPropertyNamingStrategy

          public final PropertyNamingStrategy getPropertyNamingStrategy()

      Since:
        1.8

    - #### getHandlerInstantiator

          public final HandlerInstantiator getHandlerInstantiator()

      Since:
        1.8

    - #### setMixInAnnotations

          public final void setMixInAnnotations(Map<Class<?>,Class<?>> sourceMixins)

      Method to use for defining mix-in annotations to use for augmenting annotations that processable (serializable / deserializable) classes have. Mixing in is done when introspecting class annotations and properties. Map passed contains keys that are target classes (ones to augment with new annotation overrides), and values that are source classes (have annotations to use for augmentation). Annotations from source classes (and their supertypes) will override annotations that target classes (and their super-types) have.
      Since:
        1.2

    - #### addMixInAnnotations

          public final void addMixInAnnotations(Class<?> target,
                                 Class<?> mixinSource)

      Method to use for adding mix-in annotations to use for augmenting specified class or interface. All annotations from `mixinSource` are taken to override annotations that `target` (or its supertypes) has.
      Parameters:
        `target` - Class (or interface) whose annotations to effectively override
        `mixinSource` - Class (or interface) whose annotations are to be "added" to target's annotations, overriding as necessary
      Since:
        1.2

    - #### findMixInClassFor

          public final Class<?> findMixInClassFor(Class<?> cls)

      Method that will check if there are "mix-in" classes (with mix-in annotations) for given class
      Specified by:
        `findMixInClassFor` in interface `ClassIntrospector.MixInResolver`
      Since:
        1.2

    - #### mixInCount

          public final int mixInCount()

      Since:
        1.8.1

    - #### getDefaultTyper

          public final TypeResolverBuilder<?> getDefaultTyper(JavaType baseType)

      Method called to locate a type info handler for types that do not have one explicitly declared via annotations (or other configuration). If such default handler is configured, it is returned; otherwise null is returned.
      Since:
        1.5

    - #### getSubtypeResolver

          public final SubtypeResolver getSubtypeResolver()

      Accessor for object used for finding out all reachable subtypes for supertypes; needed when a logical type name is used instead of class name (or custom scheme).
      Since:
        1.6

    - #### getTypeFactory

          public final TypeFactory getTypeFactory()

      Since:
        1.8

    - #### constructType

          public final JavaType constructType(Class<?> cls)

      Helper method that will construct `JavaType` for given raw class. This is a simple short-cut for:

              getTypeFactory().constructType(cls);

      Since:
        1.8

    - #### constructType

          public final JavaType constructType(TypeReference<?> valueTypeRef)

      Helper method that will construct `JavaType` for given type reference This is a simple short-cut for:

              getTypeFactory().constructType(valueTypeRef);

      Since:
        1.9

    - #### constructSpecializedType

          public JavaType constructSpecializedType(JavaType baseType,
                                          Class<?> subclass)

      Since:
        1.9.1

    - #### getDateFormat

          public final DateFormat getDateFormat()

      Method for accessing currently configured (textual) date format that will be used for reading or writing date values (in case of writing, only if textual output is configured; not if dates are to be serialized as time stamps).

      Note that typically `DateFormat` instances are not thread-safe (at least ones provided by JDK): this means that calling code should clone format instance before using it.

      This method is usually only called by framework itself, since there are convenience methods available via `DeserializationContext` and `SerializerProvider` that take care of cloning and thread-safe reuse.

    - #### introspectClassAnnotations

          public <DESC extends BeanDescription> DESC introspectClassAnnotations(Class<?> cls)

      Accessor for getting bean description that only contains class annotations: useful if no getter/setter/creator information is needed.
      Since:
        1.7

    - #### introspectClassAnnotations

          public abstract <DESC extends BeanDescription> DESC introspectClassAnnotations(JavaType type)

      Accessor for getting bean description that only contains class annotations: useful if no getter/setter/creator information is needed.
      Since:
        1.9

    - #### introspectDirectClassAnnotations

          public <DESC extends BeanDescription> DESC introspectDirectClassAnnotations(Class<?> cls)

      Accessor for getting bean description that only contains immediate class annotations: ones from the class, and its direct mix-in, if any, but not from super types.
      Since:
        1.7

    - #### introspectDirectClassAnnotations

          public abstract <DESC extends BeanDescription> DESC introspectDirectClassAnnotations(JavaType type)

      Accessor for getting bean description that only contains immediate class annotations: ones from the class, and its direct mix-in, if any, but not from super types.

    - #### typeResolverBuilderInstance

          public TypeResolverBuilder<?> typeResolverBuilderInstance(Annotated annotated,
                                                           Class<? extends TypeResolverBuilder<?>> builderClass)

      Method that can be called to obtain an instance of `TypeIdResolver` of specified type.
      Since:
        1.8

    - #### typeIdResolverInstance

          public TypeIdResolver typeIdResolverInstance(Annotated annotated,
                                              Class<? extends TypeIdResolver> resolverClass)

      Method that can be called to obtain an instance of `TypeIdResolver` of specified type.
      Since:
        1.8

    - #### setAnnotationIntrospector

          @Deprecated
          public final void setAnnotationIntrospector(AnnotationIntrospector ai)

      Deprecated. Since 1.8, use either `withAnnotationIntrospector(AnnotationIntrospector)` or Module API instead
      Method for replacing existing annotation introspector(s) with specified introspector. Since this method modifies state of configuration object directly, its use is not recommended.

    - #### setDateFormat

          @Deprecated
          public void setDateFormat(DateFormat df)

      Deprecated. As of version 1.8, it is preferable to call method in `ObjectMapper` instead; or construct new instance with `withDateFormat(DateFormat)`
      Method that will define specific date format to use for reading/writing Date and Calendar values. If null is passed, will use `StdDateFormat`. Instance is used as is, without creating a clone. Format object in use can be accessed using `getDateFormat()`.
      Parameters:
        `df` - Date format to use, if not null; if null, the default format will be used