Oracle GlassFish Server 3.0.1 Application Development Guide

Handling Transactions With Enterprise Beans

This section describes the transaction support built into the Enterprise JavaBeans programming model for the GlassFish Server.

As a developer, you can write an application that updates data in multiple databases distributed across multiple sites. The site might use EJB servers from different vendors. This section provides overview information on the following topics:

Flat Transactions

The Enterprise JavaBeans Specification, v3.0 requires support for flat (as opposed to nested) transactions. In a flat transaction, each transaction is decoupled from and independent of other transactions in the system. Another transaction cannot start in the same thread until the current transaction ends.

Flat transactions are the most prevalent model and are supported by most commercial database systems. Although nested transactions offer a finer granularity of control over transactions, they are supported by far fewer commercial database systems.

Global and Local Transactions

Understanding the distinction between global and local transactions is crucial in understanding the GlassFish Server support for transactions. See Transaction Scope.

Both local and global transactions are demarcated using the javax.transaction.UserTransaction interface, which the client must use. Local transactions bypass the transaction manager and are faster. For more information, see The Transaction Manager, the Transaction Synchronization Registry, and UserTransaction.

Commit Options

The EJB protocol is designed to give the container the flexibility to select the disposition of the instance state at the time a transaction is committed. This allows the container to best manage caching an entity object’s state and associating an entity object identity with the EJB instances.

There are three commit-time options:

The GlassFish Server deployment descriptor has an element, commit-option, that specifies the commit option to be used. Based on the specified commit option, the appropriate handler is instantiated.

Administration and Monitoring

An administrator can control a number of domain-level Transaction Service settings. For details, see Configuring the Transaction Service.

The Transaction Timeout setting can be overridden by a bean. See Bean-Level Container-Managed Transaction Timeouts.

In addition, the administrator can monitor transactions using statistics from the transaction manager that provide information on such activities as the number of transactions completed, rolled back, or recovered since server startup, and transactions presently being processed.

For information on administering and monitoring transactions, select the Transaction Service component under the relevant configuration in the Administration Console and click the Help button. Also see Chapter 21, Administering Transactions, in Oracle GlassFish Server 3.0.1 Administration Guide.