Jackson Version 2.12 was released on November 28, 2020: two release candidates (2.12.0-rc1, 2.12.0-rc2) were released prior to the final 2.12.0.

This wiki page gives a list of links to all changes (with brief descriptions) included.

Aside from detailed change notes below, there is a separate 2.12 Acknowledgements page for special thanks.

Branch is nominally open but it is not likely that there will be full patch releases beyond (2.12.7). Micro-patches are possible.

• 2.12.1 (08-Jan-2021)
• 2.12.2 (03-Mar-2021)
• 2.12.3 (12-Apr-2021)
• 2.12.4 (06-Jul-2021)
• 2.12.5 (27-Aug-2021)
• 2.12.6 (15-Dec-2021)
• 2.12.7 (26-May-2022)

Following micro-patches have been released:

• jackson-databind 2.12.6.1 (26-Mar-2022) -- with jackson-bom version 2.12.6.20220326
  • #2816: Optimize UntypedObjectDeserializer wrt recursion (CVE-2020-36518)
• jackson-databind 2.12.7.1 (12-Oct-2022) -- with jackson-bom version 2.12.7.20221012
  • #3582: Add check in BeanDeserializer._deserializeFromArray() to prevent use of deeply nested arrays [CVE-2022-42004]
  • #3590: Add check in primitive value deserializers to avoid deep wrapper array nesting wrt UNWRAP_SINGLE_VALUE_ARRAYS [CVE-2022-42003]

• Jackson 2.12 features (Overview)
  • Jackson 2.12: Deduction-based Polymorphism
  • Jackson 2.12: @JsonIncludeProperties
  • Jackson 2.12: ConstructorDetector
  • Jackson 2.12: CoercionConfig system
  • Jackson 2.12: Support java.lang.Record
• Jackson 2.12: Improved XML handling

JDK baseline for use since 2.11 is retained with following exceptions:

1. Ion dataformat module (part of jackson-dataformats-binary) now requires Java 8 due to new optional IonJavaTimeModule
2. Eclise-collections datatype module (part of jackson-datatypes-collections) requires Java 8 (was the case before but not documented)
3. Guava datatype module (part of jackson-datatypes-collections) requires Java 8 due to Guava 21 dependency upgrades baseline

JDK 8 is required to build all components, however, as module info inclusion plug-in requires it (note: publishing to Maven Central also requires JDK 8), but the minimum runtime version is JDK/JVM 7, with following exceptions:

• jackson-annotations, jackson-core, jackson-jr only require JDK/JVM 6
• JDK/JVM 8 higher needed for:
  • Kotlin and Scala language modules
  • Java 8 modules (datatypes, parameter-names, jsr310 date/time)
  • Ion dataformat module
  • Eclipse-collections datatype module

Due to use of java.util.Objects, part of JDK 7, minimum Android version supported appears to be 4.4 / API Level 19:

https://developer.android.com/reference/kotlin/java/util/Objects

Jackson Kotlin module is now compiled against (and is designed to work with) Kotlin 1.4.

Support for Scala 2.10 is dropped (so that Jackson 2.11 is the last version of with Scala 2.10 support): Jackson 2.12 will support following Scala versions:

• 2.11
• 2.12
• 2.13

Addition of explicit support for java.lang.Record changes handling slightly for one specific case: if you have a Record type with 1 property, like:

public record MyValueRecord(String value) {}

it would be assumed to use "Delegating" style of parameter passing, and would (only) accept JSON String to bind. With 2.12 all Records default to "Properties" style binding so a single-property JSON Object is expected instead. Note that it is possible to annotate constructor explicitly:

public record MyValueRecord(String value) {
    @JsonCreator(mode = JsonCreator.Mode.DELEGATING)
    public MyValueRecord(String value) {
        this.value = value;
    }
}

to produce pre-2.12 behavior, as necessary. See jackson-databind#2980 for details.

Default for FromXmlParser.Feature.EMPTY_ELEMENT_AS_NULL changed from true (2.9 - 2.11) to false, so that no automatic coercion done from empty elements like <empty/> into null

• see jackson-dataformat-xml#411

It also looks like handling of "empty values" (zero-length String) for scalar values like numbers changed, as per jackson-dataformat-xml#473, but this issue should be resolved in 2.12.4.

• Input null value will be deserialized as JsonValue.NULL
  • see datatypes-misc#2

• New Base module -- jackson-datatype-blackbird
  • (Future) Replacement for Afterburner module: solves same use case, speeding up of POJO databind
  • Works better than Afterbuern with newer JVMs (Java 9 and later)
  • Contributed by Steven Schlansker (@stevenschlansker)
• Alternate jars with jakarta classifier for modules that rely on JAX-xxx APIs, to support new "Jakarta" namespaced apis:
  • JAX-RS modules (jackson-jaxrs-XXX-provider) and JAXB annotations module (jackson-module-jaxb-annotations) have both "regular" jar and variant with classifier of jakarta
  • Existing ("old") jars rely on 2.x version of JAX-WS, JAX-RS APIs, in existing javax. namespace
  • New "jakarta" variants (with classifier of jakarta) will refer to repackaged "Jakarta" variants of APIs
  • Users will need to specify classifier, for now, if they want/need to use newer dependencies

#2113 adds CoercionConfig system which allows indicating which of 4 CoercionActions to take for given input shape, target type:

• Fail: not allowed, throw exception
• AsNull: allow, coerce to null (although may be further mapped via other mechanisms)
• AsEmpty: allow, coerce to "empty" value of type (empty Collection, POJO with no properties set)
• TryConvert: allow if there is logical conversion (for example String "123" can be parsed, converted to int value 123)

Input shapes are defined with CoercionInputShape enum which roughly corresponds to JsonToken values, but also has 3 logical types for "empty" String, Array and Object as special cases.

Target type is specific both by concrete (specific type), Class and new LogicalType that has a smaller set of values.

Rules can be targeted at 3 levels:

1. For specific concrete type (Class), input shape
2. For logical type (like LogicalType.Boolean) -- covers boolean, Boolean, elements in boolean[], AtomicBoolean -- and input shape
3. Default action for coercions from input shape, used if no per-type (concrete or logical) specified -- most commonly used for input shape of EmptyString

This feature allows defining coercion rules like:

• Let empty String value become POJO similar to being deserialized from { } JSON Input (especially useful for XML)
• Let empty String value become null for specified type(s)
• Prevent coercion from JSON Numbers into Java booleans (by default non-zero JSON Integers map to Boolean values as true)

This is issue databind#1296: explained in bit more detail on Jackson 2.12: @JsonIncludeProperties blog post

• Support for "Arrays" with Tree Model, JsonNode, "untyped"/List/Map (nominal java.lang.Object)
  • dataformat-xml#205: XmlMapper/UntypedObjectDeserializer swallows duplicated elements in
  • dataformat-xml#403: Make JsonNode implicitly create ArrayNodes for repeated XML Elements (aka "Make JsonNode work with XML")
• Basic support for "Mixed Content" (element(s) AND text for given XML element)
  • dataformat-xml#405: Mixed content not exposed through FromXmlParser, lost by JsonNode
  • As with array support, usable via JsonNode and "untyped" (Map/List/Object)
  • Does not retain full ordering so further work needed for 100% high fidelity mapping
• Fully support root values, including scalar types
  • dataformat-xml#121: XmlMapper not deserializing root-level Enums
  • dataformat-xml#254: No String-argument constructor/factory method to deserialize from String value when it is a Integer
  • dataformat-xml#412: Coercion from element-with-attribute-and-text only works for String, not other scalar types
• Support deserialization of scalars even for elements that contain additional attributes

Pretty much as expected, see https://github.com/FasterXML/jackson-databind/issues/2709 for details: reading and writing of java.lang.Record should work when running on Java 14 or later, using expected accessors, constructors, and annotation overrides (if any).

The oldest open issue, databind#43 is now implemented. It basically allows omitting of actual Type Id field or value, as long as the subtype can be deduced (@JsonTypeInfo(use=DEDUCTION)) from existence of fields. That is, every subtype has a distinct set of fields they included, and so during deserialization type can be uniquely and reliably detected.

See Jackson 2.12: Deduction-based Polymorphism for longer explanation.

Issue databind#1498 addresses one remaining case where Creator (constructor) auto-detection was not possible: that of single-argument Constructors (due to ambiguity between Properties-based and Delegating choices). 2.12 allows configuration of ContructorDetector to resolve this aspect.

See Jackson 2.12: ConstructorDetector for longer explanation.

• dataformats-binary#213: There is new optional IonJavaTimeModule that allows use of native Ion datatypes with Java 8 Date/Time types (JSR-310)

• JsonNodeFeature/-Config JSTEP-3: configuring reading/writing of JsonNode
• @PreSerialize / @PostDeserialize method annotations (https://github.com/FasterXML/jackson-databind/issues/2045)
• Other format module fixes:
  • Protobuf: proto3, use of Wire/schema for protoc parsing
  • CSV, structured?
  • Logical types: Avro, CBOR

• #171: JsonSubType.Type should accept array of names
• #173: Jackson version alignment with Gradle 6
• #174: Add @JsonIncludeProperties
• #175: Add @JsonTypeInfo(use=DEDUCTION)
• #177: Ability to use @JsonAnyGetter on fields
• #179: Add @JsonKey annotation
• #180: Allow repeated calls to SimpleObjectIdResolver.bindItem() for same mapping
• #181: Add namespace property for @JsonProperty (for XML module)

• #500: Allow "optional-padding" for Base64Variant
• #573: More customizable TokenFilter inclusion (using Tokenfilter.Inclusion)
• #618: Publish Gradle Module Metadata
• #619: Add StreamReadCapability for further format-based/format-agnostic handling improvements
• #627: Add JsonParser.isExpectedNumberIntToken() convenience method
• #630: Add StreamWriteCapability for further format-based/format-agnostic handling improvements
• #631: Add JsonParser.getNumberValueExact() to allow precision-retaining buffering
• #639: Limit initial allocated block size by ByteArrayBuilder to max block size

• #43: Add option to resolve type from multiple existing properties, @JsonTypeInfo(use=DEDUCTION)
• #921: Deserialization Not Working Right with Generic Types and Builders
• #1296: Add @JsonIncludeProperties(propertyNames) (reverse of @JsonIgnoreProperties)
• #1458: @JsonAnyGetter should be allowed on a field
• #1498: Allow handling of single-arg constructor as property based by default
• #1852: Allow case insensitive deserialization of String value into boolean/Boolean (esp for Excel)
• #1886: Allow use of @JsonFormat(with=JsonFormat.Feature.ACCEPT_CASE_INSENSITIVE_PROPERTIES) on Class
• #1919: Abstract class included as part of known type ids for error message
• #2091: ReferenceType does not expose valid containedType
• #2113: : Add CoercionConfig[s] mechanism for configuring allowed coercions
• #2118: JsonProperty.Access.READ_ONLY does not work with "getter-as-setter" Collections
• #2215: Support BigInteger and BigDecimal creators in StdValueInstantiator
• #2283: JsonProperty.Access.READ_ONLY fails with collections when a property name is specified
• #2675: Support use of Void valued properties (MapperFeature.ALLOW_VOID_VALUED_PROPERTIES)
• #2683: Explicitly fail (de)serialization of java.time.* types in absence of registered custom (de)serializers
• #2707: Improve description included in by DeserializationContext.handleUnexpectedToken()
• #2709: Support for JDK 14 record types
• #2715: PropertyNamingStrategy class initialization depends on its subclass, this can lead to class loading deadlock
• #2719: FAIL_ON_IGNORED_PROPERTIES does not throw on READONLY properties with an explicit name
• #2726: Jackson version alignment with Gradle 6
• #2732: Allow JsonNode auto-convert into ArrayNode if duplicates found (for XML)
• #2733: Allow values of "untyped" auto-convert into List if duplicates found (for XML)
• #2775: Disabling FAIL_ON_INVALID_SUBTYPE breaks polymorphic deserialization of Enums
• #2804: Throw InvalidFormatException instead of MismatchedInputException for ACCEPT_FLOAT_AS_INT coercion failures
• #2871: Add @JsonKey annotation (similar to @JsonValue) for customizable serialization of Map keys
• #2873: MapperFeature.ACCEPT_CASE_INSENSITIVE_ENUMS should work for enum as keys
• #2879: Add support for disabling special handling of "Creator properties" wrt alphabetic property ordering
• #2885: Add JsonNode.canConvertToExactIntegral() to indicate whether floating-point/BigDecimal values could be converted to integers losslessly
• #2895: Improve static factory method generic type resolution logic
• #2909: @JsonValue not considered when evaluating inclusion
• #2910: Make some java platform modules optional
• #2925: Add support for serializing java.sql.Blob
• #2928: AnnotatedCreatorCollector should avoid processing synthetic static (factory) methods
• #2932: Problem with implicit creator name detection for constructor detection

• #222: Add CBORGenerator.Feature.LENIENT_UTF_ENCODING for lenient handling of Unicode surrogate pairs on writing
• #228: Add support for decoding unassigned "simple values" (type 7)

• #199: Empty Lists can only be String-typed in CSV
• #222: JsonParser.Feature.EMPTY_STRING_AS_NULL does not work when text is parsed as String[]

• #212: Optimize IonParser.getNumberType() using IonReader.getIntegerSize()
• #213: Add support to (de)serialize Ion timestamps to/from java.time classes

• #97: Weird Exception during read with Type info
• #121: XmlMapper not deserializing root-level Enums
• #124: Deserialization of an empty list (with empty XML tag) results in null
• #205: XmlMapper/UntypedObjectDeserializer swallows duplicated elements in XML documents
• #226: XML to JSON - IOException when parsing XML with XMLMapper
• #252: Empty (or self-closing) Element representing List is incorrectly deserialized as null, not Empty List
• #254: No String-argument constructor/factory method to deserialize from String value when it is a Integer
• #257: Deserialization fails of lists containing elements with xml:space attribute
• #262: Make ToXmlGenerator non-final
• #273: Input mismatch with case-insensitive properties
• #307: Missing collection item when they are not wrapped during unmarshal with multiple namespaces
• #314: Jackson gets confused by parent list element
• #318: XMLMapper fails to deserialize null (POJO reference) from blank tag
• #319: Empty root tag into List deserialization bug
• #360: Add a feature to support writing xsi:nil attribute for null values
• #374: Deserialization fails with XmlMapper and DeserializationFeature.UNWRAP_ROOT_VALUE
• #377: ToXmlGenerator ignores Base64Variant while serializing byte[]
• #380: Unable to deserialize root-level Instant value from XML
• #390: Unexpected attribute at string fields causes extra objects to be created in parent list
• #397: XmlReadContext does not keep track of array index
• #403: Make JsonNode implicitly create ArrayNodes for repeated XML Elements
• #405: Mixed content not exposed through FromXmlParser, lost by JsonNode
• #411: Change default setting of FromXmlParser.Feature.EMPTY_ELEMENT_AS_NULL from true to false
• #412: Coercion from element-with-attribute-and-text only works for String not other scalar types
• #422: Elements containing parsed incorrectly when at the end of another element
• #434: Add missing ElementType.ANNOTATION_TYPE for Jackson xml annotations to allow bundling
• Add Gradle Module Metadata (https://blog.gradle.org/alignment-with-gradle-module-metadata)
• Upgrade Woodstox dependency to 6.2.3 (<- 6.2.1)

• #71: Hex number as an entry of an Object causing problem(s) with binding to POJO
• #130: Empty String deserialized as null instead of empty string
• #175: Add YAMLGenerator.Feature.INDENT_ARRAYS_WITH_INDICATOR to indent by 2 spaces
• #226: Quote 'y'/'Y'/'n'/'N' as names too (to avoid problems with Boolean keys)
• #229: Allow configuring the way "must quote" is determined for property names, String values
• #231: Typed object with anchor throws Already had POJO for id (note: actual fix in jackson-annotations)
• #232: Typed object throws "Missing type id" when annotated with '@JsonIdentityInfo'
• #233: Support decoding Binary, Octal and Hex numbers as integers

• #25: (guava) SetMultimap should be deserialized to a LinkedHashMultimap by default
• #79: (guava) Guava's RangeHelper causing NPE in PropertyNamingStrategy
• (guava) Update "preferred" Guava version to 21.0
• (guava) Require Java 8 due to Guava 21 baseline (JRE variant)

• #136: Add feature WRAP_IDENTIFIER_IN_OBJECT to allow disabling of wrapping of "id" attribute

• #94: Deserialization of timestamps with UTC timezone to LocalDateTime doesn't yield correct time
• #165: Problem in serializing negative Duration values
• #166: Cannot deserialize OffsetDateTime.MIN or OffsetDateTime.MAX with ADJUST_DATES_TO_CONTEXT_TIME_ZONE enabled
• #175: ObjectMapper#setTimeZone ignored by jsr-310/datetime types during serialization when using @JsonFormat annotation
• #184: DurationDeserializer should use @JsonFormat.pattern (and config override) to support configurable ChronoUnit
• #189: Support use of "pattern" (ChronoUnit) for DurationSerializer too

• #116: Improve schema support for DateTimeZone type
• #117: Timestamp deserialization not working for CSV, Properties or XML

• #117: Use of ToStringSerializer via @JsonSerialize on int/long property does not work
• #118: Using @JsonFormat(shape = JsonFormat.Shape.STRING) on int, long properties not working

• #115: Remove java.beans.Introspector dependency from JAXB module (to get rid of java.desktop module dep)
• #116: Jakarta Namespace Support
  • See notes earlier on "Jakarta" variants of module jars: users will need to opt-in by using Maven classifier jakarta for version with "new" JAX-WS/JAXB dependencies

• #100: Prevent "double-prefixing" Mr Bean generated classes

• #322: Added extension methods to SimpleModule addSerializer and addDeserializer to support KClass arguments that register the serializer/deserializer for both the java type and java class.
• #356: Kotlin 1.4 support
• #385: Add Moditect, source module info, to allow Kotlin module usage with Java Module system

• Add Gradle Module Metadata (https://blog.gradle.org/alignment-with-gradle-module-metadata)

• #370: Support jackson feature @JsonMerge
• #449: Remove jackson-module-paranamer dependency. Scala 2.11 variant uses Paranamer directly still but Scala 2.12 and 2.13 releases no longer use Paranamer.
• #455: get ScalaAnnotationIntrospector to ignore non-Scala classes
• #462: Unable to deserialize Seq or Map with AS_EMPTY null handling
• #466: Add support for WRITE_SINGLE_ELEM_ARRAYS_UNWRAPPED
• #467: Serializer for Scala Iterable/Iterator converts to Java Collection - avoid this conversion
• #480: Drop Scala 2.10 support

• #127: Allow multiple implementations of JAX-RS for all providers
• #128: Module-Info Enhancements - JAX-RS updates for Jakarta Release version