if(defaultModelGroup == null) {
synchronized (ERXModel._ERXGlobalModelLock) {
if (defaultModelGroup == null) {
String defaultModelGroupClassName = ERXProperties.stringForKey("er.extensions.defaultModelGroupClassName");
if (defaultModelGroupClassName == null) {
defaultModelGroup = new ERXModelGroup();
}
else {
try {
defaultModelGroup = Class.forName(defaultModelGroupClassName).asSubclass(ERXModelGroup.class).newInstance();
}