Understanding Distributed Transactions

Transactions against a single database are handled quite cleanly by the commit() and rollback() methods of the JDBC Connection object. An example of this was shown in Listing 16.1. J2EE applications often have much more complex transactions resulting from their distributed nature. For example, the same transaction may span multiple tiers, possibly shared by the servlet and EJB. Also, multiple databases may be involved in the same transaction. Such transactions are referred to as distributed transactions . The Java Transaction API (JTA) provides the ability to handle distributed transactions. The WebLogic services specifically designed for distributed transactions work with JTA, XA-compliant resources, and Two-Phase Commit (2PC) operations. These topics are addressed in the section "Performing Distributed Transactions with a Transaction Manager," later in this chapter.