Abstract Protected constructorPrivate _globalPrivate Static _globalThe Global Object Store is a place to store global objects that need to be shared across the application. Depending on the execution environment, this could be the window object in a browser, or the global object in a node environment, or something else in other contexts. The key here is that in some cases static variables are not truly shared because it is possible that a given class might have copies of its code in multiple paths in a deployed application. This approach ensures that no matter how many code copies might exist, there is only one instance of the object in question by using the Global Object Store.
Protected Static getReturns the singleton instance of the class. If the instance does not exist, it is created and stored in the Global Object Store. If className is provided it will be used as part of the key in the Global Object Store, otherwise the actual class name will be used. NOTE: the class name used by default is the lowest level of the object hierarchy, so if you have a class that extends another class, the lowest level class name will be used.
Generic, abstract base class for any scenario where we want to use a Singleton pattern. This base class abstracts away the complexity of ensuring a truly global singleton instance across multiple code paths in a deployed application. It uses a Global Object Store to ensure that only one instance of the class exists in the application even if the class has code imported into multiple execution paths (which is not optimal, of course, but can occur in some situations).