Scala RegEx Parser Demo

KeyValueParser.scala

import scala.util.parsing.combinator.RegexParsers
import scala.collection.immutable.Map
import scala.util.parsing.combinator.PackratParsers

/**
 * Simple parser for a key value string like:
 * key01 = Value01 key02=value02 key03 =value03 key04= value04
 * 
 * The parser does not support whitespace in key or values.
 */
object KeyValueParser extends RegexParsers {
  
  val emptyMap = Map[String, String]()
  
  def keyValues = rep(keyValue) ^^ {  
    _.foldLeft(emptyMap)((map , pair) => map ++ Map(pair._1 -> pair._2))
  }

  def keyValue  = key ~ value ^^ { 
    case key ~ value => (key, value) 
  }
  
  def key = value ~ eq ^^ { 
    case key ~ eq => key.toString 
  }
  
  def value = whitespace ~ word ~ whitespace ^^ {
    case _ ~ word ~ _ => word.toString
  }
  
  def eq = "=".r
  
  def word = "\\w+".r
  
  def whitespace = "\\s*".r
  
  /**
   * Parse a key value text into a Map[String, String].
   */
  def parse(input: String) = parseAll(keyValues, input) match {
    case Success(result,_)   => result
    case failure : NoSuccess => throw new Exception(failure.msg)
  }
    
}