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Scala – retrieve data from XML

Filed in Coding, 22/01/2010, 13:49 by , ,

I started learning Scala 2 months ago, because Groovy’s performance was too low for my purpose -> modelling epidemies on cellular automata.
Appeared a need to throw variables – important for epidemy simulation – to external file.
Scala provides simple interface to use XML data.
Below you can find examples how to retrieve data from XML.
It’s very convenient to work with Scala through console:

scala> x
res5: scala.xml.Elem = 

       0.01
       0.4
       0.5
       
            0.7

Get “init” node in 2 ways:

scala> x \\ "init"
res15: scala.xml.NodeSeq = 0.01

scala> x \ "init"
res16: scala.xml.NodeSeq = 0.01

Get “individual” node in 2 ways:

scala> x \\ "individual"
res17: scala.xml.NodeSeq = 0.7

scala> x \ "die" \ "individual"
res23: scala.xml.NodeSeq = 0.7

Conclusion:

  • “\” is used to search through first level of node’s children
  • “\\” is used to search through every level od node’s children.

Get “init” value :

scala> (x \ "init").text
res19: String = 0.01

scala> (x \ "init").text.toDouble
res20: Double = 0.01

Get “individual” value:

scala> (x \ "die" \ "individual").text
res22: String = 0.7

Similarly you can get attribute:

scala> x \ "recover" \ "@tip"
res28: scala.xml.NodeSeq = const|individual

scala> (x \ "recover" \ "@tip").text
res29: String = const|individual

If you would like to react on specific value in attribute use:

scala> (x \ "recover" \ "@src").text match{
                                            case "const" => true;
                                            case "individual" => false;
                                            case _ => false;
                                        }
res31: Boolean = true