Using Transactions in Constructors
4.1.1. Using transactions in constructors Examples throughout this manual use transactions in the implementation of constructors for new persistent objects. This is deliberate because it guarantees correct propagation of the state of the object to the object store. The state of a modified persistent object is only written to the object store when the top-level transaction commits. Thus, if the constructor transaction is top-level and it commits, the newly-created object is written to the store and becomes available immediately. If, however, the constructor transaction commits but is nested because another transaction that was started prior to object creation is running, the state is written only if all of the parent transactions commit. On the other hand, if the constructor does not use transactions, inconsistencies in the system can arise. For example, if no transaction is active when the object is created, its state is not saved to the store until the next time the object is modified under the control of some transaction.