Resolving geographical entities with Scala

Ilya Boyandin — Thu, 17 Jun 2010 09:25:00 +0000

Here is a chunk of Scala code for getting lat/lon coordinates of geographical locations (cities or villages) using the wonderful geonames.org webservice which allows to search for geo entities by name. The getCoords() method returns a triple of (resolved entity name, lat, lon). The countryCode parameter is optional and will limit the search within the country when specified. The webservice often returns more than one result, in this case the method will return the coordinates of the first one.

import scala.xml._
import java.io._
import java.net.{URLEncoder, URL}
 
def getCoords(query:String, countryCode:String):(String, Double, Double) = {
  val geonames = XML.loadString(readUrl(
    "http://ws.geonames.org/search?featureClass=P&q=" + URLEncoder.encode(query) +
            (if (countryCode != null) ("&country=" + countryCode) )))
 
  if ((geonames \ "geoname").size  > 0) {
    var firstGeoname = (geonames \ "geoname").first
 
    ((firstGeoname \ "name").first.text + " (" +
          (firstGeoname \ "countryCode").first.text + ")",
     (firstGeoname \ "lat").first.text.toDouble,
     (firstGeoname \ "lng").first.text.toDouble)
  } else {
    null
  }
}
 
def readUrl(url:String) = {
  val in = new BufferedReader(new InputStreamReader(new URL(url).openStream(), "utf-8"))
  val response = new StringBuilder
  var inputLine:String = null
  do {
    inputLine = in.readLine
    if (inputLine != null) response.append(inputLine)
  } while (inputLine != null)
  in.close
 
  response.toString
}

Calling getCoords(“Neuchatel”, “CH”) returns a triple (Neuchâtel (CH),46.99179,6.931).

Ilya Boyandin » scala

Resolving geographical entities with Scala