Add-on module for Jackson (https://github.com/FasterXML/jackson) to support Scala-specific datatypes
Jackson is a fast JSON processor for Java that supports three models: streaming, node, and object mapping (akin to the three independent models SAX/[Stax], DOM and JAXB for XML processing).
The object mapping model is a high-level processing model that allows the user to project JSON data onto a domain-specific data model appropriate for their application, without having to deal with the low-level mechanics of JSON parsing. It is the standard object mapping parser implementaton in Jersey, the reference implementation for JSR-311 (Java API for Restful Web Services).
Scala is a functional programming language for the JVM that supports Java interoperability. Its standard library is quite distinct from Java, and does not fulfill the expectations of Jacksons default mappings. Notably, Scala collections do not derive from
java.util.Collectionor its subclasses, and Scala properties do not (by default) look like
Java Beanproperties.
The Scala Module supports serialization and limited deserialization of Scala Case Classes,
Sequences,
Maps,
Tuples,
Options, and Enumerations.
To use the Scala Module in Jackson, simply register it with the ObjectMapper instance:
// With 2.10 and later val mapper = JsonMapper.builder() .addModule(DefaultScalaModule) .build()// versions before 2.10 (also support for later 2.x but not 3.0) val mapper = new ObjectMapper() mapper.registerModule(DefaultScalaModule)
DefaultScalaModuleis a Scala object that includes support for all currently supported Scala data types. If only partial support is desired, the component traits can be included individually:
val module = new OptionModule with TupleModule {} val mapper = JsonMapper.builder() .addModule(module) .build()
You can also mixin
ScalaObjectMapperto get rich wrappers that automatically convert scala manifests directly into TypeReferences for Jackson to use (now depecated because manifests are not supported in Scala 3):
scala val mapper = new ObjectMapper() with ScalaObjectMapper mapper.registerModule(DefaultScalaModule) val myMap = mapper.readValue[Map[String,Tuple2[Int,Int]]](src)
This is the equivalent of
scala val mapper = JsonMapper.builder().addModule(DefaultScalaModule).build() val myMap = mapper.readValue(src, new TypeReference[Map[String,Tuple2[Int,Int]]]{})
Consult the Scaladoc for further details.
The master branch often depends on SNAPSHOT versions of the core Jackson projects, which are published to the Sonatype OSS Repository. To make these dependencies available, create a file called
sonatype.sbtin the same directory as
build.sbtwith the following content. The project
.gitignorefile intentionally prevents this file from being checked in.
resolvers += "Sonatype OSS Snapshots" at "https://oss.sonatype.org/content/repositories/snapshots"
Check out Wiki. API Scaladocs can be found on the project site but they are not really well suited to end users, as most classes are implementation details of the module.
The main mechanisms for contribution are:
Currently active core developers (ones who can review, accept and merge Pull Requests) are:
If you have questions on issues, implementation strategies, you may refer to core developers (and this is recommended if you are in doubt!), but keep in mind that these are voluntary positions: everyone is doing this because they want to, not because they are paid or contractually obligated to. This also means that time availability changes over time so getting answers may take time.
In addition other Jackson developers with similar access (but less active) include