/jackson

Main Portal page for Jackson project

Jackson Project Home @github

This will be the portal page for Jackson Project. Jackson is a suite of data-processing tools for Java (and JVM platform), including the flagship JSON parsing and generation library, as well as additional modules to process data encoded in Avro, CBOR, CSV, Smile, XML or YAML (and list of supported format is still growing -- see additional experimental/external projects listed below!)

Portal shall contain links to all active Jackson projects owned by Jackson project team; as well as additional links to external resources.

Actively developed versions

Jackson suite has two major branches: 1.x is in maintenance mode, and only bug-fix versions are released; 2.x is the actively developed version. Versions use different Java packages and Maven artifact ids, so they are not mutually compatible, but can peacefully co-exist: a project can depend on both Jackson 1.x and 2.x, without conflicts. This is by design.

The latest stable versions from these branches are:

  • 2.4.4, released 25-Nov-2014
  • [1.9.13], released 14-Jul-2013

Recommended way to use Jackson is via Maven; releases are made to Central Maven Repository (CMR). Individual project pages typically contain download links, leading to CMR.

Release notes found from Jackson Releases page.

Active Jackson projects

Most projects listed below are lead by Jackson development team; but some by other at-large Jackson community members. We try to keep versioning of modules compatible to reduce confusion regarding which versions work together.

Core modules

Core modules are the foundation on which extensions (modules) build upon. These are three and they are known as:

  • Streaming (docs) ("jackson-core") defines low-level streaming API, and includes JSON-specific implementations
  • Annotations (docs) ("jackson-annotations") contains standard Jackson annotations
  • Databind (docs) ("jackson-databind") implements data-binding (and object serialization) support on streaming package; it depends both on streaming and annotations packages

Third-party datatype modules

These extensions are plug-in Jackson Modules (registered with ObjectMapper.registerModule()), and add support for datatypes of various commonly used Java libraries, by adding serializers and deserializers so that Jackson databind package (ObjectMapper / ObjectReader / ObjectWriter) can read and write these types.

  • Guava: support for many of Guava datatypes.
  • Hibernate: support for Hibernate features (lazy-loading, proxies)
  • HPPC: support for High-Performance Primitive Containers containers
  • Joda: support for types of Joda date/time library datatypes
  • JDK7: support for JDK 7 data types not included in previous versions
  • JDK8: support for JDK 8 data types not included in previous versions, including Optional (but excluding new Date types which are in JSR-310 module above)
  • JSR-310: support for "Java 8 Dates" (ones added in JDK 8)
    • Also, for pre-Java8 users can use "ThreeTen" module for backport on Java7
  • JSR-353: support for "Java JSON API" types (specifically, its tree model objects)
  • org.json: support for "org.json JSON lib" types like JSONObject, JSONArray
  • Yandex Bolts support for reading/writing types defined by Yandex Bolts collection types (Functional Programming inspired immutable collections)

Providers for JAX-RS

Jackson JAX-RS Providers has handlers to add dataformat support for JAX-RS implementations (like Jersey, RESTeasy, CXF). Providers implement MessageBodyReader and MessageBodyWriter. Supported formats currently include JSON, Smile, XML and CBOR.

Data format modules

Data format modules offer support for data formats other than JSON. Most of them simply implement streaming API abstractions, so that databinding component can be used as is; some offer (and few require) additional databind level functionality for handling things like schemas.

Currently following data format modules are fully usable and supported:

  • Avro: supports Avro data format, with streaming implementation plus additional databind-level support for Avro Schemas
  • CBOR: supports CBOR data format (a binary JSON variant).
  • CSV: supports Comma-separated values format -- streaming api, with optional convenience databind additions
  • Smile: supports Smile (binary JSON) -- 100% API/logical model compatible via streaming API, no changes for databind
  • XML: supports XML; provides both streaming and databind implementations. Similar to JAXB' "code-first" mode (no support for "XML Schema first", but can use JAXB beans)
  • YAML: supports YAML, which being similar to JSON is fully supported with simple streaming implementation

There are also other data format modules, provided by developers outside Jackson core team:

  • bson4jackson: adds support for BSON data format (by Mongo project).
    • Implemented as full streaming implementation, which allows full access (streaming, data-binding, tree-model)
    • Also see [MongoJack] library below; while not a dataformat module, it allows access to BDON data as well.
  • MessagePack: adds MessagePack (aka MsgPack) support
    • Implemented as full streaming implementation, which allows full access (streaming, data-binding, tree-model)
  • HOCON: experimental, partial implementation to support HOCON format -- work in progress

JVM Language modules

  • Kotlin to handle native types of Kotlin (NOTE: 2.4.3 the first official release)
  • Scala to handle native Scala types (including but not limited to Scala collection/map types, case classes)

Support for Schemas

Jackson annotations define intended properties and expected handling for POJOs, and in addition to Jackson itself using this for reading/writing JSON and other formats, it also allows generation of external schemas. Some of this functionality is included in above-mentioned data-format extensions; but there are also many stand-alone Schema tools, such as:

Other modules, stable

Other fully usable modules by FasterXML team include:

  • Afterburner: speed up databinding by 30-40% with bytecode generation to replace use of Reflection
  • JAXB Annotations: allow use of JAXB annotations as an alternative (in addition to or instead of) standard Jackson annotations
  • Mr Bean: "type materialization" -- let Mr Bean generate implementation classes on-the-fly (NO source code generation), to avoid monkey code
  • Paranamer: tiny extension for automatically figuring out creator (constructor, factory method) parameter names, to avoid having to specify @JsonProperty.

Other modules, experimental

And finally, there are other still experimental modules provided by FasterXML team

  • Guice: extension that allows injection values from Guice injectors (and basic Guice annotations), instead of standard @JacksonInject (or in addition to)
    • note: as of 2.2.x, this is in proof-of-concept stage; should become stable for 2.3
  • JDK 8 Parameter names: Module that adds support for using a new JDK8 feature: ability to access names of constructor and method parameters.

Jackson jr

While Jackson databind is a good choice for general-purpose data-binding, its footprint and startup overhead may be problematic in some domains, such as mobile phones; and especially for light usage (couple of reads or writes). In addition, some developers find full Jackson API overwhelming.

For all these reasons, we decided to create a much simpler, smaller library, which supports a subset of functionality, called Jackson jr. It builds on Jackson Streaming API, but does not depend on databind. As a result its size (both jar, and runtime memory usage) is considerably smaller; and its API is very compact.

Third-party non-module libraries based on Jackson

Documentation

Web sites

  • jackson-docs is our Github Jackson documentation hub
  • Jackson Wiki contains older documentation (some 1.x specific; but mostly relevant for both 1.x and 2.x)
  • CowTalk -- Blog with lots of Jackson-specific content
  • Jackson Users is a Jackson-specific discussion forum

Note on reporting Bugs

Jackson bugs need to be reported against component they affect: for this reason, issue tracker is not enabled for this project. If you are unsure which specific project issue affects, the most likely component is jackson-databind, so you would use Jackson Databind Issue Tracker.

Paperwork

  • Jackson Contributor License Agreement (CLA) is a one-page document we need from every contributor of code (we will request it for pull requests)

Older resources

These are obsolete resources, mostly useful for historical interest: