Scala HyperGraphDB-Transaction Utility methods + tests

ScalaHGDBTransactions.scala

object TestTransa {
import org.hypergraphdb.transaction.HGUserAbortException
import scala.runtime.NonLocalReturnControl
import org.hypergraphdb._
import HGQuery.hg
import java.lang.Throwable
import scala.annotation.tailrec


val graph:HyperGraph = new HyperGraph("/home/ingvar/bin/sbt-scala-hypergraphdb/bje")

def main(args:Array[String]) =
{
   val b :Either[Throwable,String]= transact[String](Unit => { graph.get(graph.add("Hello World")).asInstanceOf[String] })
   val d: String= transact2T[String](Unit => { graph.get(graph.add("Hello World")).asInstanceOf[String] })

   println("funtional transact result: " + b)
   println("transact result returning T: " + d)
   graph.close
}

// transaction method returning Either[Throwable,T]
def transact[T](code: Unit => T):Either[Throwable,T] =
{
   //shorthands
   def retryThrow(t:Throwable):Boolean = graph.getStore().getTransactionFactory().canRetryAfter(t);
   def commit(b:Boolean) = try{ graph.getTransactionManager().endTransaction(b); } catch { case e => if (retryThrow(e)) throw(e) }

   @tailrec def transactInt[T](code: Unit => T):Either[Throwable,T] =
   {
   ( try {
   graph.getTransactionManager().beginTransaction()
   Right(code())
         } catch { case e:Throwable => Left(e) }
   ) match {
      case e: Right[Throwable,T] => commit(true) ; e
      case l1: Left[NonLocalReturnControl[T],Int]	=> commit(true) ; Right(l1.left.get.value)
      case l2: Left[HGUserAbortException,T]	=> commit(false); l2
      case t: Left[Throwable,T] => commit(false); if (retryThrow(t.left.get)) throw(t.left.get) else transactInt(code)
         }
   }
transactInt(code)
}


// transaction method returning T
def transact2T[T](code: Unit => T):T = {
   //shorthands
   def retryThrow(t:Throwable):Boolean = graph.getStore().getTransactionFactory().canRetryAfter(t);
   def commit(b:Boolean) = try{ graph.getTransactionManager().endTransaction(b); } catch { case e => if (retryThrow(e)) throw(e) }

   @tailrec def transact2TInt[T](code: Unit => T):T = {
   ( try {
      graph.getTransactionManager().beginTransaction()
      Right(code())
         } catch { case e:Throwable => Left(e) }
   ) match {
      case Right(r) => commit(true) ; r
      case l1: Left[NonLocalReturnControl[T],Int]	=> commit(true) ; l1.left.get.value
      case l2: Left[HGUserAbortException,T]	=> commit(false); null.asInstanceOf[T]
      case t: Left[Throwable,T] => commit(false); if (retryThrow(t.left.get)) throw(t.left.get) else transact2TInt(code)
      }  
   }
   transact2TInt(code)
}
}

in response to this blogpost: http://scalahypergraph.blogspot.de/2012/11/scala-closures-as-hypergraphdb.html