Jackson Release 2.7

Tatu Saloranta edited this page Nov 23, 2018 · 77 revisions

Version 2.7 development started in August 2015; and the first official release happened on January 10, 2016.

New Modules, status changes

  • New datatype module: jackson-datatype-pcollections
  • Kotlin module become official with 2.7.2, as that is the first version based on the official Kotlin 1.0
  • jackson-module-jdk7 was deprecated: all functionality was dynamically added directly in jackson-databind, as explained below.
    • no 2.7.x version was released (in retrospect, a no-op version might have made more sense)


Beyond initial 2.7.0 (described here), following patch releases have been made:

At this point branch is not open any more (that is, no more full patch releases are planned).

Following micro-patches have been released:

  • jackson-databind
    • (18-Apr-2017)
      • #1599: Jackson Deserializer security vulnerability
      • Minor robustification of method resolution in AnnotatedClass
    • (20-Dec-2017)
      • #1607: @JsonIdentityReference not used when setup on class only
      • #1628: Don't print to error stream about failure to load JDK 7 types
      • #1680: Blacklist couple more types for deserialization
      • #1737: Block more JDK types from polymorphic deserialization
      • #1855: Blacklist for more serialization gadgets (dbcp/tomcat, spring)
    • (11-Feb-2018)
      • #1872: NullPointerException in SubTypeValidator.validateSubType when validating Spring interface
      • #1931: Two more c3p0 gadgets to exploit default typing issue
    • (08-Jun-2018)
      • #2032: CVE-2018-11307: Potential information exfiltration with default typing, serialization gadget from MyBatis
      • #2052: CVE-2018-12022: Block polymorphic deserialization of types from Jodd-db library
      • #2058: CVE-2018-12023: Block polymorphic deserialization of types from Oracle JDBC driver
    • (23-Nov-2018)
      • #1899: Another two gadgets to exploit default typing issue in jackson-databind
      • #2097: Block more classes from polymorphic deserialization (CVE-2018-14718 - CVE-2018-14721)
      • #2186: Block more classes from polymorphic deserialization (CVE-2018-19360, CVE-2018-19361, CVE-2018-19362)
  • jackson-module-kotlin (10-Feb-2018)
    • Upgrade to work Kotlin 1.2(.21)

Changes: compatibility

Starting with 2.7, JDK baseline will be Java 7 / JDK 7, with following exceptions:

  • jackson-annotations and jackson-core (streaming) will remain Java 6
  • No new language features are yet used (diamond pattern, try-with-resources); only JDK types
  • All JDK 7 types are accessed dynamically
    • Deserializer for java.nio.file.Path
    • Handling of new annotations under java.beans: @ConstructorProperties, @Transient via JacksonAnnotationIntrospector, but

So it should still be possible to use Jackson 2.7 on Java 6, but not compile, build. With Jackson 2.8, Java 7 languages features will be allowed

Other compatibility changes:

  • ObjectMapper default timezone now UTC, not GMT (as with 2.6 and prior): usually the two behave the same, but may cause minor variation in serialized form
  • As per #952 (see below), behavior of JsonInclude.Include.NON_EMPTY will be reverted to 2.5 level: it only applies to Collections, Maps, arrays and Strings: default scalar values (like 0 for int) will NOT be considered "empty".
    • Behavior of NON_EMPTY was different only for 2.6: prior to that behavior was the same as with 2.7 and onwards

Implemented major features

Add support for dataformat-specific features

With Jackson 2.6, ObjectReader allows passing of JsonParser.Feature overrides, and ObjectWriter similarly JsonGenerator.Feature overrides. But there are some format-specific features for formats like CSV which were not being passed before 2.7.

Since ObjectReader and ObjectWriter are not easy to sub-class (an attempt to do so pointed out a few inconvenient quirks Java typing would impose), it would be most convenient to be able to pass opaque bitflags to actual parser/generator implementation, and this is what has been added.

Fix (generic) type resolution mechanism

While Jackson has the best support for generic types of all Java JSON libraries, there are certain tricky edge cases that do not work. Specifically, type variable aliasing (case where variable name like T binds to different types at different points in hierarchy) is not correctly resolved, as variable binding is constructed globally and not hierarchically.

java-classmate library which was built based on my experiences with Jackson does handle all these cases correctly (to my knowledge), and could be used as a blueprint for improved system. It can not necessarily be used directly because Jackson's type system is more complicated and adds semantics that classmate does not use (like Map and Collection types being special), but should help as an example.

Revert back expansion of NON_EMPTY handling

Although the intent has always been that Include.NON_EMPTY would apply not just to empty arrays, Collections , Maps and Strings, to include things like numbers with default values (0 for int, for example). But since many JsonSerializers did NOT properly check for these conditions, before Jackson 2.6 NON_EMPTY exclusion did not work as extensively as intended, and many users came to depend on this specific behavior.

With 2.6 serializers were improved to handle "emptiness" as originally envisioned. This confused some of users, leading to confusion and frustration on what seemed like arbitrary changes.

After lengthy discussions over this issue, it seems that instead of using extended definition of what is empty, it makes more sense to use another value, NON_DEFAULT for such concept, and keep NON_EMPTY to strictly ONLY exclude:

  • Anything that is null (that is, a superset of NON_NULL)
  • Anything that is "absent" (for Optionals and other "Reference Types" -- superset of NON_ABSENT)
  • Empty container types with no elements:
    • java.util.Collection
    • java.util.Map
    • Java arrays
  • Empty Strings

With that, NON_DEFAULT will have two modes:

  • When applied on containing class, it will try to compare actual defaults values of the POJO for given properties
  • Otherwise (when NON_DEFAULT is either default global or per-type value; or used as per-property override), use per-type criteria, where:
    • anything that would be considered "empty" is excluded, but also
    • default values for primitives (like 0 for int) and their wrappers (Integer.valueOf(0) for Integer) are also excluded

Changes, core


  • #37: Add @JsonClassDescription
  • #77: Add a new ObjectIdGenerator, StringIdGenerator, to allow arbitrary String Object Id usage
  • Major rewrite of merging of JsonFormat.Value and JsonInclude.Value, to allow for better multi-level defaults (global, per-type, property)


  • #37: JsonParser.getTokenLocation() doesn't update after field names
  • #198: Add back-references to JsonParser / JsonGenerator for low-level parsing issues (via JsonParseException, JsonGenerationException)
  • #211: Fix typo of function name com.fasterxml.jackson.core.Version.isUknownVersion() (add isUnknownVersion(), deprecated misspelled variant)
  • #229: Array element and field token spans include previous comma.


  • 76: Problem handling datatypes Recursive type parameters
  • 432: StdValueInstantiator unwraps exceptions, losing context
  • 497: Add new JsonInclude.Include feature to exclude maps after exclusion removes all elements
  • 803: Allow use of StdDateFormat.setLenient()
  • 819: Add support for setting FormatFeature via ObjectReader, ObjectWriter
  • 857: Add support for java.beans.Transient
  • 905: Add support for @ConstructorProperties
  • 915: ObjectMapper default timezone is GMT, should be UTC
  • 924: SequenceWriter.writeAll() could accept Iterable
  • 948: Support leap seconds, any number of millisecond digits for ISO-8601 Dates.
  • 952: Revert non-empty handling of primitive numbers wrt NON_EMPTY; make NON_DEFAULT use extended criteria
  • 957: Merge datatype-jdk7 stuff in (java.nio.file.Path handling)
  • 959: Schema generation: consider active view, discard non-included properties
  • 963: Add PropertyNameStrategy KEBAB_CASE
  • 978: ObjectMapper#canSerialize(Object.class) returns false even though FAIL_ON_EMPTY_BEANS is disabled
  • 998: Allow use of NON_DEFAULT for POJOs without default constructor
  • 1000: Add new mapping exception type for enums and UUIDs
  • 1010: Support for array delegator
  • 1043: @JsonFormat(with = JsonFormat.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY) does not work on fields
  • 1044: Add AnnotationIntrospector.resolveSetterConflict(...) to allow custom setter conflict resolution

Changes, Data formats


  • #21: Add AVRO_BUFFERING feature for AvroParser, AvroGenerator (enabled by default, same as existing pre-2.7 behavior)


  • #81: Add alternative way to configure 'wrap-as-array', as CsvParser feature
  • #89: Allow choice of using header-line declaration to reorder columns of explicit schema, with CsvSchema.setReorderColumns
  • #92: Allow multi-character separator values
  • #94: Change schema/mapping related JsonParseExceptions to proper JsonMappingExceptions
  • #95: Add CsvParser.Feature.IGNORE_TRAILING_UNMAPPABLE to allow skipping of all extra, unmappable columns
  • #97: Verify CSV headers are in the order as expected (added strictHeaders property in CsvSchema)
  • #103: JsonGenerator.Feature.IGNORE_UNKNOWN does not prevent error when writing structured values
  • #106: Null fields are always ignored when serializing list of
  • #109: Allow specifying (via CsvSchema) a way to map "extra" columns into specific key (to use via any setter)


  • #11: dd Support for Generating Protobuf Schema From POJO Definition


  • #156: Add XmlMapper.setDefaultUseWrapper() for convenience.
  • #167: Exception on deserializing empty element with an xsi attribute
  • #169: Fail to deserialize "empty" polymorphic classes
  • #180: Problem with deserialization of nested non-wrapped lists, with empty inner list


  • 38: Add MINIMIZE_QUOTES generator feature
  • 50: Lack of SnakeYAML Resolver leaves some missing features

Changes, Datatypes


  • #79: New configuration for Guava Range default bound type.

Java8 Date/time

  • #54: LocalDateTimeSerializer default constructor should use the same formatter as LocalDateTimeDeserializer

Changes, JAX-RS

Changes, other modules

JAXB Annotations

  • #52: Add a feature in JaxbAnnotationIntrospector to define meaning of nillable=false as "JsonInclude.NON_EMPTY"

JSON Schema

  • #80: Support NumberFormat#multipleOf
  • #81: Deserialize ArrayItems and JsonValueFormat correctly

Changes, Jackson-jr

  • #28: Remove misspelled JSON.Feature.USE_IS_SETTERS
  • #29: Add JSON.Feature.WRITE_DATES_AS_TIMESTAMP, enabling of which allows serialization of java.util.Date as long
  • #30: Add initial version of jackson-jr - based Retrofit2 Converter
  • #31: Fix failure writing UUID, URL and URI
  • #34: Add basic read-only (immutable) tree model impementation (stree)
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