Java Data Objects

Retaining Values at Transaction Commit

We have seen how reading data outside a transaction results in caching nontransactional instances. Another way for nontransactional instances to exist in the cache is to execute a transaction and then retain the field values at commit time. You can specify this behavior by setting the RetainValues property to true. This is shown in Figure 14-2.

Figure 14-2. RetainValues at transaction commit

With RetainValues set to true, persistent transactional instances transition to persistent-nontransactional at commit. But with RetainValues set to false, fields of persistent transactional instances are cleared at transaction commit, and the instances transition to hollow.

The result is that your application can use the cached instances between transactions, and the instances used in the transaction retain their last-committed values. Instances not used in transactions remain nontransactional.

Since the RetainValues flag only affects the behavior of transaction commit( ), your application can change it at any time, using setRetainValues( ) in Transaction. Regardless of how many times the value changes, the value currently in effect at commit is used.