Inspired by https://gist.github.com/869408. Forking didn't seem to work :(

LinkBuilder.scala

import scala.collection.mutable.MultiMap
import java.net.URLEncoder
import scala.collection.mutable.{Set => MSet, HashMap, MultiMap}

class LinkBuilder(path: String) {
  val attributes = new HashMap[String, MSet[String]] with MultiMap[String, String] 
  
  override def toString(): String 
    = path +
      "?"  +
      (attributes flatMap { case (name, values) =>
                              values map { name + "=" + URLEncoder.encode(_, "utf-8") }
                          } mkString "&")
        
  def +(name: String, value: String): LinkBuilder = { 
    if (value != null) {
      attributes.addBinding(name, value)
    }   
    this
  }
}