GAE JCache NumberFormatException, will I need to write Java to avoid?

Question

The code below produces a NumberFormatException in this line:

val cache = cf.createCache(Collections.emptyMap())

Do you see any errors?
Will I need to write a Java version to avoid this, or is there a Scala way?

...
import java.util.Collections
import net.sf.jsr107cache._

object QueryGenerator extends ServerResource {
  private val log = Logger.getLogger(classOf[QueryGenerator].getName)
}

class QueryGenerator extends ServerResource {
  def getCounter(cache:Cache):long = {
      if (cache.containsKey("counter")) {
        cache.get("counter").asInstanceOf[long]
      } else {
        0l
      }
    }

  @Get("html")
  def getHtml(): Representation = {
    val cf = CacheManager.getInstance().getCacheFactory()
    val cache = cf.createCache(Collections.emptyMap())

    val counter = getCounter(cache)

    cache.put("counter", counter + 1)

    val q = QueueFactory.getQueue("query-generator")
    q.add(TaskOptions.Builder.url("/tasks/query-generator").method(Method.GET).countdownMillis(1000L))

    QueryGenerator.log.warning(counter.toString)

    new StringRepresentation("QueryGenerator started!", MediaType.TEXT_HTML)
  }
}

Thanks!

Answer 1

I suspect that the exception is really happening in the call to getCounter. NumberFormatException is thrown when you try to convert a String to a number, and that String does not contain a recognizable number.

Answer 2

I have added a small Java Class for the putting/updating now. Not the most elegant solution, but it works. A Scala solution would still be appreciated.

Java:

import javax.cache.Cache;

public class CacheHelper {
    public static final void update(Cache cache,String key,Object value) {
        cache.put(key,value);
    }
}

Scala:

import java.util.Collections
import javax.cache.CacheManager
import somewhere.CacheHelper

object QueryGenerator extends ServerResource {
  private val log = Logger.getLogger(classOf[QueryGenerator].getName)
}

class QueryGenerator extends ServerResource {

  @Get("html")
  def getHtml(): Representation = {
    val cf = CacheManager.getInstance().getCacheFactory()
    val cache = cf.createCache(Collections.emptyMap())

    val counter = if (cache.containsKey("counter")) {
      cache.get("counter").asInstanceOf[Int]
    } else {
      0
    }

    CacheHelper.update(cache,"counter",counter+1)

    val q = QueueFactory.getQueue("query-generator")
    q.add(TaskOptions.Builder.url("/tasks/query-generator").method(Method.GET).countdownMillis(1000L))

    QueryGenerator.log.warning(counter.toString())

    new StringRepresentation("QueryGenerator started!", MediaType.TEXT_HTML)
  }
}