public Object getPerVMAspect(String def)
{
Object aspect = perVMAspects.get(def);
if (aspect == null)
{
AspectDefinition adef = aspectDefinitions.get(def);
if (adef != null && adef.getScope() == Scope.PER_VM)
{
synchronized (adef)
{
// double check but, now, in a sync block
aspect = perVMAspects.get(def);