Java Data Objects

Transactions

Accesses and updates to persistent instances are performed in the context of a transaction. The JDO Transaction interface provides the methods you use to begin and commit a transaction. It also has methods to manage the settings of transaction flags. It is similar in functionality to a javax.transaction.UserTransaction . Both interfaces have begin( ), commit( ), and rollback( ) methods with the same semantics and behavior.

A one-to-one relationship exists between a PersistenceManager and its associated Transaction instance. A PersistenceManager instance represents a single view of persistent data, including persistent instances that have been cached across multiple serial transactions. If your application needs multiple concurrent transactions, each transaction will have its own Transaction instance and associated PersistenceManager instance.

You call methods in the JDO Transaction interface to perform operations on a transaction. The underlying datastore has its own representation for a transaction, with its own operations and interfaces. JDO supports a type of transaction referred to as a datastore transaction. This is not the transaction in the underlying datastore. We refer to the transaction at the datastore level as the transaction in the datastore, to distinguish it from the JDO datastore transaction.

Properties of Transactions

Transactions have a set of common properties that are referred to as the ACID (Atomic, Consistent, Isolated, Durable) properties of a transaction. ...