transactions via closures

gistfile1.java

getInvadeStartInstanceTransaction(long defendingPlayerId, long invadingPlayerId, Long defendingPlayerInstanceId, int defendingPlayerFloorCount) {
  return new Transact<InstanceEntity>() {    
    @Override
    public void run(DAOT daot) {
      InstanceEntity instance =
          defendingPlayerInstanceId != null
              ? daot.getInstanceEntity(defendingPlayerInstanceId)
              : new InstanceEntity(defendingPlayerId, defendingPlayerFloorCount);
      instance.addInvadingPlayer(invadingPlayerId);
      instance.setCurrentFloor(invadingPlayerId, 0);
      daot.put(instance);
      result = instance;
    }
  };
}

Transact<InstanceEntity> invadeStart = getInvadeStartTransaction(foo, bar, baz, batz);
// ...
invadeStart.result();