9.2.4. The Life cycle of a Transactional Object for Java

A persistent object which is not in use is assumed to be in a passive state, with its state residing in an object store and activated on demand. See the Figure 9.2, “Fundamental Life cycle of a Persistent Object in TXOJ”.
Fundamental Life cycle of a Persistent Object in TXOJ

Figure 9.2. Fundamental Life cycle of a Persistent Object in TXOJ

  • The object is initially passive, and is stored in the object store as an instance of the class OutputObjectState.
  • When required by an application, the object is automatically activated by reading it from the store using a read_committed operation and is then converted from an InputObjectState instance into a fully-fledged object by the restore_state operation of the object.
  • When the application finishes with the object, it is deactivated by converting it back into an OutputObjectState instance using the save_state operation, and is then stored back into the object store as a shadow copy using the write_uncommitted method. This shadow copy can be committed, overwriting the previous version, using the commit_state operation. The existence of shadow copies is normally hidden from the programmer by the transaction system. Object de-activation normally only occurs when the top-level transaction within which the object was activated commits.

Note

During its lifetime, a persistent object may change from passive to active and back again, many times.