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12.5. Overview of JTA Transactions

12.5.1. About Java Transactions API (JTA)

Java Transactions API (JTA) is part of Java Enterprise Edition specification. It is defined in JSR-907.
Implementation of JTA is done using Transaction manager, which is covered by project Narayana for JBoss EAP application server. Transaction manager allows application to assign various resources, for example, database or JMS brokers, through a single global transaction. The global transaction is referred as XA transaction. Only resources with XA capabilities can be included in a transaction.
In this document, JTA refers to Java Transaction API, this term is used to indicate how the transaction manager processes the transactions. Transaction manager works in JTA transactions mode, the data is shared via memory and transaction context is transferred by remote EJB calls. In JTS mode, the data is shared by sending Common Object Request Broker Architecture (CORBA)messages and transaction context is transferred by IIOP calls. Both modes support distribution of transaction over multiple EAP servers.
Annotations is a method for creating and controlling transactions within your code.
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12.5.2. Lifecycle of a JTA Transaction

When a resource asks to participate in a transaction, a chain of events is set in motion. The Transaction Manager is a process that lives within the application server and manages transactions. Transaction participants are objects which participate in a transaction. Resources are datasources, JMS connection factories, or other JCA connections.

  1. Your application starts a new transaction

    To begin a transaction, your application obtains an instance of class UserTransaction from JNDI or, if it is an EJB, from an annotation. The UserTransaction interface includes methods for beginning, committing, and rolling back top-level transactions. Newly-created transactions are automatically associated with their invoking thread. Nested transactions are not supported in JTA, so all transactions are top-level transactions.
    Calling UserTransaction.begin() using annotations starts a transaction when an EJB method is called (driven by TransactionAttribute rules). Any resource that is used after that point is associated with the transaction. If more than one resource is enlisted, your transaction becomes an XA transaction, and participates in the two-phase commit protocol at commit time.

    Note

    The UserTransaction object is used only for BMT transactions. In CMT, the UserTransaction object is not permitted.

  2. Your application modifies its state.

    In the next step, your application performs its work and makes changes to its state.

  3. Your application decides to commit or roll back

    When your application has finished changing its state, it decides whether to commit or roll back. It calls the appropriate method, either UserTransaction.commit() or UserTransaction.rollback().

  4. The transaction manager removes the transaction from its records.

    After the commit or rollback completes, the transaction manager cleans up its records and removes information about your transaction from the transaction log.
Failure recovery

Failure recovery happens automatically. If a resource, transaction participant, or the application server become unavailable, the Transaction Manager handles recovery when the underlying failure is resolved and the resource is available again.

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