Java Data Objects

Making a Persistent Instance Transient

Suppose you have a persistent instance that you want to make accessible to a client application via Remote Method Invocation (RMI). Suppose your code is executing in a Common Object Request Broker Architecture (CORBA) or application-server environment, where the transaction context will no longer exist once your servlet or session bean returns from a client invocation. When RMI serializes your instance, the transaction is no longer active. You do not want the PersistenceManager to mediate access to a persistent instance outside of a transaction context. So, to pass the persistent instance to a remote client, you must convert it into a transient instance. This is necessary to disassociate the instance with the PersistenceManager, so field access is not mediated.

You do this by making the persistent instance transient. You can use the following PersistenceManager methods to make persistent instances transient:

void makeTransient(Object obj);
void makeTransientAll(Object[] objs);
void makeTransientAll(Collection objs);

When the instances transition to transient, they lose their identity and association with the PersistenceManager. They are no longer associated with their representation in the datastore, so their in-memory state does not affect the persistent state in the datastore. Even though the instance in memory is transient, the instance still exists in the datastore. Making a persistent instance transient is not equivalent to calling deletePersistent( ...