Automatic XML printing for case classes in Scala. Tested with Scala 2.10.3.

Output.xml

<Human>
  <title>Mr.</title>
  <name>Johnny</name>
  <coats>
    <Coat>
      <brand>BOSS</brand>
    </Coat>
    <Coat>
      <brand xsi:nil="true"/>
    </Coat>
    <Coat>
      <brand>Armani</brand>
    </Coat>
  </coats>
</Human>
<list>
  <list>
    <item>a</item>
    <item>b</item>
  </list>
  <list>
    <item>5</item>
    <item>6</item>
  </list>
  <list>
    <item>
      <Human>
        <title>Mr.</title>
        <name>Johnny</name>
        <coats>
          <Coat>
            <brand>BOSS</brand>
          </Coat>
          <Coat>
            <brand xsi:nil="true"/>
          </Coat>
          <Coat>
            <brand>Armani</brand>
          </Coat>
        </coats>
      </Human>
    </item>
    <item>
      <Human>
        <title>Mr.</title>
        <name>Johnny</name>
        <coats>
          <Coat>
            <brand>BOSS</brand>
          </Coat>
          <Coat>
            <brand xsi:nil="true"/>
          </Coat>
          <Coat>
            <brand>Armani</brand>
          </Coat>
        </coats>
      </Human>
    </item>
  </list>
</list>
<Human>
  <title>Mr.</title>
  <name>Johnny</name>
  <coats>
    <Coat>
      <brand>BOSS</brand>
    </Coat>
    <Coat>
      <brand xsi:nil="true"/>
    </Coat>
    <Coat>
      <brand>Armani</brand>
    </Coat>
  </coats>
</Human>
<list>
  <list>
    <item>a</item>
    <item>b</item>
  </list>
  <list>
    <item>5</item>
    <item>6</item>
  </list>
  <list>
    <item>
      <Human>
        <title>Mr.</title>
        <name>Johnny</name>
        <coats>
          <Coat>
            <brand>BOSS</brand>
          </Coat>
          <Coat>
            <brand xsi:nil="true"/>
          </Coat>
          <Coat>
            <brand>Armani</brand>
          </Coat>
        </coats>
      </Human>
    </item>
    <item>
      <Human>
        <title>Mr.</title>
        <name>Johnny</name>
        <coats>
          <Coat>
            <brand>BOSS</brand>
          </Coat>
          <Coat>
            <brand xsi:nil="true"/>
          </Coat>
          <Coat>
            <brand>Armani</brand>
          </Coat>
        </coats>
      </Human>
    </item>
  </list>
</list>

TypeMagic.scala

package com.v.utils

object TypeMagic {

  import scala.tools.scalap.scalax.rules.scalasig.MethodSymbol
  import scala.reflect.runtime.universe._

  class Memoize1[-T, +R](f: T => R) extends (T => R) {
    private[this] val vals = scala.collection.mutable.Map.empty[T, R]
    def apply(x: T): R = vals.getOrElseUpdate(x, f(x))
  }

  def getType[T](clazz: Class[T])(implicit runtimeMirror: Mirror) =
    runtimeMirror.classSymbol(clazz).toType

  implicit val mirror = runtimeMirror(getClass.getClassLoader)

  type productable[T] = Class[T with Product]
  def getFieldsL(clazz: productable[_]) = this.synchronized {{
    val args = getType(clazz).member(nme.CONSTRUCTOR).asMethod.paramss.head
    val argNames = for ( a <- args ) yield a.name.decoded
    for {
      field <- clazz.getDeclaredFields
      name = field.getName
      if argNames contains name
    } yield (name, field)
  }.toMap}

  def makeFieldGetterF(fields: Map[String, java.lang.reflect.Field]):(Product => Map[String, Any]) =
    (input: Product) => {
      for {
        (name, field) <- fields.toSeq
        madeAccessible = field.setAccessible(true)
        value = field.get(input)
      }
      yield (name, value) }.toMap


  def makeFieldGetter[T<:Product](clazz:productable[_]) = makeFieldGetterF(getFieldsL(clazz))

  val getFieldGetter = new Memoize1(makeFieldGetter)

  def getFields(a: Product) = getFieldGetter(a.getClass.asInstanceOf[productable[_]])(a)

  val getFieldsOf = getFields(_)
}

XmlPrinting.scala

package com.v.utils

object XmlPrinting {
  object HeadNode {
    implicit def headNode(nodes: Traversable[scala.xml.Node]):scala.xml.Node = nodes.head
  }

  import TypeMagic.getFieldsOf

  implicit class pretty[A](a:A) {

    def xmlString: Traversable[scala.xml.Node] = a match {
      case list: Traversable[_] =>
        <list>{list.collect{
          case subList: Traversable[_] => subList.xmlString
          case item=>{<item>{item.childXmlString}</item>}
        }}</list>
      case x:Any => x.childXmlString
    }

    def childXmlString: Traversable[scala.xml.Node] = a match {
      case list: Traversable[_] =>
        for ( item <- list; sub <- item.childXmlString )
        yield sub
      case product: Product =>
        <node>{
          for {
            (title, value) <- getFieldsOf(product)
            base = <node/>.copy(label = title)
          } yield value match {
            case Some(x) => base.copy(child = x.childXmlString.toSeq)
            case None => <node xsi:nil="true"/>.copy(label = title)
            case x => base.copy(child = x.childXmlString.toSeq)
          }
          }</node>.copy(label=product.productPrefix)
      case null =>
          <nil xsi:nil="true"/>
      case x => scala.xml.Text(x.toString)
    }
  }


}

XmlPrintingTest.scala

package com.v.utils

/**
 * 
 * Scala XML object printing example.
 * 2013 - William Narmontas https://vynar.com/
 * 
 */

/*
Relevant:
 1. http://stackoverflow.com/questions/15067872/get-scala-type-for-a-java-lang-classt-in-scala-2-10
 2. http://docs.scala-lang.org/overviews/reflection/overview.html
 3. http://www.encodedknowledge.com/2013/01/scala-2-10-reflection-experiments/
 4. http://stackoverflow.com/questions/4697534/knowing-if-a-scala-object-is-an-instance-of-case-class
 5. http://stackoverflow.com/questions/7525142/how-to-programmatically-determine-if-the-the-class-is-a-case-class-or-a-simple-c
 6. http://stackoverflow.com/questions/15730155/why-dont-scala-case-class-fields-reflect-as-public
 7. http://stackoverflow.com/questions/2224251/reflection-on-a-scala-case-class
 8. http://stackoverflow.com/questions/16079113/scala-2-10-reflection-how-do-i-extract-the-field-values-from-a-case-class
 9. http://stackoverflow.com/questions/15718506/scala-how-to-print-case-classes-like-pretty-printed-tree
10. https://github.com/nikita-volkov/sext/blob/master/src/main/scala/sext/package.scala#L118-L173
11. https://github.com/nikita-volkov/sext
12. http://stackoverflow.com/questions/15718506/scala-how-to-print-case-classes-like-pretty-printed-tree
13. https://github.com/ymasory/labeled-tostring
14. http://docs.scala-lang.org/tutorials/tour/case-classes.html
 */

object XmlPrintingTest extends App {

  import XmlPrinting._

  import HeadNode.headNode

  case class Coat(brand: Option[String])

  case class Human(title: String, name: String, coats: Seq[Coat])

  val human = Human("Mr.", "Johnny", List(Coat(Option("BOSS")), Coat(None), Coat(Option("Armani"))))

  val printer = new scala.xml.PrettyPrinter(80, 2)


  println(printer.format(human.xmlString))
  println(printer.format(List(List("a","b"),List(5,6),List(human,human)).xmlString))
  println(printer.format(human.xmlString))
  println(printer.format(List(List("a","b"),List(5,6),List(human,human)).xmlString))

}