JAXB-based XML and JSON APIs

jaxb-01.scala

import javax.xml.bind.annotation._

@XmlRootElement(name = "person")
@XmlAccessorType(XmlAccessType.FIELD)
case class Person(fullname: String, username: Option[String], age: Int)

jaxb-02.scala

import scala.annotation.target.field

import javax.xml.bind.annotation._
import javax.xml.bind.annotation.adapters._

type xmlElement     = XmlElement @field
type xmlTypeAdapter = XmlJavaTypeAdapter @field

class StringOptionAdapter extends OptionAdapter[String](null, "")
class OptionAdapter[A](nones: A*) extends XmlAdapter[A, Option[A]] {
  def marshal(v: Option[A]): A = v.getOrElse(nones(0))
  def unmarshal(v: A) = if (nones contains v) None else Some(v)
}

@XmlRootElement(name = "person")
@XmlAccessorType(XmlAccessType.FIELD)
case class Person(
    @xmlElement(required=true) fullname: String, 
    @xmlTypeAdapter(classOf[StringOptionAdapter]) username: Option[String], 
    age: Int) {
  // only needed and accessed by JAXB
  private def this() = this("", None, 0)
}

jaxb-03.scala

import javax.xml.bind._
import javax.xml.transform.stream.StreamResult

val context = JAXBContext.newInstance(classOf[Person])

context.generateSchema(new SchemaOutputResolver {
  def createOutput(namespaceUri: String, suggestedFileName: String) = {
    val res = new StreamResult(System.out)
    res.setSystemId(suggestedFileName)
    res
  }
})

jaxb-04.xsd

<xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="person" type="person"/>
  <xs:complexType name="person">
    <xs:sequence>
      <xs:element name="fullname" type="xs:string"/>
      <xs:element name="username" type="xs:string" minOccurs="0"/>
      <xs:element name="age" type="xs:int"/>
    </xs:sequence>
  </xs:complexType>
</xs:schema>

jaxb-05.scala

context.createMarshaller.marshal(Person("Martin Krasser", Some("krasserm"), 30 /* haha */), System.out)

jaxb-06.xml

<person>
  <fullname>Martin Krasser</fullname>
  <username>krasserm</username>
  <age>30</age>
</person>

jaxb-07.scala

val personXml1 = "<person><fullname>Martin Krasser</fullname><age>30</age></person>"
val personXml2 = "<person><fullname>Martin Krasser</fullname><username>mrt1nz</username><age>30</age></person>"

assert(context.createUnmarshaller().unmarshal(new StringReader(personXml1)) == 
  Person("Martin Krasser", None, 30))

assert(context.createUnmarshaller().unmarshal(new StringReader(personXml2)) == 
  Person("Martin Krasser", Some("mrt1nz"), 30))

jaxb-08.scala

import com.sun.jersey.api.json._

val config = JSONConfiguration.natural().rootUnwrapping(false).build()
val context = new JSONJAXBContext(config, classOf[Person])

context.createJSONMarshaller().marshallToJSON(person, System.out)

jaxb-09.json

{"person":{"fullname":"Martin Krasser","username":"krasserm","age":30}}