com.fasterxml.jackson.core/jackson-databind/2.9.5 : com/fasterxml/jackson/databind/SerializationFeature.java

SerializationFeature
http://github.com/FasterXML/jackson: General data-binding functionality for Jackson: works on core streaming API (FasterXML)
The Apache Software License, Version 2.0
Tatu Saloranta
Christopher Currie
Paul Brown
package com.fasterxml.jackson.databind;

import com.fasterxml.jackson.databind.cfg.ConfigFeature;

Enumeration that defines simple on/off features that affect
the way Java objects are serialized.
 Note that features can be set both through ObjectMapper (as sort of defaults) and through ObjectWriter. In first case these defaults must follow "config-then-use" patterns (i.e. defined once, not changed afterwards); all per-call changes must be done using ObjectWriter. /**
 * Enumeration that defines simple on/off features that affect
 * the way Java objects are serialized.
 *<p>
 * Note that features can be set both through
 * {@link ObjectMapper} (as sort of defaults) and through
 * {@link ObjectWriter}.
 * In first case these defaults must follow "config-then-use" patterns
 * (i.e. defined once, not changed afterwards); all per-call
 * changes must be done using {@link ObjectWriter}.
 */
public enum SerializationFeature implements ConfigFeature
{
    /*
    /******************************************************
    /* Generic output features
    /******************************************************
     */

    Feature that can be enabled to make root value (usually JSON
Object but can be any type) wrapped within a single property
JSON object, where key as the "root name", as determined by
annotation introspector (esp. for JAXB that uses
@XmlRootElement.name) or fallback (non-qualified
class name).
Feature is mostly intended for JAXB compatibility.

Feature is disabled by default.
/**
     * Feature that can be enabled to make root value (usually JSON
     * Object but can be any type) wrapped within a single property
     * JSON object, where key as the "root name", as determined by
     * annotation introspector (esp. for JAXB that uses
     * <code>@XmlRootElement.name</code>) or fallback (non-qualified
     * class name).
     * Feature is mostly intended for JAXB compatibility.
     *<p>
     * Feature is disabled by default.
     */
    WRAP_ROOT_VALUE(false),

    Feature that allows enabling (or disabling) indentation for the underlying generator, using the default pretty printer configured for ObjectMapper (and ObjectWriters created from mapper).  Note that the default pretty printer is only used if no explicit PrettyPrinter has been configured for the generator or ObjectWriter. 

Feature is disabled by default.
/**
     * Feature that allows enabling (or disabling) indentation
     * for the underlying generator, using the default pretty
     * printer configured for {@link ObjectMapper} (and
     * {@link ObjectWriter}s created from mapper).
     *<p>
     * Note that the default pretty printer is only used if
     * no explicit {@link com.fasterxml.jackson.core.PrettyPrinter} has been configured
     * for the generator or {@link ObjectWriter}.
     *<p>
     * Feature is disabled by default.
     */
    INDENT_OUTPUT(false),

    /*
    /******************************************************
    /* Error handling features
    /******************************************************
     */

    Feature that determines what happens when no accessors are
found for a type (and there are no annotations to indicate
it is meant to be serialized). If enabled (default), an
exception is thrown to indicate these as non-serializable
types; if disabled, they are serialized as empty Objects,
i.e. without any properties.

Note that empty types that this feature has only effect on
those "empty" beans that do not have any recognized annotations
(like @JsonSerialize): ones that do have annotations
do not result in an exception being thrown.

Feature is enabled by default.
/**
     * Feature that determines what happens when no accessors are
     * found for a type (and there are no annotations to indicate
     * it is meant to be serialized). If enabled (default), an
     * exception is thrown to indicate these as non-serializable
     * types; if disabled, they are serialized as empty Objects,
     * i.e. without any properties.
     *<p>
     * Note that empty types that this feature has only effect on
     * those "empty" beans that do not have any recognized annotations
     * (like <code>@JsonSerialize</code>): ones that do have annotations
     * do not result in an exception being thrown.
     *<p>
     * Feature is enabled by default.
     */
    FAIL_ON_EMPTY_BEANS(true),

    Feature that determines what happens when a direct self-reference is detected by a POJO (and no Object Id handling is enabled for it): either a JsonMappingException is thrown (if true), or reference is normally processed (false). 
Feature is enabled by default.
Since: 2.4/**
     * Feature that determines what happens when a direct self-reference
     * is detected by a POJO (and no Object Id handling is enabled for it):
     * either a {@link JsonMappingException} is
     * thrown (if true), or reference is normally processed (false).
     *<p>
     * Feature is enabled by default.
     *
     * @since 2.4
     */
    FAIL_ON_SELF_REFERENCES(true),

    Feature that determines whether Jackson code should catch and wrap Exceptions (but never Errors!) to add additional information about location (within input) of problem or not. If enabled, most exceptions will be caught and re-thrown (exception specifically being that IOExceptions may be passed as is, since they are declared as throwable); this can be convenient both in that all exceptions will be checked and declared, and so there is more contextual information. However, sometimes calling application may just want "raw" unchecked exceptions passed as is. 

Feature is enabled by default.
/**
     * Feature that determines whether Jackson code should catch
     * and wrap {@link Exception}s (but never {@link Error}s!)
     * to add additional information about
     * location (within input) of problem or not. If enabled,
     * most exceptions will be caught and re-thrown (exception
     * specifically being that {@link java.io.IOException}s may be passed
     * as is, since they are declared as throwable); this can be
     * convenient both in that all exceptions will be checked and
     * declared, and so there is more contextual information.
     * However, sometimes calling application may just want "raw"
     * unchecked exceptions passed as is.
     *<p>
     *<p>
     * Feature is enabled by default.
     */
    WRAP_EXCEPTIONS(true),

    Feature that determines what happens when an object which normally has type information included by Jackson is used in conjunction with JsonUnwrapped. In the default (enabled) state, an error will be thrown when an unwrapped object has type information. When disabled, the object will be unwrapped and the type information discarded. 
Feature is enabled by default.
Since: 2.4/**
     * Feature that determines what happens when an object which
     * normally has type information included by Jackson is used
     * in conjunction with {@link com.fasterxml.jackson.annotation.JsonUnwrapped}.
     * In the default (enabled) state, an error will be thrown when
     * an unwrapped object has type information. When disabled, the
     * object will be unwrapped and the type information discarded.
     *<p>
     * Feature is enabled by default.
     *
     * @since 2.4
     */
    FAIL_ON_UNWRAPPED_TYPE_IDENTIFIERS(true),

    /*
    /******************************************************
    /* Output life cycle features
    /******************************************************
     */

     Feature that determines whether close method of
serialized root level objects (ones for which ObjectMapper's writeValue() (or equivalent) method is called) that implement Closeable is called after serialization or not. If enabled, close() will
be called after serialization completes (whether succesfully, or
due to an error manifested by an exception being thrown). You can
think of this as sort of "finally" processing.

NOTE: only affects behavior with root objects, and not other
objects reachable from the root object. Put another way, only one
call will be made for each 'writeValue' call.

Feature is disabled by default.
/**
      * Feature that determines whether <code>close</code> method of
      * serialized <b>root level</b> objects (ones for which <code>ObjectMapper</code>'s
      * writeValue() (or equivalent) method is called)
      * that implement {@link java.io.Closeable}
      * is called after serialization or not. If enabled, <b>close()</b> will
      * be called after serialization completes (whether succesfully, or
      * due to an error manifested by an exception being thrown). You can
      * think of this as sort of "finally" processing.
      *<p>
      * NOTE: only affects behavior with <b>root</b> objects, and not other
      * objects reachable from the root object. Put another way, only one
      * call will be made for each 'writeValue' call.
     *<p>
     * Feature is disabled by default.
      */
    CLOSE_CLOSEABLE(false),

    Feature that determines whether JsonGenerator.flush() is
called after writeValue() method that takes JsonGenerator
as an argument completes (i.e. does NOT affect methods that use other destinations); same for methods in ObjectWriter. This usually makes sense; but there are cases where flushing should not be forced: for example when underlying stream is compressing and flush() causes compression state to be flushed (which occurs with some compression codecs). 
Feature is enabled by default.
/**
     * Feature that determines whether <code>JsonGenerator.flush()</code> is
     * called after <code>writeValue()</code> method <b>that takes JsonGenerator
     * as an argument</b> completes (i.e. does NOT affect methods
     * that use other destinations); same for methods in {@link ObjectWriter}.
     * This usually makes sense; but there are cases where flushing
     * should not be forced: for example when underlying stream is
     * compressing and flush() causes compression state to be flushed
     * (which occurs with some compression codecs).
     *<p>
     * Feature is enabled by default.
     */
    FLUSH_AFTER_WRITE_VALUE(true),

    /*
    /******************************************************
    /* Datatype-specific serialization configuration
    /******************************************************
     */

    Feature that determines whether Date (and date/time) values (and Date-based things like Calendars) are to be serialized as numeric timestamps (true; the default), or as something else (usually textual representation). If textual representation is used, the actual format is one returned by a call to MapperConfig<SerializationConfig>.getDateFormat: the default setting being StdDateFormat, which corresponds to format String of "yyyy-MM-dd'T'HH:mm:ss.SSSZ" (see DateFormat for details of format Strings). 
Note: whether this feature affects handling of other date-related
types depend on handlers of those types, although ideally they
should use this feature
 Note: whether Map keys are serialized as Strings or not is controlled using WRITE_DATE_KEYS_AS_TIMESTAMPS. 

Feature is enabled by default, so that date/time are by default
serialized as timestamps.
/**
     * Feature that determines whether Date (and date/time) values
     * (and Date-based things like {@link java.util.Calendar}s) are to be
     * serialized as numeric timestamps (true; the default),
     * or as something else (usually textual representation).
     * If textual representation is used, the actual format is
     * one returned by a call to
     * {@link com.fasterxml.jackson.databind.SerializationConfig#getDateFormat}:
     * the default setting being {@link com.fasterxml.jackson.databind.util.StdDateFormat},
     * which corresponds to format String of "yyyy-MM-dd'T'HH:mm:ss.SSSZ"
     * (see {@link java.text.DateFormat} for details of format Strings).
     *<p>
     * Note: whether this feature affects handling of other date-related
     * types depend on handlers of those types, although ideally they
     * should use this feature
     *<p>
     * Note: whether {@link java.util.Map} keys are serialized as Strings
     * or not is controlled using {@link #WRITE_DATE_KEYS_AS_TIMESTAMPS}.
     *<p>
     * Feature is enabled by default, so that date/time are by default
     * serialized as timestamps.
     */
    WRITE_DATES_AS_TIMESTAMPS(true),

    Feature that determines whether Dates (and sub-types) used as Map keys are serialized as timestamps or not (if not, will be serialized as textual values). 
Default value is 'false', meaning that Date-valued Map keys are serialized
as textual (ISO-8601) values.

Feature is disabled by default.
/**
     * Feature that determines whether {@link java.util.Date}s
     * (and sub-types) used as {@link java.util.Map} keys are serialized
     * as timestamps or not (if not, will be serialized as textual
     * values).
     *<p>
     * Default value is 'false', meaning that Date-valued Map keys are serialized
     * as textual (ISO-8601) values.
     *<p>
     * Feature is disabled by default.
     */
    WRITE_DATE_KEYS_AS_TIMESTAMPS(false),

    Feature that determines whether date/date-time values should be serialized
so that they include timezone id, in cases where type itself contains
timezone information. Including this information may lead to compatibility
issues because ISO-8601 specification does not define formats that include
such information.

If enabled, Timezone id should be included using format specified
with Java 8 DateTimeFormatter#ISO_ZONED_DATE_TIME definition
(for example, '2011-12-03T10:15:30+01:00[Europe/Paris]').

Note: setting has no relevance if date/time values are serialized as timestamps.

Feature is disabled by default, so that zone id is NOT included; rather, timezone
offset is used for ISO-8601 compatibility (if any timezone information is
included in value).
Since: 2.6/**
     * Feature that determines whether date/date-time values should be serialized
     * so that they include timezone id, in cases where type itself contains
     * timezone information. Including this information may lead to compatibility
     * issues because ISO-8601 specification does not define formats that include
     * such information.
     *<p>
     * If enabled, Timezone id should be included using format specified
     * with Java 8 <code>DateTimeFormatter#ISO_ZONED_DATE_TIME</code> definition
     * (for example, '2011-12-03T10:15:30+01:00[Europe/Paris]').
     *<p>
     * Note: setting has no relevance if date/time values are serialized as timestamps.
     *<p>
     * Feature is disabled by default, so that zone id is NOT included; rather, timezone
     * offset is used for ISO-8601 compatibility (if any timezone information is
     * included in value).
     * 
     * @since 2.6
     */
    WRITE_DATES_WITH_ZONE_ID(false), 

    Feature that determines whether time values that represents time periods
(durations, periods, ranges) are to be serialized by default using
a numeric (true) or textual (false) representations. Note that numeric
representation may mean either simple number, or an array of numbers,
depending on type.
 Note: whether Map keys are serialized as Strings or not is controlled using WRITE_DATE_KEYS_AS_TIMESTAMPS. 

Feature is enabled by default, so that period/duration are by default
serialized as timestamps.
Since: 2.5/**
     * Feature that determines whether time values that represents time periods
     * (durations, periods, ranges) are to be serialized by default using
     * a numeric (true) or textual (false) representations. Note that numeric
     * representation may mean either simple number, or an array of numbers,
     * depending on type.
     *<p>
     * Note: whether {@link java.util.Map} keys are serialized as Strings
     * or not is controlled using {@link #WRITE_DATE_KEYS_AS_TIMESTAMPS}.
     *<p>
     * Feature is enabled by default, so that period/duration are by default
     * serialized as timestamps.
     * 
     * @since 2.5
     */
    WRITE_DURATIONS_AS_TIMESTAMPS(true),
    
    Feature that determines how type char[] is serialized:
when enabled, will be serialized as an explict JSON array (with
single-character Strings as values); when disabled, defaults to
serializing them as Strings (which is more compact).

Feature is disabled by default.
/**
     * Feature that determines how type <code>char[]</code> is serialized:
     * when enabled, will be serialized as an explict JSON array (with
     * single-character Strings as values); when disabled, defaults to
     * serializing them as Strings (which is more compact).
     *<p>
     * Feature is disabled by default.
     */
    WRITE_CHAR_ARRAYS_AS_JSON_ARRAYS(false),

    Feature that determines standard serialization mechanism used for
Enum values: if enabled, return value of Enum.toString()
is used; if disabled, return value of Enum.name() is used.
 Note: this feature should usually have same value as DeserializationFeature.READ_ENUMS_USING_TO_STRING. 

Feature is disabled by default.
/**
     * Feature that determines standard serialization mechanism used for
     * Enum values: if enabled, return value of <code>Enum.toString()</code>
     * is used; if disabled, return value of <code>Enum.name()</code> is used.
     *<p>
     * Note: this feature should usually have same value
     * as {@link DeserializationFeature#READ_ENUMS_USING_TO_STRING}.
     *<p>
     * Feature is disabled by default.
     */
    WRITE_ENUMS_USING_TO_STRING(false),

    Feature that determines whethere Java Enum values are serialized
as numbers (true), or textual values (false). If textual values are
used, other settings are also considered.
If this feature is enabled,
 return value of Enum.ordinal()
(an integer) will be used as the serialization.
 Note that this feature has precedence over WRITE_ENUMS_USING_TO_STRING, which is only considered if this feature is set to false. 

Feature is disabled by default.
/**
     * Feature that determines whethere Java Enum values are serialized
     * as numbers (true), or textual values (false). If textual values are
     * used, other settings are also considered.
     * If this feature is enabled,
     *  return value of <code>Enum.ordinal()</code>
     * (an integer) will be used as the serialization.
     *<p>
     * Note that this feature has precedence over {@link #WRITE_ENUMS_USING_TO_STRING},
     * which is only considered if this feature is set to false.
     *<p>
     * Feature is disabled by default.
     */
    WRITE_ENUMS_USING_INDEX(false),

    Feature that determines whether Map entries with null values are
to be serialized (true) or not (false).
 NOTE: unlike other SerializationFeatures, this feature cannot be
dynamically changed on per-call basis, because its effect is considered during
construction of serializers and property handlers.

Feature is enabled by default.
Deprecated: Since 2.9 there are better mechanism for specifying filtering; specifically using JsonInclude or configuration overrides (see ObjectMapper.configOverride(Class<?>)})./**
     * Feature that determines whether Map entries with null values are
     * to be serialized (true) or not (false).
     *<p>
     * NOTE: unlike other {@link SerializationFeature}s, this feature <b>cannot</b> be
     * dynamically changed on per-call basis, because its effect is considered during
     * construction of serializers and property handlers.
     *<p>
     * Feature is enabled by default.
     *
     * @deprecated Since 2.9 there are better mechanism for specifying filtering; specifically
     *   using {@link com.fasterxml.jackson.annotation.JsonInclude} or configuration overrides
     *   (see {@link ObjectMapper#configOverride(Class)}}).
     */
    @Deprecated // since 2.9
    WRITE_NULL_MAP_VALUES(true),

    Feature that determines whether Container properties (POJO properties
with declared value of Collection or array; i.e. things that produce JSON
arrays) that are empty (have no elements)
will be serialized as empty JSON arrays (true), or suppressed from output (false).
 Note that this does not change behavior of Maps, or "Collection-like" types. 
 NOTE: unlike other SerializationFeatures, this feature cannot be
dynamically changed on per-call basis, because its effect is considered during
construction of serializers and property handlers.

Feature is enabled by default.
Deprecated: Since 2.8 there are better mechanism for specifying filtering; specifically using JsonInclude or configuration overrides./**
     * Feature that determines whether Container properties (POJO properties
     * with declared value of Collection or array; i.e. things that produce JSON
     * arrays) that are empty (have no elements)
     * will be serialized as empty JSON arrays (true), or suppressed from output (false).
     *<p>
     * Note that this does not change behavior of {@link java.util.Map}s, or
     * "Collection-like" types.
     *<p>
     * NOTE: unlike other {@link SerializationFeature}s, this feature <b>cannot</b> be
     * dynamically changed on per-call basis, because its effect is considered during
     * construction of serializers and property handlers.
     *<p>
     * Feature is enabled by default.
     *
     * @deprecated Since 2.8 there are better mechanism for specifying filtering; specifically
     *   using {@link com.fasterxml.jackson.annotation.JsonInclude} or configuration overrides.
     */
    @Deprecated // since 2.8
    WRITE_EMPTY_JSON_ARRAYS(true),

    Feature added for interoperability, to work with oddities of so-called "BadgerFish" convention. Feature determines handling of single element Collections and arrays: if enabled, Collections and arrays that contain exactly one element will be serialized as if that element itself was serialized. 
When enabled, a POJO with array that normally looks like this:
 { "arrayProperty" : [ 1 ] }

will instead be serialized as
 { "arrayProperty" : 1 }

 Note that this feature is counterpart to DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY (that is, usually both are enabled, or neither is). 

Feature is disabled by default, so that no special handling is done.
/**
     * Feature added for interoperability, to work with oddities of
     * so-called "BadgerFish" convention.
     * Feature determines handling of single element {@link java.util.Collection}s
     * and arrays: if enabled, {@link java.util.Collection}s and arrays that contain exactly
     * one element will be serialized as if that element itself was serialized.
     *<p>
     * When enabled, a POJO with array that normally looks like this:
     *<pre>
     *  { "arrayProperty" : [ 1 ] }
     *</pre>
     * will instead be serialized as
     *<pre>
     *  { "arrayProperty" : 1 }
     *</pre>
     *<p>
     * Note that this feature is counterpart to {@link DeserializationFeature#ACCEPT_SINGLE_VALUE_AS_ARRAY}
     * (that is, usually both are enabled, or neither is).
     *<p>
     * Feature is disabled by default, so that no special handling is done.
     */
    WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED(false),

    Feature that determines whether BigDecimal entries are serialized using BigDecimal.toPlainString() to prevent values to be written using scientific notation.  NOTE: since this feature typically requires use of JsonGenerator.writeNumber(String) it may cause compatibility problems since not all JsonGenerator implementations support such mode of output: usually only text-based formats support it. 

Feature is disabled by default.
Deprecated: Since 2.5: use Feature.WRITE_BIGDECIMAL_AS_PLAIN instead (using ObjectWriter.with(Feature))./**
     * Feature that determines whether {@link java.math.BigDecimal} entries are
     * serialized using {@link java.math.BigDecimal#toPlainString()} to prevent
     * values to be written using scientific notation.
     *<p>
     * NOTE: since this feature typically requires use of
     * {@link com.fasterxml.jackson.core.JsonGenerator#writeNumber(String)}
     * it may cause compatibility problems since not all {@link com.fasterxml.jackson.core.JsonGenerator}
     * implementations support such mode of output: usually only text-based formats
     * support it.
     *<p>
     * Feature is disabled by default.
     * 
     * @deprecated Since 2.5: use {@link com.fasterxml.jackson.core.JsonGenerator.Feature#WRITE_BIGDECIMAL_AS_PLAIN} instead
     *    (using {@link ObjectWriter#with(com.fasterxml.jackson.core.JsonGenerator.Feature)}).
     */
    @Deprecated // since 2.5
    WRITE_BIGDECIMAL_AS_PLAIN(false),

    Feature that controls whether numeric timestamp values are
to be written using nanosecond timestamps (enabled) or not (disabled);
if and only if datatype supports such resolution.
Only newer datatypes (such as Java8 Date/Time) support such resolution --
older types (pre-Java8 java.util.Date etc) and Joda do not --
and this setting has no effect on such types.
 If disabled, standard millisecond timestamps are assumed. This is the counterpart to WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS. 

Feature is enabled by default, to support most accurate time values possible.
Since: 2.2/**
     * Feature that controls whether numeric timestamp values are
     * to be written using nanosecond timestamps (enabled) or not (disabled);
     * <b>if and only if</b> datatype supports such resolution.
     * Only newer datatypes (such as Java8 Date/Time) support such resolution --
     * older types (pre-Java8 <b>java.util.Date</b> etc) and Joda do not --
     * and this setting <b>has no effect</b> on such types.
     *<p>
     * If disabled, standard millisecond timestamps are assumed.
     * This is the counterpart to {@link SerializationFeature#WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS}.
     *<p>
     * Feature is enabled by default, to support most accurate time values possible.
     *
     * @since 2.2
     */
    WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS(true),

    Feature that determines whether Map entries are first sorted by key before serialization or not: if enabled, additional sorting step is performed if necessary (not necessary for SortedMaps), if disabled, no additional sorting is needed. 
Feature is disabled by default.
/**
     * Feature that determines whether {@link java.util.Map} entries are first
     * sorted by key before serialization or not: if enabled, additional sorting
     * step is performed if necessary (not necessary for {@link java.util.SortedMap}s),
     * if disabled, no additional sorting is needed.
     *<p>
     * Feature is disabled by default.
     */
    ORDER_MAP_ENTRIES_BY_KEYS(false),

    /*
    /******************************************************
    /* Other
    /******************************************************
     */

    Feature that determines whether ObjectWriter should try to eagerly fetch necessary JsonSerializer when possible. This improves performance in cases where similarly configured ObjectWriter instance is used multiple times; and should not significantly affect single-use cases. 
Note that there should not be any need to normally disable this
feature: only consider that if there are actual perceived problems.

Feature is enabled by default.
Since: 2.1/**
     * Feature that determines whether {@link ObjectWriter} should
     * try to eagerly fetch necessary {@link JsonSerializer} when
     * possible. This improves performance in cases where similarly
     * configured {@link ObjectWriter} instance is used multiple
     * times; and should not significantly affect single-use cases.
     *<p>
     * Note that there should not be any need to normally disable this
     * feature: only consider that if there are actual perceived problems.
     *<p>
     * Feature is enabled by default.
     *
     * @since 2.1
     */
    EAGER_SERIALIZER_FETCH(true),

    Feature that determines whether Object Identity is compared using
true JVM-level identity of Object (false); or, equals() method.
Latter is sometimes useful when dealing with Database-bound objects with
ORM libraries (like Hibernate). Note that Object itself is actually compared,
and NOT Object Id; naming of this feature is somewhat confusing, so it is important
that Object for which identity is to be preserved are considered equal,
above and beyond ids (which are always compared using equality anyway).
 NOTE: due to the way functionality is implemented, it is very important that in addition to overriding Object.equals for Objects to match (to be considered "same") it is also necessary to ensure that Object.hashCode() is overridden to produce the exact same value for equal instances. 

Feature is disabled by default; meaning that strict identity is used, not
equals()
Since: 2.3/**
     * Feature that determines whether Object Identity is compared using
     * true JVM-level identity of Object (false); or, <code>equals()</code> method.
     * Latter is sometimes useful when dealing with Database-bound objects with
     * ORM libraries (like Hibernate). Note that Object itself is actually compared,
     * and NOT Object Id; naming of this feature is somewhat confusing, so it is important
     * that Object <b>for which identity is to be preserved</b> are considered equal,
     * above and beyond ids (which are always compared using equality anyway).
     *<p>
     * NOTE: due to the way functionality is implemented, it is very important that
     * in addition to overriding {@link Object#equals} for Objects to match (to be considered
     * "same") it is also necessary to ensure that {@link Object#hashCode()} is overridden
     * to produce the exact same value for equal instances.
     *<p>
     * Feature is disabled by default; meaning that strict identity is used, not
     * <code>equals()</code>
     *
     * @since 2.3
     */
    USE_EQUALITY_FOR_OBJECT_ID(false)
    ;

    private final boolean _defaultState;
    private final int _mask;
    
    private SerializationFeature(boolean defaultState) {
        _defaultState = defaultState;
        _mask = (1 << ordinal());
    }

    @Override
    public boolean enabledByDefault() { return _defaultState; }


    @Override
    public int getMask() { return _mask; }

    @Override
    public boolean enabledIn(int flags) { return (flags & _mask) != 0; }
}
/

com.fasterxml.jackson.core/ jackson-databind/ 2.9.5/ com/fasterxml/jackson/databind/SerializationFeature.java
